I. Indices of Pain Intensity Derived From Ecological Momentary Assessments: Rationale and Stakeholder Preferences

Identifying Weekly Trajectories of Pain Severity Using Daily Data From an mHealth Study: Cluster Analysis

BACKGROUND

People with chronic pain experience variability in their trajectories of pain severity. Previous studies have explored pain trajectories by clustering sparse data; however, to understand daily pain variability, there is a need to identify clusters of weekly trajectories using daily pain data. Between-week variability can be explored by quantifying the week-to-week movement between these clusters. We propose that future work can use clusters of pain severity in a forecasting model for short-term (eg, daily fluctuations) and longer-term (eg, weekly patterns) variability. Specifically, future work can use clusters of weekly trajectories to predict between-cluster movement and within-cluster variability in pain severity.

OBJECTIVE

This study aims to understand clusters of common weekly patterns as a first stage in developing a pain-forecasting model.

METHODS

Data from a population-based mobile health study were used to compile weekly pain trajectories (n=21,919) that were then clustered using a k-medoids algorithm. Sensitivity analyses tested the impact of assumptions related to the ordinal and longitudinal structure of the data. The characteristics of people within clusters were examined, and a transition analysis was conducted to understand the movement of people between consecutive weekly clusters.

RESULTS

Four clusters were identified representing trajectories of no or low pain (1714/21,919, 7.82%), mild pain (8246/21,919, 37.62%), moderate pain (8376/21,919, 38.21%), and severe pain (3583/21,919, 16.35%). Sensitivity analyses confirmed the 4-cluster solution, and the resulting clusters were similar to those in the main analysis, with at least 85% of the trajectories belonging to the same cluster as in the main analysis. Male participants spent longer (participant mean 7.9, 95% bootstrap CI 6%-9.9%) in the no or low pain cluster than female participants (participant mean 6.5, 95% bootstrap CI 5.7%-7.3%). Younger people (aged 17-24 y) spent longer (participant mean 28.3, 95% bootstrap CI 19.3%-38.5%) in the severe pain cluster than older people (aged 65-86 y; participant mean 9.8, 95% bootstrap CI 7.7%-12.3%). People with fibromyalgia (participant mean 31.5, 95% bootstrap CI 28.5%-34.4%) and neuropathic pain (participant mean 31.1, 95% bootstrap CI 27.3%-34.9%) spent longer in the severe pain cluster than those with other conditions, and people with rheumatoid arthritis spent longer (participant mean 7.8, 95% bootstrap CI 6.1%-9.6%) in the no or low pain cluster than those with other conditions. There were 12,267 pairs of consecutive weeks that contributed to the transition analysis. The empirical percentage remaining in the same cluster across consecutive weeks was 65.96% (8091/12,267). When movement between clusters occurred, the highest percentage of movement was to an adjacent cluster.

CONCLUSIONS

The clusters of pain severity identified in this study provide a parsimonious description of the weekly experiences of people with chronic pain. These clusters could be used for future study of between-cluster movement and within-cluster variability to develop accurate and stakeholder-informed pain-forecasting tools.

The Effect of Probiotics on the Management of Pain and Inflammation in Osteoarthritis: A Systematic Review and Meta-Analysis of Clinical Studies

Osteoarthritis (OA) is one of the most common musculoskeletal disorders. Recently, research has focused on the role of intestinal microbiome dysbiosis in OA. The aim of this study was to systematically review randomized intervention clinical studies investigating the effect of probiotics on the management of OA-related pain and inflammation. Pre-clinical studies and non-randomized trials were excluded. A literature search was conducted using MEDLINE, EMBASE, and Web of Science. Study quality was assessed with the Cochrane risk of bias (RoB2) tool and the Risk of Bias in N-of-1 Trials (RoBiNT) scale. RevMan was used for the meta-analysis. Outcome measures assessed self-reported pain, stiffness and impediment, and serum hs-CRP. Three studies, with 501 participants, were considered eligible for qualitative synthesis and meta-analysis. A significant reduction in symptoms across all outcomes measured, except stiffness, was evident with Lactobacillus casei Shirota. However, all other probiotics reviewed did not seem to have any effect on the measured outcomes. Pre-clinical evidence, along with the RCTs reviewed, suggests that probiotics of the Lactobacillus strains might be of use for managing pain and inflammation in OA. Considering the small number of studies included in the present review and the possible risk of bias, we conclude that further studies on the role of probiotics in humans with OA are warranted.

Momentary Emotion Regulation Strategies and Pain Experience Among Adults With Chronic Pain: An Ecological Momentary Assessment Study

OBJECTIVES

The intention of this study was to characterize the real-time momentary relationship between emotion regulation strategies and the pain experience (ie intensity, interference, and negative affect) among adults with chronic pain. Chronic pain is a significant public health concern. Psychological treatments are effective for treating chronic pain, but long-term follow-up studies are limited, and treatment effect sizes are small. Identifying modifiable treatment targets, such as emotion regulation (ER), is critical to improve interventions. ER (ie, cognitive and attentional strategies to modulate or maintain emotional experience) has been linked to psychopathology and pain experience in adults. Yet, the existing work is limited and has largely focused on the relationship between emotional experience, not ER, and pain.

MATERIALS AND METHODS

The current study utilized ecological momentary assessment 53 adults with chronic pain. Participants completed ecological momentary assessments of pain experience and ER strategies 5 times a day for 7 days. Associations by specific strategy type were also examined, highlighting the importance of worry, experiential avoidance, rumination, and expressive suppression in pain experience.

RESULTS

Results of the current study provide evidence for the association between within-person maladaptive ER strategies and pain intensity ( b = 2.11, SE = 0.37, P < 0.001), pain interference ( b = 1.25, SE = 0.40, P = 0.002), and pain-related negative affect ( b = 2.20, SE = 0.41, P < 0.001). (77.4% females; M age = 27.10 y, SD = 5.16 y).

DISCUSSION

Given that ER is readily targeted in psychological treatments for chronic pain, the results from the current study provide initial evidence to target these ER strategies in treatment.

Ecological momentary assessment of pelvic pain and urinary urgency variability in urologic chronic pelvic pain syndrome and their association with illness impact and quality of life: Findings from the multidisciplinary approach to the study of chronic pelvic pain symptom patterns study

PURPOSE

This study tested the hypothesis that ecological momentary assessment (EMA) of pelvic pain (PP) and urinary urgency (UU) would reveal unique Urologic Chronic Pelvic Pain Syndrome (UCPPS) phenotypes that would be associated with disease specific quality of life (QOL) and illness impact metrics (IIM).

MATERIALS AND METHODS

A previously validated smart phone app (M-app) was provided to willing Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) participants. M-app notifications were sent 4-times daily for 14 days inquiring about PP and UU severity. A clustering algorithm that accounted for variance placed participants into PP and UU variability? clusters. Associations between clusters and QOL and IIM were then determined.

RESULTS

A total of 204 participants enrolled in the M-app study (64% female). M-app compliance was high (median 63% of surveys). Cluster analysis revealed k = 3 (high, low, none) PP clusters and k = 2 (high, low) UU clusters. When adjusting for baseline pain severity, high PP variability, but not UU variability, was strongly associated with QOL and IIM; specifically worse mood, worse sleep and higher anxiety. UU and PP clusters were associated with each other (p < 0.0001), but a large percentage (33%) of patients with high PP variability had low UU variability.

CONCLUSIONS

PP variability is an independent predictor of worse QOL and more severe IIM in UCPPS participants after controlling for baseline pain severity and UU. These findings suggest alternative pain indices, such as pain variability and unpredictability, may be useful adjuncts to traditional measures of worst and average pain when assessing UCPPS treatment responses.

Cognitive flexibility training for chronic pain: a randomized clinical study

Introduction

Previous studies suggest an association between cognitive flexibility and development of chronic pain after surgery. It is not known whether cognitive flexibility can be improved in patients with chronic pain.

Objectives

This study tested whether a neurocognitive training program results in improved cognitive flexibility and pain in patients with chronic pain.

Methods

We conducted a single-center, prospective, randomized study investigating 5-week daily neurocognitive training in patients with chronic pain. Participants (n = 145) were randomized into neurocognitive training or care as usual, and they completed assessments at baseline, posttreatment, and 3 months. The treatment group was asked to spend 35 minutes daily completing a program with tasks on cognitive flexibility, memory, attention, and speed. The primary outcome was performance on the neurocognitive performance test (NCPT). Secondary outcomes included levels of pain interference and severity.

Results

At 5 weeks, the treatment group showed greater improvements on NCPT compared with the control group (d = 0.37); effect size was smaller at 3 months (d = 0.18). The treatment group reported lower pain severity at 5 weeks (d = 0.16) and 3 months (d = 0.39) than the control group, but pain interference was only lower at 3 months (d = 0.20).

Conclusions

Outcomes suggest that using neurocognitive training to modify cognitive flexibility in patients with chronic pain may improve pain severity. This study provided effect size estimates to inform sample size calculations for randomized controlled trials to test the effectiveness of neurocognitive interventions for the prevention and treatment of chronic pain.

The level of agreement between the numerical rating scale and visual analogue scale for assessing pain intensity in adults with chronic pain

The numerical rating scale and visual analogue scale are used to quantify pain intensity. However, it has not yet been explored whether these scores are interchangeable in adults with chronic pain. Data from the prospective multicentre cross-sectional INTERVAL study were used to evaluate the one-dimensionality and agreement between numerical rating scale scores and visual analogue scale scores in adults with chronic pain. Pain intensity scores using the numerical rating scale and visual analogue scale were provided by 366 patients with chronic pain for current, average, minimal and maximal pain. To evaluate whether pain intensity scales are completed in accordance with each other, the proportion of patients who satisfied the following condition was calculated: minimal pain intensity ≤ maximal pain intensity. A factor analysis confirmed the one-dimensionality of the pain measures. A significant difference was found between numerical rating scale and visual analogue scale scores for average, current, minimum and maximum pain. Intra-class correlation coefficient estimates ranged from 0.739 to 0.858 and all measures failed to show sufficient and acceptable agreement at the 95% level. The strength of agreement between pain severity categories was classified as 'moderate' for average and minimal pain and 'substantial' for current and maximal pain. The proportion of patients who scored minimal pain ≤ maximal pain was 97.5% for the numerical rating scale and 89.5% for the visual analogue scale. This study failed to show an acceptable agreement between the numerical rating scale and visual analogue scale when pain intensity was rated by adults with chronic pain, despite showing both scales measure the same information.

Daily Pain Experiences in Chronic Pancreatitis: Identifying Pain Phenotypes

OBJECTIVES

Pain, the hallmark symptom of chronic pancreatitis (CP), remains difficult to assess. To capture the variability of pain that patients can experience day to day, this study used pain diaries to describe daily pain experiences and identify pain phenotypes.

METHODS

This study is a secondary data analysis from a pilot trial examining cognitive behavioral therapy for pain treatment in CP. Before treatment, patients completed an online daily pain diary using the Brief Pain Inventory for 7 days. Using indicators of pain magnitude, pain variability, pain synchrony along with least, worst, and average pain intensity levels, we identified pain patterns using K-means clustering.

RESULTS

Of 30 patients in the pilot trial, a total of 27 patients (mean age of 49.8 years, 80% women) had complete data to include in this report. Four clusters were identified: cluster 1, lowest pain magnitude (n = 3); cluster 2, moderate pain magnitude and high pain variability (n = 4); cluster 3, moderate pain magnitude and low pain variability (n = 9); and cluster 4, highest pain magnitude and lowest pain variability (n = 11).

CONCLUSIONS

Daily pain diaries offer a novel way of evaluating the dynamic pain experiences in CP. Although 4 distinct pain patterns were identified, further studies are needed to validate these findings.

Presence and grade of undertreatment of pain in children with cerebral palsy

OBJECTIVES

To investigate if chronic pain in children with cerebral palsy is undertreated with the current pharmacological/non-pharmacological interventions using a pain management index.

METHODS

Parents of 120 children with cerebral palsy between the ages of 2-19 years from our region in Denmark answered a questionnaire about whether their child had everyday pain. When answering in pain, we inquired about pain status and pharmacological/non-pharmacological pain coping interventions. Everyday pain was viewed as chronic pain with acute exacerbations. Pain experienced was divided into worst pain (highest moments of pain intensity) and least pain (lowest moments of pain intensity). To describe and evaluate the effectiveness of pain interventions used, a pain management index was utilized. Everyday pain was assessed using a logistical regression by adjusting for age, sex, and gross motor function classification system level.

RESULTS

59/115 (0.51) of parents answering the questionnaire reported everyday pain. Of those, the median age was 10 years. For pain alleviation, massage was reported by parents as being used by 29/59 (0.49) children and paracetamol by 21/59 (0.36). Pain affected daily life in 44/59 (0.75). By our evaluation 44/59 (0.75) were inadequately treated for their pain. Our evaluation also revealed that 19/59 (0.32) of children in pain had inadequately treated pain combined with an undesirable intensity of least pain.

CONCLUSIONS

Half of the children with cerebral palsy experienced chronic pain according to our pain questionnaire answered by parents. Among these children three-quarters were insufficiently treated for their pain. In the same group, one-third were impacted by pain felt at both its highest and lowest moments of intensity. Massage therapy and paracetamol were the most frequently utilized pain-alleviating interventions. In our cohort, pain was undertreated and likely underdiagnose (Protocol number H-17008823).

Feasibility and Acceptability of a Preoperative Multimodal Mobile Health Assessment in Spine Surgery Candidates

BACKGROUND

Rapid growth in smartphone use has expanded opportunities to use mobile health (mHealth) technology to collect real-time patient-reported and objective biometric data. These data may have important implication for personalized treatments of degenerative spine disease. However, no large-scale study has examined the feasibility and acceptability of these methods in spine surgery patients.

OBJECTIVE

To evaluate the feasibility and acceptability of a multimodal preoperative mHealth assessment in patients with degenerative spine disease.

METHODS

Adults undergoing elective spine surgery were provided with Fitbit trackers and sent preoperative ecological momentary assessments (EMAs) assessing pain, disability, mood, and catastrophizing 5 times daily for 3 weeks. Objective adherence rates and a subjective acceptability survey were used to evaluate feasibility of these methods.

RESULTS

The 77 included participants completed an average of 82 EMAs each, with an average completion rate of 86%. Younger age and chronic pulmonary disease were significantly associated with lower EMA adherence. Seventy-two (93%) participants completed Fitbit monitoring and wore the Fitbits for an average of 247 hours each. On average, participants wore the Fitbits for at least 12 hours per day for 15 days. Only worse mood scores were independently associated with lower Fitbit adherence. Most participants endorsed positive experiences with the study protocol, including 91% who said they would be willing to complete EMAs to improve their preoperative surgical guidance.

CONCLUSION

Spine fusion candidates successfully completed a preoperative multimodal mHealth assessment with high acceptability. The intensive longitudinal data collected may provide new insights that improve patient selection and treatment guidance.

Rethinking the definition of chronic postsurgical pain: composites of patient-reported pain-related outcomes vs pain intensities alone

ABSTRACT

Chronic postsurgical pain (CPSP) is defined by pain intensity and pain-related functional interference. This study included measures of function in a composite score of patient-reported outcomes (PROs) to investigate the incidence of CPSP. Registry data were analyzed for PROs 1 day and 12 months postoperatively. Based on pain intensity and pain-related interference with function, patients were allocated to the groups " CPSPF " (at least moderate pain with interference), " mixed " (milder symptoms), and " no CPSPF ". The incidence of CPSPF was compared with CPSP rates referring to published data. Variables associated with the PRO-12 score (composite PROs at 12 months; numeric rating scale 0-10) were analyzed by linear regression analysis. Of 2319 patients, 8.6%, 32.5%, and 58.9% were allocated to the groups CPSPF , mixed , and no CPSPF , respectively. Exclusion of patients whose pain scores did not increase compared with the preoperative status, resulted in a 3.3% incidence. Of the patients without pre-existing pain, 4.1% had CPSPF. Previously published pain cutoffs of numeric rating scale >0, ≥3, or ≥4, used to define CPSP, produced rates of 37.5%, 9.7%, and 5.7%. Pre-existing chronic pain, preoperative opioid medication, and type of surgery were associated with the PRO-12 score (all P < 0.05). Opioid doses and PROs 24 hours postoperatively improved the fit of the regression model. A more comprehensive assessment of pain and interference resulted in lower CPSP rates than previously reported. Although inclusion of CPSP in the ICD-11 is a welcome step, evaluation of pain characteristics would be helpful in differentiation between CPSPF and continuation of pre-existing chronic pain.

Data visualization as an intervention for pediatric chronic pain: a pilot feasibility study protocol for a randomized controlled crossover trial

Background

Chronic pain is a common and costly condition in youth, associated with negative implications that reach far beyond the pain experience itself (e.g., interference with recreational, social, and academic activities, mental health sequelae). As a self-appraised condition, pain experience is influenced by patient’s biases and meaning-making in relation to their symptoms and triggers. We propose that interacting with self-reported data will impact the experience of pain by altering understanding and expectations of symptom experience and how pain interacts with other factors (e.g., sleep, emotions, social interactions). In this study, we aim to establish the feasibility and acceptability of using a data visualization platform to track and monitor symptoms and their relationship with other factors, versus simply daily reporting of symptoms using a smartphone-based Ecological Momentary Assessment (EMA).

Methods

This protocol is for a randomized, single-center, open-label crossover trial. We aim to recruit 50 typically developing youth aged 12–18 years with chronic pain to take part in two phases of data collection. The trial will utilize an A-B counterbalanced design in which participants will be randomly assigned to receive either Part A (EMA alone for 7 days) or Part B (EMA plus visualization platform for 7 days) first and then receive the opposite phase after a 7-day break (washout period). Key outcomes will be participant reports of acceptability and feasibility, EMA completion rates, barriers, and perceptions of the benefits or risks of participation. Secondary exploratory analyses will examine the relationship between EMA-reported symptoms over time and in relation to baseline measures, as well as pilot data on any improvements in symptoms related to engaging with the data visualization platform.

Discussion

This protocol describes the feasibility and pilot testing of a novel approach to promoting self-management and facilitating symptom appraisal using visualized data. We aim to determine whether there is a sufficient rationale, both from the perspective of feasibility and patient satisfaction/acceptability, to conduct a larger randomized controlled trial of this intervention. This intervention has the potential to support clinical care for youth with chronic pain and other conditions where self-appraisal and understanding of symptom patterns are a critical component of functional recovery.

Trial registration

Open Science Framework doi: 10.17605/OSF.IO/HQX7C. Registered on October 25, 2021, osf.io/hqx7c

Supplementary Information

The online version contains supplementary material available at 10.1186/s40814-022-01170-5.

An Ecological Momentary Assessment Study of Pain Intensity Variability: Ascertaining Extent, Predictors, and Associations With Quality of Life, Interference and Health Care Utilization Among Individuals Living With Chronic Low Back Pain

This ecological momentary assessment (EMA) study examined the extent of pain intensity variability among 140 individuals with chronic low back pain and explored predictors of such variability and psychosocial and health care utilization outcomes. Individuals completed momentary pain intensity reports (0-10 numeric rating scale) several times daily for two periods of seven consecutive days, one month apart. Participants also completed online questionnaires at baseline which tapped into pain characteristics, pain-related catastrophization, kinesiophobia, activity patterns, and depression and anxiety symptoms. Questionnaires assessing quality of life and health care utilization were administered online one month after completion of the last EMA report. Data were analyzed using linear hierarchical location-scale models. Results showed that pain intensity fluctuated over the course of a week as shown by an average standard deviation of 1.2. The extent of variability in pain intensity scores was heterogeneous across participants but stable over assessment periods. Patients' baseline characteristics along with psychosocial and health care utilization outcomes were not significantly associated with pain intensity variability. We conclude that pain intensity variability differs across patients yet correlates remain elusive. There is an important gap in our knowledge of what affects this variability. Future EMA studies should replicate and extend current findings. PERSPECTIVE: This study provides evidence indicating that there is substantial variability in momentary reports of pain intensity among individuals living with chronic low back pain. However, risk and protective factors for greater lability of pain are elusive as is evidence that greater pain intensity variability results in differential health care utilization.

Reduction in migraine pain intensity in patients treated with erenumab: A post hoc analysis of two pivotal randomized studies

BACKGROUND

Erenumab (erenumab-aooe in the US) effectively reduces monthly migraine days in episodic and chronic migraine. This traditional outcome does not capture the intensity of headache pain on days with migraine.

METHODS

This post hoc analysis of two pivotal randomized, placebo-controlled studies in patients with episodic migraine and chronic migraine examined the effect of erenumab 70 and 140 mg on migraine pain. Cumulative monthly migraine pain intensity is the sum of the peak pain intensity scores (0 = no migraine to 3 = migraine day with severe pain) on migraine days. Change from baseline in cumulative monthly migraine pain and average monthly pain intensity was assessed over months 4 to 6 for episodic migraine and month 3 for chronic migraine; change in average monthly pain intensity was assessed among monthly migraine days responders/non-responders.

RESULTS

Efficacy analysis included 946 patients for the episodic migraine study and 656 patients for the chronic migraine study. Cumulative monthly migraine pain decreased significantly with erenumab versus placebo (p < 0.001, for episodic migraine and chronic migraine). In addition, monthly average migraine pain intensity decreased significantly with erenumab versus placebo for episodic migraine (p < 0.01); decreases were non-significant for chronic migraine. In comparison with placebo-treated patients, a greater proportion of erenumab-treated patients were pain intensity responders regardless of threshold used. Episodic migraine and chronic migraine patients with a ≥50% reduction in monthly migraine days (responders) had a greater reduction in monthly average pain intensity than non-responders.

CONCLUSIONS

Erenumab reduced cumulative monthly migraine pain in episodic migraine and chronic migraine patients and significantly reduced monthly average migraine pain in episodic migraine, demonstrating treatment benefit beyond reduction in migraine frequency.Clinical Trial Registration: ClinicalTrials.gov, NCT02456740; ClinicalTrials.gov, NCT02066415.

Beyond Average: Providers' Assessments of Indices for Measuring Pain Intensity in Patients With Chronic Pain

Introduction: Effective clinical care for chronic pain requires accurate, comprehensive, meaningful pain assessment. This study investigated healthcare providers' perspectives on seven pain measurement indices for capturing pain intensity.

Methods: Semi-structured telephone interviews were conducted with a purposeful sample from four US regions of 20 healthcare providers who treat patients with chronic pain. The qualitative interview guide included open-ended questions to address perspectives on pain measurement, and included quantitative ratings of the importance of seven indices [average pain, worst pain, least pain, time in no/low pain, time in high pain, fluctuating pain, unpredictable pain]. Qualitative interview data were read, coded and analyzed for themes and final interpretation. Standard quantitative methods were used to analyze index importance ratings.

Results: Despite concerns regarding 10-point visual analog and numeric rating scales, almost all providers used them. Providers most commonly asked about average pain, although they expressed misgivings about patient reporting and the index's informational value. Some supplemented average with worst and least pain, and most believed pain intensity is best understood within the context of patient functioning. Worst pain received the highest mean importance rating (7.60), average pain the second lowest rating (5.65), and unpredictable pain the lowest rating (5.20).

Discussion: Assessing average pain intensity obviates obtaining clinical insight into daily contextual factors relating to pain and functioning. Pain index use, together with timing, functionality and disability, may be most effective for understanding the meaning to patients of high pain, how pain affects their life, how life affects their pain, and how pain changes and responds to treatment.

II. Indices of Pain Intensity Derived From Ecological Momentary Assessments and Their Relationships With Patient Functioning: An Individual Patient Data Meta-analysis

Pain intensity is a complex and dynamic experience. A focus on assessing patients' average pain levels may miss important aspects of pain that impact functioning in daily life. In this second of 3 articles investigating alternative indices of pain intensity derived from Ecological Momentary Assessments (EMA), we examine the indices' associations with physical and psychosocial functioning. EMA data from 10 studies (2,660 patients) were reanalyzed to construct indices of Average Pain, Maximum Pain, Minimum Pain, Pain Variability, Time in High Pain, Time in Low Pain, Pain after Wake-up. Three sets of individual patient data meta-analyses examined 1) the test-retest reliability of the pain indices, 2) their convergent validity in relation to physical functioning, fatigue, depression, mental health, and social functioning, and 3) the incremental validity of alternative indices above Average Pain. Reliabilities approaching or exceeding a level of .7 were observed for all indices, and most correlated significantly with all functioning domains, with small to medium effect sizes. Controlling for Average Pain, Maximum Pain and Pain Variability uniquely predicted all functioning measures, and Time in High Pain predicted physical and social functioning. We suggest that alternative pain indices can provide new perspectives for understanding functioning in chronic pain. PERSPECTIVE: Alternative summary measures of pain intensity derived from EMA have the potential to help better understand patients' pain experience. Utilizing EMA for the assessment of Maximum Pain, Pain Variability, and Time in High Pain may provide an enhanced window into the relationships between pain and patients' physical and psychosocial functioning.

III. Detecting Treatment Effects in Clinical Trials With Different Indices of Pain Intensity Derived From Ecological Momentary Assessment

Pain intensity represents the primary outcome in most pain clinical trials. Identifying methods to measure aspects of pain that are most sensitive to treatment may facilitate discovery of effective interventions. In this third of 3 articles examining alternative indices of pain intensity derived from ecological momentary assessments (EMA), we compare treatment effects based on Average Pain, Maximum Pain, Minimum Pain, Pain Variability, Time in High Pain, Time in Low Pain, and Pain After Wake-Up. We also examine which indices contribute to Patient Global Impressions of Change (PGIC). Data came from 2 randomized, double-blind, placebo-controlled trials examining the efficacy of milnacipran for fibromyalgia treatment; 2,084 patients provided >1 million EMA pain intensity ratings over 24 (Study 1) or 26 (Study 2) treatment weeks. Pain Variability and Time in High Pain produced significantly smaller treatment effects than Average Pain; other pain indices showed effects that were numerically smaller, but not significantly different from Average Pain. Changes in all pain indices were significantly associated with PGIC, with improvements in Maximum Pain and in Pain Variability offering small incremental contributions to understanding PGIC over Average Pain. Results suggest that different pain indices could be used to detect treatment effects in pain clinical trials. PERSPECTIVE: Alternative summary measures of pain intensity derived from EMA may broaden the scope of outcomes useful in pain clinical trials. In this analysis of a pharmacological treatment for fibromyalgia, most pain summary measures indicated similar effects; improvements in Maximum Pain and Pain Variability contributed to understanding PGIC over Average Pain.