Considerations for improving assay sensitivity in chronic pain clinical trials: IMMPACT recommendations

Evidence-based hierarchy of pain outcome measures for osteoarthritis clinical trials and meta-analyses

OBJECTIVE

To rank commonly used patient-reported outcome measures (PROMs) for assessing pain in osteoarthritis trials according to their assay sensitivity, defined as the ability of a PROM to distinguish an effective from a less effective intervention or placebo, proposing a hierarchy for PROM selection in trials and data-extraction in meta-analyses.

DESIGN

Analysis of trials with placebo, sham, or non-intervention control that included ≥100 patients per arm with knee/hip osteoarthritis, reporting treatment effects on ≥2 pain PROMs. Treatment effects from all PROMs were standardized on a 0-100 scale. Negative mean differences indicated a larger effect of the experimental treatment compared to control. We ranked PROMs by assay sensitivity using a Bayesian multi-outcome synthesis random-effects model.

RESULTS

135 trials comprising 57,141 participants were included. The ranking of PROMs from highest to lowest assay sensitivity was as follows: pain overall, pain on stairs, pain at night, pain on walking, pain at rest, WOMAC pain, WOMAC global, Lequesne index. Pain overall, the highest-ranked PROM, had a pooled mean difference of -6.96 (95%CrI -7.94, -6.02), while WOMAC pain, the most reported PROM in our study, had a pooled mean difference of -4.90 (95%CrI -5.55, -4.26). The pooled ratio of mean differences between pain overall and WOMAC pain was 1.42 (95%CrI 1.30, 1.55), representing a 42% larger effect size with pain overall.

CONCLUSIONS

Pain overall has better assay sensitivity than other pain PROMs. Investigators should consider the hierarchy proposed in this study to guide PROM selection in osteoarthritis clinical trials and data extraction in osteoarthritis meta-analyses.

A Phase 3, Multicenter, Randomized, Double-Blind, Placebo-Controlled 14-Week Study of Mirogabalin in Chinese Patients with Diabetic Peripheral Neuropathic Pain

INTRODUCTION

There is no approved effective drug for diabetic peripheral neuropathic pain (DPNP) in China. Gabapentinoids including mirogabalin have shown promise, although data in Chinese patients are scarce.

METHODS

This phase 3, multicenter, randomized, double-blind, placebo-controlled trial investigated the efficacy and safety of mirogabalin for treating DPNP in China. Mirogabalin was administered at 5 mg twice daily for the first week and uptitrated to 15 mg twice daily for a total duration of 14 weeks. The primary efficacy endpoint was the change from baseline in weekly average daily pain score (ADPS) at week 14; secondary endpoints included the ADPS responder rate, Short-Form McGill Pain Questionnaire visual analogue scale score, patient global impression of change (PGIC), average daily sleep interference score (ADSIS), EuroQol 5-dimensions 5-levels (EQ-5D-5L), and incidence of treatment-emergent adverse events (TEAEs).

RESULTS

Of 393 patients (mirogabalin, n = 196; placebo n = 197), the mean age was 58.2 years (mirogabalin, 58.7 years; placebo, 57.7 years) and 54.2% were male (mirogabalin, 56.1%; placebo, 52.3%). Mirogabalin elicited a greater change from baseline in the weekly ADPS vs. placebo at week 14: least-squares mean difference (95% confidence interval) vs. placebo - 0.39 (- 0.74, - 0.04), p = 0.0301. PGIC, ADSIS, and EQ-5D-5L data reflected significantly better improvements for patients receiving mirogabalin vs. placebo. The incidence of TEAEs was 75.0% and 75.1% in the mirogabalin and placebo groups, respectively. Most TEAEs were mild or moderate, and the incidence of TEAEs leading to treatment discontinuation was 2.6% in the mirogabalin group and 1.5% in the placebo group.

CONCLUSIONS

Although the effect size of mirogabalin was reduced due to the placebo effect, mirogabalin is a safe and effective treatment option for Chinese patients with DPNP.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT04094662.

Counting your chickens before they hatch: improvements in an untreated chronic pain population, beyond regression to the mean and the placebo effect

Introduction

Isolating the effect of an intervention from the natural course and fluctuations of a condition is a challenge in any clinical trial, particularly in the field of pain. Regression to the mean (RTM) may explain some of these observed fluctuations.

Objectives

In this paper, we describe and quantify the natural trajectory of questionnaire scores over time, based on initial scores.

Methods

Twenty-seven untreated chronic low back pain patients and 25 healthy controls took part in this observational study, wherein they were asked to complete an array of questionnaires commonly used in pain studies during each of 3 visits (V1, V2, V3) at the 2-month interval. Scores at V1 were classified into 3 subgroups (extremely high, normal, and extremely low), based on z-scores. The average delta (∆ = V2 - V1) was calculated for each subgroup, for each questionnaire, to describe the evolution of scores over time based on initial scores. This analysis was repeated with the data for V2 and V3.

Results

Our results show that high initial scores were widely followed by more average scores, while low initial scores tended to be followed by similar (low) scores.

Conclusion

These trajectories cannot be attributable to RTM alone because of their asymmetry, nor to the placebo effect as they occurred in the absence of any intervention. However, they could be the result of an Effect of Care, wherein participants had meaningful improvements simply from taking part in a study. The improvement observed in patients with high initial scores should be carefully taken into account when interpreting results from clinical trials.

Does opioid therapy enhance quality of life in patients suffering from chronic non-malignant pain? A systematic review and meta-analysis

Background and objective

Chronic pain is associated with a poor health-related quality of life (HRQL). Whereas the prescription rate of opioids increased during the last decades, their use in chronic non-malignant pain remains unclear. However, there is currently no clinical consensus or evidence-based guidelines that consider the long-term effects of opioid therapy on HRQL in patients with chronic non-cancer pain. This systematic review aims to address the question of whether opioid therapy improves HRQL in patients with chronic non-malignant pain and provide some guidance to practitioners.

Databases and data treatment

PubMed, EMBASE and CENTRAL were searched in June 2020 for double-blind, randomized trials (RCTs), comparing opioid therapy to placebo and assessed a HRQL questionnaire. The review comprises a qualitative vote counting approach and a meta-analysis of the Short Form Health Survey (SF-36), EQ-5D questionnaire and the pain interference scale of the Brief pain inventory (BPI).

Results

35 RCTs were included, of which the majority reported a positive effect of opioids for the EQ-5D, the BPI and the physical component score (PCS) of the SF-36 compared to placebo. The meta-analysis of the PCS showed a mean difference of 1.82 [confidence interval: 1.32, 2.32], the meta-analysis of the EQ-5D proved a significant advantage of 0.06 [0.00, 0.12]. In the qualitative analysis of the mental component score (MCS) of the SF-36, no positive or negative trend was seen. No significant differences were seen in the MCS (MD: 0.65 [-0.43, 1.73]). A slightly higher premature dropout rate was found in the opioid group (risk difference: 0.04 [0.00, 0.07], p = .07). The body of evidence is graded as low to medium.

Conclusion

Opioids have a statistically significant, but small and clinical not relevant effect on the physical dimensions of HRQL, whereas there is no effect on mental dimensions of HRQL in patients with chronic non-malignant pain during the initial months of treatment. In clinical practice, opioid prescriptions for chronic non-cancer pain should be individually assessed as their broad efficacy in improving quality of life is not confirmed. The duration of opioid treatment should be determined carefully, as this review primarily focuses on the initial months of therapy.

What Is Behind? Impact of Pelvic Pain on Perceived Stress and Inflammatory Markers in Women with Deep Endometriosis

Introduction/Objectives: Endometriosis affects 10% of women worldwide. It is noteworthy that this condition is often accompanied by pelvic pain and stress. Endometriosis is a debilitating gynecological condition where tissue similar to the uterine lining grows outside the uterus, often causing significant pain and reproductive issues. We aimed to study the relationship between the intensity of pelvic pain, and stress and inflammatory markers in women with deep endometriosis. Methods: This cross-sectional study analyzed women diagnosed with deep endometriosis through imaging, surgery, and/or biopsy. We assessed pain using the Numerical Rating Scale (NRS). Stress was assessed with the Perceived Stress Scale (PSS-10) questionnaire and the serum cortisol levels. Additionally, we analyzed inflammatory markers, including C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Results: Fifty-two women, with an average age of 37.8 ± 6.9 years, participated in this study. Forty-four percent of these participants demonstrated high levels of stress, as indicated by scores above 26 on the PSS-10. Those categorized with "high stress" on the PSS-10 questionnaire exhibited significantly higher pain levels compared to those with "low stress" (p < 0.05). Furthermore, patients experiencing more-severe pelvic pain (pain score > 7) had notably higher serum cortisol levels. Women with intense pelvic pain (scores above 7 on the NRS) had significantly elevated serum cortisol levels (Cohen's d = 0.72; p = 0.018). Conclusions: A positive association was found between stress levels and the intensity of pelvic pain in women with deep endometriosis, suggesting an interconnection between emotional aspects and biological responses.

Wireless Transcutaneous Electrical Nerve Stimulation (TENS) for Chronic Chemotherapy-Induced Peripheral Neuropathy (CIPN): A Proof-of-Concept Randomized Clinical Trial

Chemotherapy-induced peripheral neuropathy (CIPN) affects approximately 30 to 60% of people who receive neurotoxic chemotherapy. CIPN is associated with impaired quality of life and function and has few effective treatments. This 6-site, subject and assessor-blinded randomized clinical trial (RCT) was designed to assess 1) preliminary efficacy (ie, alpha pre-specified at .2) of a wearable, app-controlled, transcutaneous electrical nerve stimulation (TENS) device for chronic CIPN and 2) feasibility of conducting a confirmatory trial within the National Cancer Institute Community Oncology Research Program (NCORP) (NCT04367480). The primary outcome was the EORTC-CIPN20. The main secondary outcomes were individual symptoms assessed daily (via 0-10 numeric rating scales). The primary analysis was an analysis of covariance (outcome: EORTC-CIPN20, fixed effect: arm, covariates: baseline EORTC-CIPN20 and site). Secondary analyses used a similar analysis of covariance models (excluding site) for each symptom on subgroups of subjects with ≥4 out of 10 for that symptom at baseline. 142 eligible subjects were randomized and received a device; 130 (91%) completed the study. The difference between groups in the EORCT-CIPN20 at the endpoint (placebo-active) was 1.05 (95% Confidence Interval: -.56, 2.67; P = .199). The difference between groups for the individual symptoms was as follows: hot/burning pain: 1.37 (-.33, 3.08; P = .112), sharp/shooting pain: 1.21 (-.37, 2.79; P = .128), cramping: 1.35 (-.32, 3.02; P = .110), tingling: .23 (-.61, 1.08; P = .587), numbness: .27 (-.51, 1.05; P = .492). An RCT of an app-controlled TENS device for chronic CIPN with excellent retention is feasible in the NCORP. Preliminary efficacy evidence suggests that TENS is promising for pain and cramping from CIPN. A confirmatory RCT of TENS for painful CIPN is highly warranted. PERSPECTIVE: Daily, home-based TENS therapy demonstrates promising efficacy for painful CIPN symptoms in this proof-of-concept randomized clinical trial. Future confirmatory trial is warranted.

Patient engagement in designing, conducting, and disseminating clinical pain research: IMMPACT recommended considerations

ABSTRACT

In the traditional clinical research model, patients are typically involved only as participants. However, there has been a shift in recent years highlighting the value and contributions that patients bring as members of the research team, across the clinical research lifecycle. It is becoming increasingly evident that to develop research that is both meaningful to people who have the targeted condition and is feasible, there are important benefits of involving patients in the planning, conduct, and dissemination of research from its earliest stages. In fact, research funders and regulatory agencies are now explicitly encouraging, and sometimes requiring, that patients are engaged as partners in research. Although this approach has become commonplace in some fields of clinical research, it remains the exception in clinical pain research. As such, the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials convened a meeting with patient partners and international representatives from academia, patient advocacy groups, government regulatory agencies, research funding organizations, academic journals, and the biopharmaceutical industry to develop consensus recommendations for advancing patient engagement in all stages of clinical pain research in an effective and purposeful manner. This article summarizes the results of this meeting and offers considerations for meaningful and authentic engagement of patient partners in clinical pain research, including recommendations for representation, timing, continuous engagement, measurement, reporting, and research dissemination.

The Use and Perceptions of the Defense and Veterans Pain Rating Scale by Nursing Personnel

BACKGROUND

In 2010, the Office of the US Army Surgeon General recommended the Veterans Administration (VA) assess pain using the Defense and Veterans Pain Rating Scale (DVPRS). One item in the DVPRS is for measuring pain intensity. This item contains a combination of five response metrics: categories, faces, colors, numbers, and functional descriptors. A few studies have supported patients' and health care providers' preferences for the DVPRS and its psychometric properties. However, they also left uncertainties about its usability and validity.

AIMS

To advance our understanding of the DVPRS, this study examined the use and perceptions of the DVPRS' pain intensity item by nursing personnel during multi-modal care.

DESIGN

A cross-sectional survey design was used.

SETTING

VA Community Living Center.

PARTICIPANTS

Nursing personnel.

METHODS

Nursing personnel answered closed- and open-ended survey questions during a single session.

RESULTS

Nursing personnel reported sufficient training before implementing the measure and that patients primarily used the numeric metric. When patients used a non-numeric metric, the nursing personnel responded in variable ways. In addition, the nursing personnel interpreted the functional descriptors differently. The nursing personnel also noted the need to supplement the pain intensity item with patients' pain duration and pain location.

CONCLUSIONS

Results from this study inform the nursing community about the DVPRS' pain intensity item, which combines multiple response metrics. The results support the need for nursing units to generate and standardize procedures for using the item to measure multi-site pain and for interpreting and documenting patients' non-numeric responses. The effects of such procedures on the measure's usability and psychometric properties warrants additional investigation.

Evaluation of intervention components to maximize yoga practice among people with chronic pain taking opioid agonist therapy: A factorial experiment using the multiphase optimization strategy framework

BACKGROUND

Chronic pain affects up to half of individuals taking opioid agonist therapy (OAT; i.e., methadone and buprenorphine) for opioid use disorder (OUD), and yoga-based interventions may be useful for decreasing pain-related disability. Whereas more yoga practice (i.e., higher "dosage") may improve pain-related outcomes, it can be challenging for people with chronic pain taking OAT to attend class regularly and sustain a regular personal yoga practice. Therefore, we plan to optimize a yoga-based intervention (YBI) package in order to support class attendance and personal practice, thus maximizing the yoga dose received.

STUDY DESIGN

Using the Multiphase Optimization Strategy (MOST) framework, we will conduct a factorial experiment to examine four intervention components that may be added to a weekly yoga class as part of a YBI. Components include: 1) personal practice videos featuring study yoga teachers, 2) two private sessions with a yoga teacher, 3) daily text messages to inspire personal practice, and 4) monetary incentives for class attendance. The primary outcome will be minutes per week engaged in yoga (including class attendance and personal practice). We plan to enroll 192 adults with chronic pain who are taking OAT for OUD in this 2x2x2x2 factorial experiment.

CONCLUSION

Results of the study will guide development of an optimized yoga-based intervention package that maximizes dosage of yoga received. The final treatment package can be tested in a multisite efficacy trial of yoga to reduce pain interference in daily functioning in people with chronic pain who are taking OAT.

TRIAL REGISTRATION

Pre-registration of the study was completed on ClinicalTrials.gov (identifier: NCT04641221).

Recommendations for Patient-Reported Outcomes Measurement Information System pediatric measures in youth with chronic pain: a COnsensus-based Standards for the selection of health Measurement INstruments systematic review of measurement properties

ABSTRACT

The Patient-Reported Outcome Measurement Information System (PROMIS) pediatric measures assess physical, emotional, and social health among children and adolescents. However, their measurement properties have not been systematically examined in youth with chronic pain. A systematic review applying the COnsensus based Standards for the selection of health Measurement INstruments (COSMIN) methodology was conducted to evaluate self-reported PROMIS pediatric measures in youth with chronic pain, assessing 8 measurement properties across all versions (item bank, short form, and computer adaptive testing) from 63 studies covering 25 measures. Moderate or high-quality evidence was most available for content validity, structural validity, internal consistency (measurement precision), and construct validity. Four short-form PROMIS pediatric measures-mobility, anxiety, depressive symptoms, and physical stress experiences-achieved recommendation for the use in chronic pain clinical trials; 7 approached recommendation and 14, including the commonly used PROMIS Pediatric Pain Interference Scale, would be recommended with further evidence. Recommendations were also provided for the use of each measure in observational studies. Overall, based on the existing evidence, a total of 11 self-reported PROMIS pediatric short-form measures, including pain intensity, pain behavior, mobility, sleep disturbance, sleep-related impairment, anxiety, depressive symptoms, psychological stress experiences, physical stress experiences, family relationships, and positive effect, are recommended or approaching recommendation for use in youth ages 8 to 19 years with chronic pain. Research is needed to further establish test-retest reliability, measurement errors, cross-cultural validity, and responsiveness. Future work should expand the evaluation of PROMIS pediatric measures in subpopulations of youth with chronic pain, particularly young children and those with neurodevelopmental disabilities.

The effect of lacosamide in peripheral neuropathic pain: A randomized, double-blind, placebo-controlled, phenotype-stratified trial

BACKGROUND

Neuropathic pain is common and difficult to treat. The sodium channel blocker lacosamide is efficacious in animal models of pain, but its effect on neuropathic pain in humans is inconclusive.

METHODS

In a multicentre, randomized, double-blinded placebo-controlled phenotype stratified trial, we examined if lacosamide produced better pain relief in patients with the irritable nociceptor phenotype compared to those without. The primary outcome was the change in daily average pain from baseline to last week of 12 weeks of treatment. Secondary and tertiary outcomes included pain relief, patient global impression of change and presence of 30% and 50% pain reduction.

RESULTS

The study was prematurely closed with 93 patients included and 63 randomized to lacosamide or placebo in a 2:1 ratio, of which 49 fulfilled the per protocol criteria and was used for the primary objective. We did not find a better effect of lacosamide in patients with the irritable nociceptor phenotype, the 95% CI for the primary objective was 0.41 (-1.2 to 2.0). For all patients randomized, lacosamide had no effect on the primary outcome, but significantly more patients were responders to lacosamide than during placebo, with an NNT of 4.0 (95% CI 2.3-16.1) and 5.0 (95% CI 2.8-24.5) for 30% and 50% pain reduction respectively. We did not identify any predictors for response. Lacosamide was generally well tolerated.

CONCLUSION

We could not confirm that lacosamide was more efficacious in patients with the irritable nociceptor type, but the study was prematurely closed, so we cannot exclude a small difference.

SIGNIFICANCE

Treatment of neuropathic pain is often a trial and error process. Little is known about which patient benefit from which kind of medication. The sodium channel blocker lacosamide shows variable effect on neuropathic pain. Pain sensory phenotype, as defined by quantitative sensory testing, did not predict response to treatment with lacosamide.

Placebo and nocebo responses in painful diabetic neuropathy: systematic review and meta-analysis

ABSTRACT

This preregistered (CRD42021223379) systematic review and meta-analysis aimed to characterize the placebo and nocebo responses in placebo-controlled randomized clinical trials (RCTs) on painful diabetic neuropathy (PDN), updating the previous literature by a decade. Four databases were searched for PDN trials published in the past 20 years, testing oral medications, adopting a parallel-group design. Magnitude of placebo or nocebo responses, Cochrane risk of bias, heterogeneity, and moderators were evaluated. Searches identified 21 studies (2425 placebo-treated patients). The overall mean pooled placebo response was -1.54 change in the pain intensity from baseline [95% confidence interval (CI): -1.52, -1.56, I 2 = 72], with a moderate effect size (Cohen d = 0.72). The pooled placebo 50% response rate was 25% [95% CI: 22, 29, I 2 = 50%]. The overall percentage of patients with adverse events (AEs) in the placebo arms was 53.3% [95% CI: 50.9, 55.7], with 5.1% [95% CI: 4.2, 6] of patients dropping out due to AEs. The year of study initiation was the only significant moderator of placebo response (regression coefficient = -0.06, [95% CI: -0.10, -0.02, P = 0.007]). More recent RCTs tended to be longer, bigger, and to include older patients (N = 21, rs = 0.455, P = 0.038, rs = 0.600, P = 0.004, rs = 0.472, P = 0.031, respectively). Our findings confirm the magnitude of placebo and nocebo responses, identify the year of study initiation as the only significant moderator of placebo response, draw attention to contextual factors such as confidence in PDN treatments, patients' previous negative experiences, intervention duration, and information provided to patients before enrollment.

Digital and precision clinical trials: innovations for testing mental health medications, devices, and psychosocial treatments

Mental health treatment advances - including neuropsychiatric medications and devices, psychotherapies, and cognitive treatments - lag behind other fields of clinical medicine such as cardiovascular care. One reason for this gap is the traditional techniques used in mental health clinical trials, which slow the pace of progress, produce inequities in care, and undermine precision medicine goals. Newer techniques and methodologies, which we term digital and precision trials, offer solutions. These techniques consist of (1) decentralized (i.e., fully-remote) trials which improve the speed and quality of clinical trials and increase equity of access to research, (2) precision measurement which improves success rate and is essential for precision medicine, and (3) digital interventions, which offer increased reach of, and equity of access to, evidence-based treatments. These techniques and their rationales are described in detail, along with challenges and solutions for their utilization. We conclude with a vignette of a depression clinical trial using these techniques.

Transcutaneous electrical acupoint stimulation for cancer-related pain management in patients receiving chronic opioid therapy: a randomized clinical trial

PURPOSE

The opioid crisis resulting from its use disorder and overdose poses additional challenges for cancer pain management. The American Society of Clinical Oncology Practice Guideline recommends acupuncture therapy for the management of adult cancer-related pain (CRP), but the effectiveness of transcutaneous electrical acupoint stimulation (TEAS) on CRP remains uncertain.

METHODS

This 5-week prospective randomized clinical trial was conducted at 2 hospitals in China, and participants with CRP receiving chronic opioid therapy were randomized 1:1 into two groups between December 2014 and June 2018. The true TEAS group underwent 15 sessions of TEAS treatments over 3 consecutive weeks, while the control group received sham stimulation. The primary outcome was the numerical rating scale (NRS) score in the past 24h at week 3. The secondary outcomes included morphine equivalent daily dose, quality of life and adverse events.

RESULTS

A total of 159 participants were included in the modified intention-to-treat population. The baseline characteristics were similar in both groups. The mean NRS scores were 0.98 points at week 3 in the true TEAS group and 1.41 points in the sham group, with the mean difference between groups of -0.43 points (P < 0.001; OR = 0.68, P < 0.05). The proportion of patients with NRS reduction more than thirty percentage at week 3 was 50.00% in the true TEAS group and 35.44% in the sham group (RD = 0.15, P > 0.05; RR = 1.41, P > 0.05). No significant difference in pain intensity between the two groups was observed during the follow-up period without TEAS intervention (week 4, OR = 0.83, P > 0.05; week 5, OR = 0.83, P > 0.05). The Karnofsky Performance Status value suggested that patients in the true TEAS group experienced an improved quality of life (Between-group differences: week 3, 3.5%, P < 0.05; week 4, 4.6%, P < 0.001; week 5, 5.6%, P < 0.001).

CONCLUSIONS

The 3-week application of TEAS in patients with CRP receiving chronic opioid therapy resulted in a statistically significant reduction in pain scores, but the observed reduction was of uncertain clinical significance. The prolonged analgesic effect of TEAS was not confirmed in this trial.

CLINICALTRIAL

GOV: ChiCTR-TRC-13003803.

Impact of chronic pelvic pain and painful bladder syndrome on the Pittsburgh Sleep Quality Index on women with deep endometriosis: a cross-sectional study

INTRODUCTION AND HYPOTHESIS

Painful bladder syndrome (PBS) is frequently associated with deep endometriosis (DE), and both conditions cause chronic pelvic pain (CPP), which often impairs sleep quality. This study was aimed at analyzing the impact of CPP plus PBS in women with DE on the global sleep quality index using the Pittsburgh Sleep Quality Index (PSQI) and subsequently examine each sleep dimension.

METHODS

One hundred and forty women with DE were included and answered the PSQI and the O'Leary-Sant Interstitial Cystitis Symptoms and Problem Index questionnaires with or without CPP. Women were categorized into good or poor sleepers using the PSQI cutoff; subsequently, a linear regression model was used to analyze the PSQI score and a logistic regression model for each questionnaire's sleep component.

RESULTS

Only 13% of women with DE had a good sleep. Approximately 20% of those with DE but no/mild pain were good sleepers; 138 women with DE (88.5%), 94% with PBS, and 90.5% with moderate/severe pain were poor sleepers. For PSQI components, CPP worsened the subjective sleep quality by more than threefold (p = 0.019), increased sleep disturbances by nearly sixfold (p = 0.03), and decreased the sleep duration by practically sevenfold (p = 0.019). Furthermore, PBS increased sleep disturbances by nearly fivefold (p < 0.01).

CONCLUSIONS

The addition of PBS to CPP in women with DE is devastating for overall sleep quality, probably because it impacts some sleep dimensions unaffected by CPP and amplifies the problem in those already affected by pain.

Covariate Adjustment in Chronic Pain Trials: An Oft-Missed Opportunity

Self-reported pain intensity, frequently used as an outcome in randomized clinical trials (RCTs) of chronic pain, is often highly variable and could be associated with multiple baseline factors. Thus, the assay sensitivity of pain trials (ie, the ability of the trial to detect a true treatment effect) could be improved by including prespecified baseline factors in the primary statistical model. The objective of this focus article was to characterize the baseline factors included in statistical analyses of chronic pain RCTs. Seventy-three RCTs published between 2016 and 2021 that investigated interventions for chronic pain were included. The majority of trials identified a single primary analysis (72.6%; n = 53). Of these, 60.4% (n = 32) included one or more covariates in the primary statistical model, most commonly baseline value of the primary outcome, study site, sex, and age. Only one of the trials reported information regarding associations between covariates and outcomes (ie, information that could inform prioritization of covariates for prespecification in future analyses). These findings demonstrate inconsistent use of covariates in the statistical models in chronic pain clinical trials. Prespecified adjustments for baseline covariates that could increase precision and assay sensitivity should be considered in future clinical trials of chronic pain treatments. PERSPECTIVE: This review demonstrates inconsistent inclusion and potential underutilization of covariate adjustment in analyses of chronic pain RCTs. This article highlights areas for possible improvement in design and reporting related to covariate adjustment to improve efficiency in future RCTs.

Research objectives and general considerations for pragmatic clinical trials of pain treatments: IMMPACT statement

ABSTRACT

Many questions regarding the clinical management of people experiencing pain and related health policy decision-making may best be answered by pragmatic controlled trials. To generate clinically relevant and widely applicable findings, such trials aim to reproduce elements of routine clinical care or are embedded within clinical workflows. In contrast with traditional efficacy trials, pragmatic trials are intended to address a broader set of external validity questions critical for stakeholders (clinicians, healthcare leaders, policymakers, insurers, and patients) in considering the adoption and use of evidence-based treatments in daily clinical care. This article summarizes methodological considerations for pragmatic trials, mainly concerning methods of fundamental importance to the internal validity of trials. The relationship between these methods and common pragmatic trials methods and goals is considered, recognizing that the resulting trial designs are highly dependent on the specific research question under investigation. The basis of this statement was an Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) systematic review of methods and a consensus meeting. The meeting was organized by the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION) public-private partnership. The consensus process was informed by expert presentations, panel and consensus discussions, and a preparatory systematic review. In the context of pragmatic trials of pain treatments, we present fundamental considerations for the planning phase of pragmatic trials, including the specification of trial objectives, the selection of adequate designs, and methods to enhance internal validity while maintaining the ability to answer pragmatic research questions.

The relationship between pain intensity and insomnia in women with deep endometriosis, a cross-sectional study

PURPOSE

To investigate the relationship between pain intensity and insomnia frequency in women with a diagnosis of deep endometriosis. The hypothesis is that these patients with moderate or severe pain have a higher frequency of insomnia than those with mild or no pain.

METHODS

We conducted a cross-sectional study of women with deep endometriosis categorized by pelvic pain intensity based on a numerical scale. Insomnia was assessed through a self-reported questionnaire, and multiple logistic regression was used to control for confounders between pain and insomnia.

RESULTS

We included 234 women in the study, 39 (17%) without pelvic pain; 66 (29%) with mild pain; 53 (23%) moderate pain; and 76 (32%) severe pain. Twenty-nine (74%) pain-free women and 50 (75%) with mild pain had no insomnia; only 3 (8%) of the former and 3 (4%) of the latter group had severe insomnia. However, twenty-nine (55%) women with moderate pain and 37 (48%) with severe pain had insomnia. The logistic regression model showed that moderate to severe pain increased insomnia 2.8 times, twice for every 10 years of pain duration, and twice in women with low education levels.

CONCLUSIONS

Women with moderate or severe pain had a high frequency of insomnia, increasing management complexity in patients with deep endometriosis. Pain intensity, pain duration, and low education level increased the chance of insomnia in those patients.

Predicting Treatment Responses in Patients With Osteoarthritis: Results From Two Phase III Tanezumab Randomized Clinical Trials

Prediction of treatment responses is essential to move forward translational science. Our question was to identify patient-based variables that predicted responses to treatments. We conducted secondary analyses on pooled data from two randomized phase III clinical trials (NCT02697773 and NCT02709486) conducted in participants with moderate to severe osteoarthritis randomized to subcutaneous placebo (n = 514) or tanezumab 2.5 mg (n = 514). We used gradient boosted regression trees to identify variables that predicted Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain subscale scores at Week 16 and marginal plots to determine the directional relationship between each variable category and responses to placebo or tanezumab within the models. We also used Virtual Twins models to identify potential subgroups of response to the active treatment vs. placebo. We found that responses to placebo were predicted by baseline WOMAC Physical Function, baseline WOMAC Pain, the radiographic classification of the index joint, and the standard deviation of diary pain scores at baseline. In contrast, baseline WOMAC Pain along with failure of prior medications, duration of disease, and standard deviation of diary pain scores at baseline were predictive of tanezumab responses as expressed by the WOMAC Pain scores at Week 16. Those who responded to tanezumab vs. placebo were identified based on the radiographic classification of the index joint and either age or smoking status. These secondary-data analyses identified distinct and common patient-based variables to predict response to placebo or tanezumab. These findings will inform the design of future clinical trials, helping to move forward clinical pharmacology and translational science.

Expectations for Improvement: A Neglected but Potentially Important Covariate or Moderator for Chronic Pain Clinical Trials

Variability in pain-related outcomes can hamper assay sensitivity of chronic pain clinical trials. Expectations of outcome in such trials may account for some of this variability, and thereby impede development of novel pain treatments. Measurement of participants' expectations prior to initiating study treatment (active or placebo) is infrequent, variable, and often unvalidated. Efforts to optimize and standardize measurement, analysis, and management of expectations are needed. In this Focus Article, we provide an overview of research findings on the relationship between baseline expectations and pain-related outcomes in clinical trials of pharmacological and nonpharmacological pain treatments. We highlight the potential benefit of adjusting for participants' expectations in clinical trial analyses and draw on findings from patient interviews to discuss critical issues related to measurement of expectations. We conclude with suggestions regarding future studies focused on better understanding the utility of incorporating these measures into clinical trial analyses. PERSPECTIVE: This focus article provides an overview of the relationship between participants' baseline expectations and pain-related outcomes in the setting of clinical trials of chronic pain treatments. Systematic research focused on the measurement of expectations and the impact of adjusting for expectations in clinical trial analyses may improve assay sensitivity.

Mirogabalin for Central Neuropathic Pain After Spinal Cord Injury: A Randomized, Double-Blind, Placebo-Controlled, Phase 3 Study in Asia

BACKGROUND AND OBJECTIVES

Patients with spinal cord injury (SCI) commonly experience central neuropathic pain (CNeP), which is challenging to treat. Mirogabalin is effective for peripheral neuropathic pain, but evidence for CNeP is lacking.

METHODS

This randomized, double-blind, placebo-controlled, phase 3 study investigated mirogabalin efficacy and safety for the treatment of CNeP in patients with traumatic SCI. Adult patients from 120 sites throughout Japan, Korea, and Taiwan were randomized (1:1) to receive placebo or mirogabalin (5 mg twice daily [BID] for 1 week, 10 mg BID for 1 week, and 10 or 15 mg BID for 12 weeks). Patients with moderate renal impairment received half the dosage. The primary efficacy endpoint was change from baseline in the weekly average daily pain score (ADPS) at week 14. The secondary endpoints included ADPS responder rates, the Short-Form McGill Pain Questionnaire (SF-MPQ), average daily sleep interference score (ADSIS), and Neuropathic Pain Symptom Inventory (NPSI). Adverse events were monitored for safety.

RESULTS

Each treatment group comprised 150 patients. Mirogabalin elicited a statistical and clinically relevant improvement in change from baseline in the weekly ADPS at week 14 (least-squares mean difference [95% CI] vs placebo -0.71 [-1.08 to -0.34], p = 0.0001). Responder rates at week 14 were higher for mirogabalin than those for placebo (odds ratio [95% CI] 1.91 [1.11-3.27] for the ≥30% responder rate; 2.52 [1.11-5.71] for the ≥50% responder rate). Statistical improvements (i.e., least-squares mean difference [95% CI] vs placebo) were also observed in the SF-MPQ (-2.4 [-3.8 to -1.1]), ADSIS -0.71 (-1.04 to -0.38), and NPSI -7.7 (-11.1 to -4.4) scores. Most treatment-emergent adverse events were mild; no serious adverse drug reactions were reported.

DISCUSSION

Mirogabalin elicited clinically relevant decreases in pain and was well tolerated, suggesting that mirogabalin is a promising treatment for patients with CNeP due to SCI.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov (NCT03901352); first submitted April 3, 2019; first patient enrolled March 14, 2019; available at clinicaltrials.gov/ct2/show/NCT03901352.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that in adult patients with CNeP due to traumatic SCI, mirogabalin, 10 or 15 mg BID, effectively improves weekly ADPS at week 14.

Blinding and sham control methods in trials of physical, psychological, and self-management interventions for pain (article I): a systematic review and description of methods

ABSTRACT

Blinding is challenging in randomised controlled trials of physical, psychological, and self-management therapies for pain, mainly because of their complex and participatory nature. To develop standards for the design, implementation, and reporting of control interventions in efficacy and mechanistic trials, a systematic overview of currently used sham interventions and other blinding methods was required. Twelve databases were searched for placebo or sham-controlled randomised clinical trials of physical, psychological, and self-management treatments in a clinical pain population. Screening and data extraction were performed in duplicate, and trial features, description of control methods, and their similarity to the active intervention under investigation were extracted (protocol registration ID: CRD42020206590). The review included 198 unique control interventions, published between 2008 and December 2021. Most trials studied people with chronic pain, and more than half were manual therapy trials. The described control interventions ranged from clearly modelled based on the active treatment to largely dissimilar control interventions. Similarity between control and active interventions was more frequent for certain aspects (eg, duration and frequency of treatments) than others (eg, physical treatment procedures and patient sensory experiences). We also provide an overview of additional, potentially useful methods to enhance blinding, as well as the reporting of processes involved in developing control interventions. A comprehensive picture of prevalent blinding methods is provided, including a detailed assessment of the resemblance between active and control interventions. These findings can inform future developments of control interventions in efficacy and mechanistic trials and best-practice recommendations.

Widespread Pain Phenotypes Impact Treatment Efficacy Results in Randomized Clinical Trials for Interstitial Cystitis/Bladder Pain Syndrome: A MAPP Network Study

Clinical trials of pain are notoriously difficult and inefficient in demonstrating efficacy even for known efficacious treatments. Determining the appropriate pain phenotype to study can be problematic. Recent work has identified the extend of widespread pain as an important factor in the likelihood of response to therapy, but has not been tested in clinical trials. Using data from three previously published negative studies of the treatment of interstitial cystitis/ bladder pain with data on the extent of widespread pain, we examined the response of patients to different therapies base on the amount of pain beyond the pelvis. Participants with predominately local but not widespread pain responded to therapy targeting local symptoms. Participants with widespread and local pain responded to therapy targeting widespread pain. Differentiating patients with and without widespread pain phenotypes may be a key feature of designing future pain clinical trials to demonstrate treatments that are effective versus not.

Optimizing and Accelerating the Development of Precision Pain Treatments for Chronic Pain: IMMPACT Review and Recommendations

Large variability in the individual response to even the most-efficacious pain treatments is observed clinically, which has led to calls for a more personalized, tailored approach to treating patients with pain (ie, "precision pain medicine"). Precision pain medicine, currently an aspirational goal, would consist of empirically based algorithms that determine the optimal treatments, or treatment combinations, for specific patients (ie, targeting the right treatment, in the right dose, to the right patient, at the right time). Answering this question of "what works for whom" will certainly improve the clinical care of patients with pain. It may also support the success of novel drug development in pain, making it easier to identify novel treatments that work for certain patients and more accurately identify the magnitude of the treatment effect for those subgroups. Significant preliminary work has been done in this area, and analgesic trials are beginning to utilize precision pain medicine approaches such as stratified allocation on the basis of prespecified patient phenotypes using assessment methodologies such as quantitative sensory testing. Current major challenges within the field include: 1) identifying optimal measurement approaches to assessing patient characteristics that are most robustly and consistently predictive of inter-patient variation in specific analgesic treatment outcomes, 2) designing clinical trials that can identify treatment-by-phenotype interactions, and 3) selecting the most promising therapeutics to be tested in this way. This review surveys the current state of precision pain medicine, with a focus on drug treatments (which have been most-studied in a precision pain medicine context). It further presents a set of evidence-based recommendations for accelerating the application of precision pain methods in chronic pain research. PERSPECTIVE: Given the considerable variability in treatment outcomes for chronic pain, progress in precision pain treatment is critical for the field. An array of phenotypes and mechanisms contribute to chronic pain; this review summarizes current knowledge regarding which treatments are most effective for patients with specific biopsychosocial characteristics.

Optimal pharmacotherapy pathway in adults with diabetic peripheral neuropathic pain: the OPTION-DM RCT

BACKGROUND

The mainstay of treatment for diabetic peripheral neuropathic pain is pharmacotherapy, but the current National Institute for Health and Care Excellence guideline is not based on robust evidence, as the treatments and their combinations have not been directly compared.

OBJECTIVES

To determine the most clinically beneficial, cost-effective and tolerated treatment pathway for diabetic peripheral neuropathic pain.

DESIGN

A randomised crossover trial with health economic analysis.

SETTING

Twenty-one secondary care centres in the UK.

PARTICIPANTS

Adults with diabetic peripheral neuropathic pain with a 7-day average self-rated pain score of ≥ 4 points (Numeric Rating Scale 0-10).

INTERVENTIONS

Participants were randomised to three commonly used treatment pathways: (1) amitriptyline supplemented with pregabalin, (2) duloxetine supplemented with pregabalin and (3) pregabalin supplemented with amitriptyline. Participants and research teams were blinded to treatment allocation, using over-encapsulated capsules and matching placebos. Site pharmacists were unblinded.

OUTCOMES

The primary outcome was the difference in 7-day average 24-hour Numeric Rating Scale score between pathways, measured during the final week of each pathway. Secondary end points included 7-day average daily Numeric Rating Scale pain score at week 6 between monotherapies, quality of life (Short Form questionnaire-36 items), Hospital Anxiety and Depression Scale score, the proportion of patients achieving 30% and 50% pain reduction, Brief Pain Inventory - Modified Short Form items scores, Insomnia Severity Index score, Neuropathic Pain Symptom Inventory score, tolerability (scale 0-10), Patient Global Impression of Change score at week 16 and patients' preferred treatment pathway at week 50. Adverse events and serious adverse events were recorded. A within-trial cost-utility analysis was carried out to compare treatment pathways using incremental costs per quality-adjusted life-years from an NHS and social care perspective.

RESULTS

A total of 140 participants were randomised from 13 UK centres, 130 of whom were included in the analyses. Pain score at week 16 was similar between the arms, with a mean difference of -0.1 points (98.3% confidence interval -0.5 to 0.3 points) for duloxetine supplemented with pregabalin compared with amitriptyline supplemented with pregabalin, a mean difference of -0.1 points (98.3% confidence interval -0.5 to 0.3 points) for pregabalin supplemented with amitriptyline compared with amitriptyline supplemented with pregabalin and a mean difference of 0.0 points (98.3% confidence interval -0.4 to 0.4 points) for pregabalin supplemented with amitriptyline compared with duloxetine supplemented with pregabalin. Results for tolerability, discontinuation and quality of life were similar. The adverse events were predictable for each drug. Combination therapy (weeks 6-16) was associated with a further reduction in Numeric Rating Scale pain score (mean 1.0 points, 98.3% confidence interval 0.6 to 1.3 points) compared with those who remained on monotherapy (mean 0.2 points, 98.3% confidence interval -0.1 to 0.5 points). The pregabalin supplemented with amitriptyline pathway had the fewest monotherapy discontinuations due to treatment-emergent adverse events and was most commonly preferred (most commonly preferred by participants: amitriptyline supplemented with pregabalin, 24%; duloxetine supplemented with pregabalin, 33%; pregabalin supplemented with amitriptyline, 43%; p = 0.26). No single pathway was superior in cost-effectiveness. The incremental gains in quality-adjusted life-years were small for each pathway comparison [amitriptyline supplemented with pregabalin compared with duloxetine supplemented with pregabalin -0.002 (95% confidence interval -0.011 to 0.007) quality-adjusted life-years, amitriptyline supplemented with pregabalin compared with pregabalin supplemented with amitriptyline -0.006 (95% confidence interval -0.002 to 0.014) quality-adjusted life-years and duloxetine supplemented with pregabalin compared with pregabalin supplemented with amitriptyline 0.007 (95% confidence interval 0.0002 to 0.015) quality-adjusted life-years] and incremental costs over 16 weeks were similar [amitriptyline supplemented with pregabalin compared with duloxetine supplemented with pregabalin -£113 (95% confidence interval -£381 to £90), amitriptyline supplemented with pregabalin compared with pregabalin supplemented with amitriptyline £155 (95% confidence interval -£37 to £625) and duloxetine supplemented with pregabalin compared with pregabalin supplemented with amitriptyline £141 (95% confidence interval -£13 to £398)].

LIMITATIONS

Although there was no placebo arm, there is strong evidence for the use of each study medication from randomised placebo-controlled trials. The addition of a placebo arm would have increased the duration of this already long and demanding trial and it was not felt to be ethically justifiable.

FUTURE WORK

Future research should explore (1) variations in diabetic peripheral neuropathic pain management at the practice level, (2) how OPTION-DM (Optimal Pathway for TreatIng neurOpathic paiN in Diabetes Mellitus) trial findings can be best implemented, (3) why some patients respond to a particular drug and others do not and (4) what options there are for further treatments for those patients on combination treatment with inadequate pain relief.

CONCLUSIONS

The three treatment pathways appear to give comparable patient outcomes at similar costs, suggesting that the optimal treatment may depend on patients' preference in terms of side effects.

TRIAL REGISTRATION

The trial is registered as ISRCTN17545443 and EudraCT 2016-003146-89.

FUNDING

This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme, and will be published in full in Health Technology Assessment; Vol. 26, No. 39. See the NIHR Journals Library website for further project information.

An Update On Proficiency of Voltage-gated Ion Channel Blockers in the Treatment of Inflammation-associated Diseases

Inflammation is the body's mechanism to trigger the immune system, thereby preventing bacteria and viruses from manifesting their toxic effect. Inflammation plays a vital role in regulating inflammatory mediator levels to initiate the wound healing process depending on the nature of the stimuli. This process occurs due to chemical release from white blood cells by elevating blood flow to the site of action, leading to redness and increased body temperature. Currently, there are numerous Non-steroidal anti-inflammatory drugs (NSAIDs) available, but these drugs are reported with adverse effects such as gastric bleeding, progressive kidney damage, and increased risk of heart attacks when prolonged use. For such instances, alternative options need to be adopted. The introduction of voltage-gated ion channel blockers can be a substantial alternative to mask the side effects of these currently available drugs. Chronic inflammatory disorders such as rheumatoid and osteoarthritis, cancer and migraine, etc., can cause dreadful pain, which is often debilitating for the patient. The underlying mechanism for both acute and chronic inflammation involves various complex receptors, different types of cells, receptors, and proteins. The working of voltage-gated sodium and calcium channels is closely linked to both inflammatory and neuropathic pain. Certain drugs such as carbamazepine and gabapentin, which are ion channel blockers, have greater pharmacotherapeutic activity for sodium and calcium channel blockers for the treatment of chronic inflammatory pain states. This review intends to provide brief information on the mechanism of action, latest clinical trials, and applications of these blockers in treating inflammatory conditions.

The Effects of Combined Respiratory-Gated Auricular Vagal Afferent Nerve Stimulation and Mindfulness Meditation for Chronic Low Back Pain: A Pilot Study

OBJECTIVE

Respiratory-gated Auricular Vagal Afferent Nerve stimulation (RAVANS) is a safe nonpharmacological approach to managing chronic pain. The purpose of the current study was to examine (1) the feasibility and acceptability of RAVANS, combined with mindful meditation (MM) for chronic low back pain (CLBP), (2) the potential synergy of MM+RAVANS on improving pain, and (3) possible moderators of the influence of MM+RAVANS on pain.

DESIGN

Pilot feasibility and acceptability study.

SETTING

Pain management center at large academic medical center.

SUBJECTS

Nineteen adults with CLBP and previous MM training.

METHODS

Participants attended two sessions during which they completed quantitative sensory testing (QST), rated pain severity, and completed a MM+stimulation session. Participants received RAVANS during one visit and sham stimulation during the other, randomized in order. Following intervention, participants repeated QST.

RESULTS

MM+RAVANS was well tolerated, acceptable, and feasible to provide relief for CLBP. Both MM+stimulation sessions resulted in improved back pain severity, punctate pain ratings, and pressure pain threshold. Individuals with greater negative affect showed greater back pain improvement from MM+RAVANS while those with greater mindfulness showed greater back pain improvement from MM+sham.

CONCLUSIONS

Results suggest that for CLBP patients with prior MM training, the analgesic effects of MM may have overshadowed effects of RAVANS given the brief single session MM+RAVANS intervention. However, those with greater negative affect may benefit from combined MM+RAVANS.

Comparison of amitriptyline supplemented with pregabalin, pregabalin supplemented with amitriptyline, and duloxetine supplemented with pregabalin for the treatment of diabetic peripheral neuropathic pain (OPTION-DM): a multicentre, double-blind, randomised crossover trial

BACKGROUND

Diabetic peripheral neuropathic pain (DPNP) is common and often distressing. Most guidelines recommend amitriptyline, duloxetine, pregabalin, or gabapentin as initial analgesic treatment for DPNP, but there is little comparative evidence on which one is best or whether they should be combined. We aimed to assess the efficacy and tolerability of different combinations of first-line drugs for treatment of DPNP.

METHODS

OPTION-DM was a multicentre, randomised, double-blind, crossover trial in patients with DPNP with mean daily pain numerical rating scale (NRS) of 4 or higher (scale is 0-10) from 13 UK centres. Participants were randomly assigned (1:1:1:1:1:1), with a predetermined randomisation schedule stratified by site using permuted blocks of size six or 12, to receive one of six ordered sequences of the three treatment pathways: amitriptyline supplemented with pregabalin (A-P), pregabalin supplemented with amitriptyline (P-A), and duloxetine supplemented with pregabalin (D-P), each pathway lasting 16 weeks. Monotherapy was given for 6 weeks and was supplemented with the combination medication if there was suboptimal pain relief (NRS >3), reflecting current clinical practice. Both treatments were titrated towards maximum tolerated dose (75 mg per day for amitriptyline, 120 mg per day for duloxetine, and 600 mg per day for pregabalin). The primary outcome was the difference in 7-day average daily pain during the final week of each pathway. This trial is registered with ISRCTN, ISRCTN17545443.

FINDINGS

Between Nov 14, 2017, and July 29, 2019, 252 patients were screened, 140 patients were randomly assigned, and 130 started a treatment pathway (with 84 completing at least two pathways) and were analysed for the primary outcome. The 7-day average NRS scores at week 16 decreased from a mean 6·6 (SD 1·5) at baseline to 3·3 (1·8) at week 16 in all three pathways. The mean difference was -0·1 (98·3% CI -0·5 to 0·3) for D-P versus A-P, -0·1 (-0·5 to 0·3) for P-A versus A-P, and 0·0 (-0·4 to 0·4) for P-A versus D-P, and thus not significant. Mean NRS reduction in patients on combination therapy was greater than in those who remained on monotherapy (1·0 [SD 1·3] vs 0·2 [1·5]). Adverse events were predictable for the monotherapies: we observed a significant increase in dizziness in the P-A pathway, nausea in the D-P pathway, and dry mouth in the A-P pathway.

INTERPRETATION

To our knowledge, this was the largest and longest ever, head-to-head, crossover neuropathic pain trial. We showed that all three treatment pathways and monotherapies had similar analgesic efficacy. Combination treatment was well tolerated and led to improved pain relief in patients with suboptimal pain control with a monotherapy.

FUNDING

National Institute for Health Research (NIHR) Health Technology Assessment programme.

Clinical Trials in Pancreatitis: Opportunities and Challenges in the Design and Conduct of Patient-Focused Clinical Trials in Recurrent Acute and Chronic Pancreatitis: Summary of a National Institute of Diabetes and Digestive and Kidney Diseases Workshop

ABSTRACT

Recurrent acute pancreatitis and chronic pancreatitis represent high morbidity diseases, which are frequently associated with chronic abdominal pain, pancreatic insufficiencies, and reduced quality of life. Currently, there are no therapies to reverse or delay disease progression, and clinical trials are needed to investigate potential interventions that would address this important gap. This conference report provides details regarding information shared during a National Institute of Diabetes and Digestive and Kidney Diseases-sponsored workshop on Clinical Trials in Pancreatitis that sought to clearly delineate the current gaps and opportunities related to the design and conduct of patient-focused trials in recurrent acute pancreatitis and chronic pancreatitis. Key stakeholders including representatives from patient advocacy organizations, physician investigators (including clinical trialists), the US Food and Drug Administration, and the National Institutes of Health convened to discuss challenges and opportunities with particular emphasis on lessons learned from trials in participants with other painful conditions, as well as the value of incorporating the patient perspective throughout all stages of trials.

Efficacy of donepezil for the treatment of oxaliplatin-induced peripheral neuropathy: DONEPEZOX, a protocol of a proof of concept, randomised, triple-blinded and multicentre trial

BACKGROUND

The use of oxaliplatin in digestive tract cancers could induce severe peripheral neuropathy (OIPN) decreasing the quality of life of patients and survivors. There is currently, no univocal treatment for these peripheral neuropathies. Donepezil, a reversible inhibitor of cholinesterase, used to treat Alzheimer's disease and dementia, is reported to have a good safety profile in humans, and preclinical data have provided initial evidence of its effectiveness in diminishing neuropathic symptoms and related comorbidities in OIPN animal models.

METHODS

The DONEPEZOX trial will be a proof-of-concept, randomised, triple-blinded, and multicentre study. It will be the first clinical trial evaluating the efficacy and safety of donepezil for the management of OIPN. Adult cancer survivors with OIPN that report sensory neuropathy according to QLQ-CIPN20 sensory score (equivalence of a grade ≥ 2), at least 6 months after the end of an oxaliplatin-based chemotherapy will be included. Eighty patients will be randomly assigned to receive either donepezil or placebo over 16 weeks of treatment. The primary endpoint will be the rate of responders (neuropathic grade decreases according to the QLQ-CIPN20 sensory score) in the donepezil arm. The severity of OIPN will be assessed by the QLQ-CIPN20 sensory scale before and after 16 weeks of treatment. The comparison versus the placebo arm will be a secondary objective. The other secondary endpoints will be tolerance to donepezil, the severity and features of OIPN in each arm before and after treatment, related-comorbidities and quality of life. Fleming's one-stage design will be used for sample size estimation. This design yields a type I error rate of 0.0417 and power of 91% for a responder rate of at least 30% in donepezil arm. A total of 80 randomized patients is planned.

DISCUSSION

This study will allow, in the case of positive results, to initiate a phase 3 randomized and placebo-controlled (primary endpoint) clinical study to assess the therapeutic interest of donepezil to treat OIPN.

TRIAL REGISTRATION

NCT05254639 , clincialtrials.gov, Registered 24 February 2022.

NRD.E1, an innovative non‐opioid therapy for painful diabetic peripheral neuropathy ‐ a randomised proof of concept study

Background

Painful diabetic peripheral neuropathy (PDPN) affects up to 26% of patients with diabetes mellitus, with major impacts on their general health and well‐being. Most available drugs fail to deliver acceptable pain reduction in the majority of patients and are often poorly tolerated. NRD.E1 is a novel product that has shown anti‐nociceptive preclinical effects and good tolerability in healthy volunteer studies.

Methods

This phase 2a, randomized, dose‐finding, Proof of Concept study enrolled patients with PDPN of ≥3 months duration. After at least one treatment‐free week (WO week), 88 patients entered a 1‐week single‐blind (SB)‐placebo run‐in period, followed by 3 weeks' double‐blind (DB) treatment, during which they received NRD.E1 at 10, 40 or 150 mg/day or placebo.

Results

The primary endpoint (change from SB‐placebo run‐in week to week 3 in weekly mean of daily average numerical rating scale [NRS] pain intensity) showed clinically relevant placebo‐corrected treatment effect pain reductions at 40 mg and 150 mg/day of 0.82 (95% CI: 0.07, 1.58, p = 0.034) and 0.66 (95% CI: −0.03, 1.35; p = 0.061) NRS points, respectively, though did not meet the pre‐specified value of p = 0.016 required due to multiplicity. An additional post hoc endpoint looking at the change from WO baseline to week 3 in weekly mean of daily average NRS showed the placebo‐corrected treatment effect was 1.46 (95% CI: 0.26, 2.66), and 1.20 (95% CI: 0.10, 2.29) NRS points, respectively. Secondary and post hoc analyses of NRS pain data (including 30 & 50% responder rate and NNT), sleep interference, Short‐form McGill pain questionnaire (especially pain intensity assessed on Visual Analogue Scale), Patient's and Clinician's Global Impression of Change showed effects consistent with the primary findings. NRD.E1 was well tolerated, with only headache reported in more than two patients and more frequently on NRD.E1 than placebo.

Conclusions

The data suggest that NRD.E1 potentially represents a novel non‐opioid therapeutic option for patients with PDPN, with at least similar efficacy and better tolerability than available therapies, justifying its further evaluation in larger‐scale confirmatory studies.

Significance

NRD.E1 is a novel non‐opioid therapeutic which is being developed for the treatment of PDPN. In this randomized, controlled, dose‐finding, Proof of Concept study, NRD.E1 induced a clinically relevant pain reduction and it was well tolerated. Available data suggest that NRD.E1 has at least similar efficacy and better tolerability than the currently available therapies, potentially offering a promising new therapeutic option to patients with PDPN and possibly other neuropathic pain indications.

Greater baseline pain inclusion criteria in clinical trials increase regression to the mean effect: a modelling study

ABSTRACT

We modelled the effects of pain intensity inclusion thresholds (3/10, 4/10, and 5/10 on a 0- to 10-point numerical pain rating scale) on the magnitude of the regression to the mean effect under conditions that were consistent with the sample mean and variance, and intermeasurement correlation observed in clinical trials for the management of chronic pain. All data were modelled on a hypothetical placebo control group. We found a progressive increase in the mean pain intensity as the pain inclusion threshold increased, but this increase was not uniform, having an increasing effect on baseline measurements compared with study endpoint measurements as the threshold was increased. That is, the regression to the mean effect was magnified by increasing inclusion thresholds. Furthermore, the effect increasing pain inclusion thresholds had on the regression to the mean effect was increased by decreasing sample mean values at baseline and intermeasurement correlations, and increasing sample variance. At its smallest, the regression to the mean effect was 0.13/10 (95% confidence interval: 0.03/10-0.24/10; threshold: 3/10, baseline mean pain: 6.5/10, SD: 1.6/10, and correlation: 0.44), and at its greatest, it was 0.78/10 (95% confidence interval: 0.63/10-0.94/10; threshold: 5/10, baseline mean pain: 6/10, SD: 1.8/10, and correlation: 0.19). We have shown that using pain inclusion thresholds in clinical trials drives progressively larger regression to the mean effects. We believe that a threshold of 3/10 offers the best compromise between maintaining assay sensitivity (the goal of thresholds) and the size of the regression to the mean effect.

If the doors of perception were cleansed, would chronic pain be relieved? Evaluating the benefits and risks of psychedelics

Psychedelic substances have played important roles in diverse cultures, and ingesting various plant preparations to evoke altered states of consciousness has been described throughout recorded history. Accounts of the subjective effects of psychedelics typically focus on spiritual and mystical-type experiences, including feelings of unity, sacredness, and transcendence. Over the past two decades, there has been increasing interest in psychedelics as treatments for various medical disorders, including chronic pain. Although concerns about adverse medical and psychological effects contributed to their controlled status, contemporary knowledge of psychedelics suggests that risks are relatively rare when patients are carefully screened, prepared, and supervised. Clinical trial results have provided support for the effectiveness of psychedelics in different psychiatric conditions. However, there are only a small number of generally uncontrolled studies of psychedelics in patients with chronic pain (e.g., cancer pain, phantom limb pain, migraine, and cluster headache). Challenges in evaluating psychedelics as treatments for chronic pain include identifying neurobiologic and psychosocial mechanisms of action and determining which pain conditions to investigate. Truly informative proof-of-concept and confirmatory randomized clinical trials will require careful selection of control groups, efforts to minimize bias from unblinding, and attention to the roles of patient mental set and treatment setting. Perspective: There is considerable promise for the use of psychedelic therapy for pain, but evidence-based recommendations for the design of future studies are needed to ensure that the results of this research are truly informative.

Diclofenac-hyaluronate conjugate (diclofenac etalhyaluronate) intra-articular injection for hip, ankle, shoulder, and elbow osteoarthritis: a randomized controlled trial

Background

To evaluate the efficacy and safety of intra-articular injection of diclofenac etalhyaluronate (DF-HA) in patients with osteoarthritis (OA) of the hip, ankle, shoulder, or elbow.

Methods

In this randomized, placebo-controlled, double-blind study in Japan, Japanese patients aged ≥20 years diagnosed with OA of the hip, ankle, shoulder, or elbow were randomly assigned 1:1 to DF-HA 30 mg or placebo (citric acid-sodium citrate buffered solution). Subjects received three injections of the study drug in each joint cavity every 4 weeks and were assessed for 12 weeks after the first injection. The primary endpoint was the mean change from baseline in a diary-based 11-point numerical rating scale (NRS) for pain over 12 weeks, analyzed for each joint. Treatment-emergent adverse events were recorded, and morphological changes in each joint were evaluated radiographically.

Results

The study drug (DF-HA vs placebo) was injected into 90, 60, 90, or 50 subjects with OA of the hip, ankle, shoulder, or elbow (46 vs 44, 30 vs 30, 45 vs 45, and 25 vs 25, respectively). The group differences in the mean change from baseline in the pain NRS over 12 weeks were − 0.81 (95% confidence interval: − 1.48 to − 0.13), − 0.07 (− 1.03 to 0.89), 0.15 (− 0.48 to 0.78), and 0.61 (− 0.41 to 1.62) for the hip, ankle, shoulder, and elbow joints, respectively, with statistically significant differences observed only in the hip joint. The change from baseline in the hip joint was greater with DF-HA than placebo at all time points from Weeks 1–12. No clinically significant adverse events or radiographic changes were observed.

Conclusions

Intra-articularly administered DF-HA for hip OA produced a rapid response and was safe, with analgesia maintained for 12 weeks when administered every 4 weeks.

Trial registration

JapicCTI-173,678 (First registered date: 21 August 2017).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05328-3.

On the Relationship Between Pain Variability and Relief in Randomized Clinical Trials

Previous research reports suggest greater baseline variability is associated with greater pain relief in those who receive a placebo. However, studies that evidence this association do not control for confounding effects from regression to the mean and natural history. In this report, we analyzed data from two randomized clinical trials (Placebo I and Placebo II, total N = 139) while adjusting for the effects of natural history and regression to the mean via a no treatment group. Results agree between the two placebo groups in each study: both placebo groups showed negligible semi-partial correlations between baseline variability and adjusted response [r_sp (CI_95%) = 0.22 (0.03, 0.42) and 0 (−0.07, 0.07) for Placebo I and II, respectively]. The no treatment group in Placebo I showed a negative correlation [−0.22 (−0.43, −0.02)], but the no treatment and drug groups in Placebo II's correlations were negligible [−0.02 (−0.08, 0.02) and 0.00 (−0.10, 0.12) for the no treatment and drug groups, respectively]. When modeled as a linear covariate, baseline pain variability accounted for <1% of the variance in post-intervention pain across both studies. Even after adjusting for baseline pain and natural history, the inability of baseline pain variability to account for substantial variance in pain response highlights that previous results concerning pain variability and treatment response may be inconsistent. Indeed, the relationship appears to be neither consistently specific nor sensitive to improvements in the placebo group. More work is needed to understand and establish the prognostic value of baseline pain variability—especially its placebo specificity and generalizability across patient populations.

Impact of variability in baseline pain on the placebo response in randomized, placebo-controlled, crossover trials in peripheral neuropathic pain

ABSTRACT

Large placebo responses often negatively affect randomized controlled trials within the pain area. Understanding different possible factors that influence the placebo response is therefore important. In this retrospective analysis, we hypothesized that a large variability in baseline pain score would predict a greater placebo response and analyzed the impact of the coefficient of variation, SD, and difference between the highest and lowest numeric rating scale (NRS) score at baseline on the placebo response. A total of 160 observations on placebo response from 3 controlled clinical trials with a crossover design were included in this study. In general, the placebo response was low with a mean reduction in pain intensity of 0.5 points (range -5 to 7) measured on a 0 to 10 point NRS, and only 15% were placebo responders as defined by more than 30% reduction in NRS pain score from baseline to the end of the placebo treatment period. We found no significant impact of baseline pain coefficient of variation, SD, or the difference between lowest and highest baseline pain score on the placebo response. Placebo response in one trial did not predict placebo response in another trial. A large placebo response was not associated with a large treatment response. In conclusion, in this retrospective data analysis, there was no impact of baseline pain variability on the placebo response in controlled clinical trials with a crossover design in patients with peripheral neuropathic pain.

Pragmatic trials of pain therapies: a systematic review of methods

ABSTRACT

Pragmatic randomised clinical trials aim to directly inform clinical or health policy decision making. Here, we systematically review methods and design of pragmatic trials of pain therapies to examine methods, identify common challenges, and areas for improvement. Seven databases were searched for pragmatic randomised controlled clinical trials that assessed pain treatment in a clinical population of adults reporting pain. All screening steps and data extractions were performed twice. Data were synthesised descriptively, and correlation analyses between prespecified trial features and PRECIS-2 (PRagmatic-Explanatory Continuum Indicator Summary 2) ratings and attrition were performed. Protocol registration: PROSPERO-ID CRD42020178954. Of 57 included trials, only 21% assessed pharmacological interventions, the remainder physical, surgical, psychological, or self-management pain therapies. Three-quarters of the trials were comparative effectiveness designs, often conducted in multiple centres (median: 5; Q1/3: 1, 9.25) and with a median sample size of 234 patients at randomization (Q1/3: 135.5; 363.5). Although most trials recruited patients with chronic pain, reporting of pain duration was poor and not well described. Reporting was comprehensive for most general items, while often deficient for specific pragmatic aspects. Average ratings for pragmatism were highest for treatment adherence flexibility and clinical relevance of outcome measures. They were lowest for patient recruitment methods and extent of follow-up measurements and appointments. Current practice in pragmatic trials of pain treatments can be improved in areas such as patient recruitment and reporting of methods, analysis, and interpretation of data. These improvements will facilitate translatability to other real-world settings-the purpose of pragmatic trials.

The Treatment of Painful Diabetic Neuropathy

Painful diabetic peripheral neuropathy (painful-DPN) is a highly prevalent and disabling condition, affecting up to one-third of patients with diabetes. This condition can have a profound impact resulting in a poor quality of life, disruption of employment, impaired sleep, and poor mental health with an excess of depression and anxiety. The management of painful-DPN poses a great challenge. Unfortunately, currently there are no Food and Drug Administration (USA) approved disease-modifying treatments for diabetic peripheral neuropathy (DPN) as trials of putative pathogenetic treatments have failed at phase 3 clinical trial stage. Therefore, the focus of managing painful- DPN other than improving glycaemic control and cardiovascular risk factor modification is treating symptoms. The recommended treatments based on expert international consensus for painful- DPN have remained essentially unchanged for the last decade. Both the serotonin re-uptake inhibitor (SNRI) duloxetine and α2δ ligand pregabalin have the most robust evidence for treating painful-DPN. The weak opioids (e.g. tapentadol and tramadol, both of which have an SNRI effect), tricyclic antidepressants such as amitriptyline and α2δ ligand gabapentin are also widely recommended and prescribed agents. Opioids (except tramadol and tapentadol), should be prescribed with caution in view of the lack of definitive data surrounding efficacy, concerns surrounding addiction and adverse events. Recently, emerging therapies have gained local licenses, including the α2δ ligand mirogabalin (Japan) and the high dose 8% capsaicin patch (FDA and Europe). The management of refractory painful-DPN is difficult; specialist pain services may offer off-label therapies (e.g. botulinum toxin, intravenous lidocaine and spinal cord stimulation), although there is limited clinical trial evidence supporting their use. Additionally, despite combination therapy being commonly used clinically, there is little evidence supporting this practise. There is a need for further clinical trials to assess novel therapeutic agents, optimal combination therapy and existing agents to determine which are the most effective for the treatment of painful-DPN. This article reviews the evidence for the treatment of painful-DPN, including emerging treatment strategies such as novel compounds and stratification of patients according to individual characteristics (e.g. pain phenotype, neuroimaging and genotype) to improve treatment responses.

Assessment of pain associated with chronic pancreatitis: An international consensus guideline

Pain is the most common symptom in chronic pancreatitis (CP) with a major impact on quality of life. Few validated questionnaires to assess pain in CP exist, and the lack of consensus negatively impacts clinical management, research and meta-analysis. This guideline aims to review generic pain questionnaires for their usability in CP, to outline how pain assessment can be modified by confounding factors and pain types, to assess the value of additional measures such as quality of life, mental health and quantitative sensory testing, and finally to review pain assessment questionnaires used specifically in CP. A systematic review was done to answer 27 questions that followed the PICO (Population; Intervention; Comparator; Outcome) template. Quality of evidence of the statements was judged by Grades of Recommendation, Assessment, Development and Evaluation (GRADE) criteria. The manuscript was sent for review to 36 experts from various disciplines and continents in a multi-stage Delphi process, and finally reviewed by patient representatives. Main findings were that generic pain instruments are valid in most settings, but aspects of pain are specific for CP (including in children), and instruments have to account for the wide phenotypic variability and development of sensitization of the central nervous system. Side effects to treatment and placebo effects shall also be considered. Some multidimensional questionnaires are validated for CP and are recommended together with assessment of quality of life and psychiatric co-morbidities. This guideline will result in more homogeneous and comprehensive pain assessment to potentially improve management of painful CP.

Efficacy and safety of EMA401 in peripheral neuropathic pain: results of 2 randomised, double-blind, phase 2 studies in patients with postherpetic neuralgia and painful diabetic neuropathy

ABSTRACT

The analgesic efficacy and safety of 2 phase 2b studies of EMA401 (a highly selective angiotensin II type 2 receptor antagonist) in patients with postherpetic neuralgia (EMPHENE) and painful diabetic neuropathy (EMPADINE) were reported. These were multicentre, randomised, double-blind treatment studies conducted in participants with postherpetic neuralgia or type I/II diabetes mellitus with painful distal symmetrical sensorimotor neuropathy. Participants were randomised 1:1:1 to either placebo, EMA401 25 mg, or 100 mg twice daily (b.i.d) in the EMPHENE and 1:1 to placebo or EMA401 100 mg b.i.d. in the EMPADINE. The primary outcome for both the studies was change in weekly mean of the 24-hour average pain score, using a numeric rating scale from baseline to week 12. Both the studies were prematurely terminated due to preclinical hepatotoxicity on long-term dosing, although not observed in these studies. Out of the planned participants, a total of 129/360 (EMPHENE) and 137/400 (EMPADINE) participants were enrolled. The least square mean reduction in numeric rating scale pain score was numerically in favour of EMA401 100 mg arm in both EMPHENE (treatment difference: -0.5 [95% confidence interval: -1.6 to 0.6; P value: 0.35]) and EMPADINE (treatment difference: -0.6 [95% confidence interval: -1.4 to 0.1; P value: 0.10]) at the end of week 12. However, as the studies were terminated prematurely, no firm conclusion could be drawn but the consistent clinical improvement in pain intensity reduction across these 2 studies in 2 different populations is worth noting.

Measurement properties of brief neuropathy screening items in cancer patients receiving taxanes, platinums, or proteasome inhibitors

BACKGROUND

Timely detection of chemotherapy-induced peripheral neuropathy (CIPN) is critical to effectively tailor chemotherapy dose levels and offer supportive care. The purpose of this secondary analysis was to determine the reliability and validity of the two Patient-Reported Outcomes Version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE™) numbness and tingling severity and interference items to screen for CIPN in patients receiving taxanes, platinums, or proteasome inhibitors.

METHODS

Participants (N = 142) completed the two PRO-CTCAE items, a 0-10 numerical rating scale of worst CIPN pain intensity, and the Quality of Life Questionnaire-CIPN20 (QLQ-CIPN20) prior to three clinical visits (T1, T2, T3) during neurotoxic chemotherapy. Participants completed the two PRO-CTCAE items again following the T3 clinical visit (T4). In addition, study staff administered the modified Total Neuropathy Score-Clinical Version (TNSc©) at T3. We examined floor (i.e., no CIPN severity or interference) and ceiling effects, test-retest reliability, concurrent validity, longitudinal validity, construct validity of the response categories, and sensitivity and specificity of the two PRO-CTCAE items.

RESULTS

At T3, 29% of participants had PRO-CTCAE severity scores at the floor; 60.1% of participants reported interference item scores at the floor. Agreements between scores reported at T3 and T4 for PRO-CTCAE severity (ICC = 0.79) and interference (ICC = 0.73) were moderate to strong. The PRO-CTCAE severity and interference items correlated moderately-strongly with QLQ-CIPN20 sensory (Spearman's ρ-range = 0.53-0.72) and motor (Spearman's ρ-range = 0.50-0.58) subscale scores. The Cohen's d from T1 to T3 for the PRO-CTCAE items were small (severity: d = 0.32, interference: d = 0.40) and comparable to the effect sizes for change observed with the QLQ-CIPN20. The PRO-CTCAE severity (0-3) and interference (0-2) response categories distinguished respondents with significantly different levels of QLQ-CIPN20 sensory and motor subscale scores (p < 0.001 via Jonckheere-Terpstra tests). The sensitivity and specificity of the PRO-CTCAE severity item (cutoff > 0) to detect probable sensory peripheral neuropathy were 95.83% and 65.22%, while the sensitivity and specificity of the PRO-CTCAE™ interference item (cutoff > 0) were 51.39% and 73.91%.

CONCLUSION

Preliminary evidence supports the reliability and validity of the PRO-CTCAE numbness and tingling items for CIPN screening, although there may be floor effects and limitations in the capacity of the PRO-CTCAE items to identify the full range of CIPN sensory and motor features beyond numbness and tingling. Trial Registration ClinicalTrials.Gov, NCT03514680. Registered 21 April 2018. https://clinicaltrials.gov/ct2/show/NCT03514680.

Capsaicin 179-mg cutaneous patch in the treatment of post-surgical neuropathic pain: a scoping review of current evidence and place in therapy

INTRODUCTION

The use of topical agents has been suggested for post-surgical neuropathic pain. A high-concentration capsaicin 179-mg cutaneous patch (Qutenza™) is licensed in adults for chronic neuropathic pain in the EU, and neuropathic pain with post-herpetic neuralgia and neuropathic pain with diabetic peripheral neuropathy in the USA. This article aims to describe the use of a topical capsaicin 179-mg cutaneous patch in the treatment of PSNP.

AREA COVERED

This narrative review presents the relevant clinical aspects of the use of a topical capsaicin 179-mg cutaneous patch for the treatment of post-surgical neuropathic pain (PSNP). Randomized control trials, observational studies, case series, and reports investigating the clinical use of the capsaicin patch were searched through MEDLINE, EMBASE, AMED, Cochrane Library, CINAHL, Web of Science, and ROAD databases. Trials from citation lists of reviewed articles and hand-searching were added. The search concluded in September 2020. 10/20 articles were considered.

EXPERT OPINION

Some clinical studies demonstrated the efficacy of the capsaicin 179-mg patch in PSNP as monotherapy and concomitant treatment with oral treatments. This topical treatment of PSNP is better tolerated and accepted compared with systemic treatments. To maximize the effectiveness of the treatment, correct administration recommendations should be followed.

Placebo Response Reduction and Accurate Pain Reporting Training Reduces Placebo Responses in a Clinical Trial on Chronic Low Back Pain: Results From a Comparison to the Literature

OBJECTIVE

A literature review was conducted to compare placebo responses in a recent trial-which implemented an accurate pain reporting (APR) and placebo response reduction (PRR) training program-with placebo responses in similar previous trials in chronic lower back pain (CLBP) that did not use such training.

METHODS

A literature search was performed to find parallel design, randomized, controlled trials of pharmacological treatments administered orally or through intravenous injection for CLBP. Studies were assessed for the proportion of placebo responders, defined as the proportion of patients in the placebo group with ≥30% reduction in pain intensity. A χ analysis was performed on the proportion of responders from the SPRINT trial and from other similar studies.

RESULTS

Of 844 studies identified in the initial screening process, 16 studies were included for comparison. The percentage of placebo responders was statistically significantly lower in the SPRINT study (19.1%) compared with other CLBP trials (38.0%) (P=0.003). Our results show that the placebo response was lower in the SPRINT trial than other comparable studies on CLBP.

DISCUSSION

These findings are consistent with results from other studies showing that neutralizing subject and study staff expectations of therapeutic benefit can decrease the placebo response in clinical trials. The results of this study suggest training participants and staff to improve pain reporting accuracy, neutralize expectations, and decrease external cues that may bias participants' pain ratings in clinical trials may effectively decrease the placebo response leading to increased assay sensitivity.

Combination Therapy for Neuropathic Pain: A Review of Recent Evidence

Pharmacological treatment is not very effective for neuropathic pain (NP). A progressive decrease in the estimated effect of NP drugs has been reported, giving rise to an increase in the use of the multimodal analgesic approach. We performed a new independent review to assess whether more and better-quality evidence has become available since the last systematic review. We evaluated the efficacy, tolerability, and safety of double-blinded randomized controlled trials involving only adult participants and comparing combination therapy (CT: ≥2 drugs) with a placebo and/or at least one other comparator with an NP indication. The primary outcome assessed was the proportion of participants reporting ≥50% pain reductions from baseline. The secondary outcome assessed was the proportion of drop-outs due to treatment-emergent adverse events. After removing duplicates, 2323 citations were screened, with 164 articles assessed for eligibility, from which 16 were included for qualitative analysis. From the latter, only five lasted for at least 12 weeks and only six complied with the required data for complete analysis. CT has been adopted for years without robust evidence. Efforts have been made to achieve better-quality evidence, but the quality has not improved over the years. In this regard, guidelines for NP should attempt to make recommendations about CT research, prioritizing which combinations to analyze.

Spinal Inhibitory Dysfunction in Patients With Painful or Painless Diabetic Neuropathy

OBJECTIVE

Impaired rate-dependent depression of the Hoffman reflex (HRDD) is a marker of spinal inhibitory dysfunction and has previously been associated with painful neuropathy in a proof-of-concept study in patients with type 1 diabetes. We have now undertaken an assessment of HRDD in patients with type 1 or type 2 diabetes.

RESEARCH DESIGN AND METHODS

A total of 148 participants, including 34 healthy control subjects, 42 patients with painful diabetic neuropathy, and 62 patients with diabetic neuropathy without pain, underwent an assessment of HRDD and a detailed assessment of peripheral neuropathy, including nerve conduction studies, corneal confocal microscopy, and thermal threshold testing.

RESULTS

Compared with healthy control subjects (P < 0.001) and patients without pain (P < 0.001), we found that HRDD is impaired in patients with type 1 or type 2 diabetes with neuropathic pain. These impairments are unrelated to diabetes type and the presence or severity of neuropathy. In contrast, patients without neuropathic pain (P < 0.05) exhibited enhanced HRDD compared with control subjects.

CONCLUSIONS

We suggest that loss or impairment of HRDD may help to identify a subpopulation of patients with painful diabetic neuropathy mediated by impaired spinal inhibitory systems who may respond optimally to therapies that target spinal or supraspinal mechanisms. Enhanced RDD in patients without pain may reflect engagement of spinal pain-suppressing mechanisms.

Psychophysical evaluation of somatosensory function in oro-facial pain: achievements and challenges

AIM

This critical review describes key methodological aspects for a successful oro-facial psychophysical evaluation of the somatosensory system and highlights the diagnostic value of somatosensory assessment and management perspectives based on somatosensory profiling.

METHODS

This topical review was based on a non-systematic search for studies about somatosensory evaluation in oro-facial pain in PubMed and Embase.

RESULTS

The recent progress regarding the psychophysical evaluation of somatosensory function was largely possible due to the development and application of valid, reliable and standardised psychophysical methods. Qualitative sensory testing may be useful as a screening tool to rule out relevant somatosensory abnormalities. Nevertheless, the patient should preferably be referred to a more comprehensive assessment with the quantitative sensory testing battery if confirmation of somatosensory abnormalities is necessary. Moreover, the identification of relevant somatosensory alterations in chronic pain disorders that do not fulfil the current criteria to be regarded as neuropathic has also increased the usefulness of somatosensory evaluation as a feasible method to better characterise the patients and perhaps elucidate some underpinnings of the so-called 'nociplastic' pain disorders. Finally, an additional benefit of oro-facial pain treatment based on somatosensory profiling still needs to be demonstrated and convincing evidence of somatosensory findings as predictors of treatment efficacy in chronic oro-facial pain awaits further studies.

CONCLUSION

Psychophysical evaluation of somatosensory function in oro-facial pain is still in its infancy but with a clear potential to continue to improve the assessment, diagnosis and management of oro-facial pain patients.