Pain tolerance as a predictor of outcome following multidisciplinary treatment for chronic pain: differential effects as a function of sex

Pressure algometry in the general adult population: Age and sex differences

Experimental pain studies have revealed inter-individual variations in pain perception that are influenced by age, sex, and country of origin. This study aimed to explore the age and sex differences in pressure pain thresholds within the Iranian general population. To assess the pressure pain thresholds, a handheld pressure algometer was applied bilaterally to the middle fingers of both hands. The participants also completed the short form of the McGill Pain Questionnaire to provide a clinical pain rating. This cross-sectional study included 1610 adult subjects (54.96% female, mean age 40.13 ± 10.18 years). The findings indicated that females generally exhibited lower pain thresholds than males when assessing pain detection and tolerance parameters (P < .001). Females also demonstrated a significant lower pressure thresholds and clinical pain ratings compared with men (P < .001). Additionally, significant differences were observed between age groups in terms of pain detection and tolerance thresholds (P = .02 and P = .03, respectively). However, the interaction between sex and age was not significant. No significant differences in pain detection thresholds were observed between the right and left hand (P = .11). This study underscores the potential utility of algometry as a valuable tool for objectifying pain in the Iranian population.

The Association of Preoperative Hip Pain Duration With Delayed Achievement of Clinically Significant Outcomes After Hip Arthroscopic Surgery for Femoroacetabular Impingement Syndrome

BACKGROUND

Patients with hip pain ≥2 years before hip arthroscopic surgery for femoroacetabular impingement syndrome (FAIS) have been shown to achieve inferior short-term and midterm outcomes compared with patients with a shorter pain duration, although there is limited literature that has evaluated the time to achieve clinically significant outcomes (CSOs) in this population.

PURPOSE

To compare the time to achieve CSOs after hip arthroscopic surgery for FAIS in patients with and without prolonged hip pain and to identify independent predictors of the delayed achievement of CSOs.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients who underwent primary hip arthroscopic surgery for FAIS between January 2012 and July 2019 with 6-month, 1-year, and 2-year Hip Outcome Score-Activities of Daily Living (HOS-ADL) and Hip Outcome Score-Sports Subscale (HOS-SS) scores were identified. Patients with prolonged hip pain (preoperative duration ≥2 years) were propensity score matched to a control group (preoperative duration <2 years), controlling for age, sex, and body mass index (BMI). The times to achieve the minimal clinically important difference and Patient Acceptable Symptom State were compared between groups using Kaplan-Meier survival analysis. Multivariate Cox regression considering age, sex, BMI, pain duration, activity level, and chondral status was used to identify independent predictors of the delayed achievement of CSOs.

RESULTS

A total of 179 patients with prolonged hip pain were matched to 179 control patients (mean pain duration, 60.5 ± 51.2 vs 9.7 ± 5.1 months, respectively; P < .001) of a similar age, sex, and BMI (P≥ .488) with similar baseline HOS-ADL and HOS-SS scores (P≥ .971). The prolonged hip pain group showed delayed achievement of the minimal clinically important difference and Patient Acceptable Symptom State for both the HOS-ADL and HOS-SS on Kaplan-Meier analysis (P≤ .020). On multivariate Cox regression, hip pain duration ≥2 years was shown to be an independent predictor of the delayed achievement of CSOs, with hazard ratios ranging from 1.32 to 1.65 (P≤ .029). Additional independent predictors of the delayed achievement of CSOs included increasing age, increasing BMI, female sex, self-endorsed weekly participation in physical activity, and high-grade chondral defects (hazard ratio range, 1.01-4.89; P≤ .045).

CONCLUSION

Findings from this study demonstrate that preoperative hip pain duration ≥2 years was an independent predictor of the delayed achievement of CSOs after primary hip arthroscopic surgery for FAIS.

Sex-dependent effect of inflammatory pain on negative affective states is prevented by kappa opioid receptors blockade in the nucleus accumbens shell

Pain comorbidities include several psychological disorders, such as anxiety and anhedonia. However, the way pain affects male and female individuals and by which mechanism is not well understood. Previous research shows that pain induces alterations in the dynorphinergic pathway within the mesocorticolimbic system (MCLS), together with a relationship between corticotropin-releasing system and dynorphin release in the MCLS. Here, we analyse the sex and time course-dependent effects of pain on negative affect. Additionally, we study the implication of dynorphinergic and corticotropin releasing factor in these pain related behaviours. We used behavioural pharmacology and biochemical tools to characterise negative affective states induced by inflammatory pain in male and female rats, and the alterations in the dynorphinergic and the corticotropin systems within the MCLS. Female rats showed persistent anxiety-like and reversible anhedonia-like behaviours derived from inflammatory pain. Additionally, we found alterations in dynorphin and corticotropin releasing factor in NAc and amygdala, which suggests sex-dependent dynamic adaptations. Finally blockade on the kappa opioid receptor in the NAc confirmed its role in pain-induced anxiety-like behaviour in female rats. Our results show sex and time-dependent anxiety- and anhedonia-like behaviours induced by the presence of pain in female rats. Furthermore, we replicated previous data, pointing to the KOR/DYN recruitment in the NAc as a key neurological substrate mediating pain-induced behavioural alterations. This research studies the mechanisms underlying these behaviours, to better understand the emotional dimension of pain.

Genome-wide association study on pharmacological outcomes of musculoskeletal pain in UK Biobank

The pharmacological management of musculoskeletal pain starts with NSAIDs, followed by weak or strong opioids until the pain is under control. However, the treatment outcome is usually unsatisfying due to inter-individual differences. To investigate the genetic component of treatment outcome differences, we performed a genome-wide association study (GWAS) in ~23,000 participants with musculoskeletal pain from the UK Biobank. NSAID vs. opioid users were compared as a reflection of the treatment outcome of NSAIDs. We identified one genome-wide significant hit in chromosome 4 (rs549224715, P = 3.88 × 10-8). Suggestive significant (P < 1 × 10-6) loci were functionally annotated to 18 target genes, including four genes linked to neuropathic pain processes or musculoskeletal development. Pathway and network analyses identified immunity-related processes and a (putative) central role of EGFR. However, this study should be viewed as a first step to elucidate the genetic background of musculoskeletal pain treatment.

A systematic review of genome-wide association studies for pain, nociception, neuropathy, and pain treatment responses

ABSTRACT

Pain is the leading cause of disability worldwide, imposing an enormous burden on personal health and society. Pain is a multifactorial and multidimensional problem. Currently, there is (some) evidence that genetic factors could partially explain individual susceptibility to pain and interpersonal differences in pain treatment response. To better understand the underlying genetic mechanisms of pain, we systematically reviewed and summarized genome-wide association studies (GWASes) investigating the associations between genetic variants and pain/pain-related phenotypes in humans. We reviewed 57 full-text articles and identified 30 loci reported in more than 1 study. To check whether genes described in this review are associated with (other) pain phenotypes, we searched 2 pain genetic databases, Human Pain Genetics Database and Mouse Pain Genetics Database. Six GWAS-identified genes/loci were also reported in those databases, mainly involved in neurological functions and inflammation. These findings demonstrate an important contribution of genetic factors to the risk of pain and pain-related phenotypes. However, replication studies with consistent phenotype definitions and sufficient statistical power are required to validate these pain-associated genes further. Our review also highlights the need for bioinformatic tools to elucidate the function of identified genes/loci. We believe that a better understanding of the genetic background of pain will shed light on the underlying biological mechanisms of pain and benefit patients by improving the clinical management of pain.

Pain sensitivity after Roux-en-Y gastric bypass - associations with chronic abdominal pain and psychosocial aspects

OBJECTIVES

The aims of this study were to investigate modifications in pain sensitivity after RYGB and to explore associations between pain sensitivity and weight loss, chronic abdominal pain, total body pain, anxiety, depression, and pain catastrophizing.

METHODS

In total, 163 patients with obesity were examined with a cold pressor test for pain sensitivity before and two years after RYGB. Two aspects of pain sensitivity were registered: Pain intensity (numeric rating scale, range 0-10) and pain tolerance (seconds). Associations between pain sensitivity and the explanatory variables were assessed with linear regression.

RESULTS

Two years after RYGB the pain intensity increased (mean ± SD 0.64 ± 1.9 score units, p<0.001). Pain tolerance decreased (7.2 ± 32.4 s, p=0.005). A larger reduction in body mass index was associated with increased pain intensity, β=-0.090 (95 % CI -0.15 to -0.031, p=0.003), and decreased pain tolerance β=1.1 (95 % CI 0.95 to 2.2, p=0.03). Before surgery, participants with chronic abdominal pain reported 1.2 ± 0.5 higher pain intensity (p=0.02) and had 19.2 ± 9.3 s lower pain tolerance (p=0.04) than those without abdominal pain. No differences in pain sensitivity were observed between participants who did or did not develop chronic abdominal pain after RYGB. Pain sensitivity was associated with symptoms of anxiety but not with pain catastrophizing, depression or bodily pain.

CONCLUSIONS

The pain sensitivity increased after RYGB and was associated with larger weight loss and anxiety symptoms. Changes in pain sensitivity were not associated with development of chronic abdominal pain after RYGB in our study.

Intraindividual change in pain tolerance and negative affect over 20 years: findings from the MIDUS study

Pain tolerance, defined as the ability to withstand physical pain states, is a clinically important psychobiological process associated with several deleterious outcomes, including increased pain experience, mental health problems, physical health problems, and substance use. A significant body of experimental work indicates that negative affect is associated with pain tolerance, such that increased negative affect is associated with decreased pain tolerance. Although research has documented the associations between pain tolerance and negative affect, little work has examined these associations over time, and how change in pain tolerance is related to changes in negative affect. Therefore, the current study examined the relationship between intraindividual change in self-reported pain tolerance and intraindividual change in negative affect over 20 years in a large, longitudinal, observation-based national sample of adults (n = 4,665, Mage = 46.78, SD =12.50, 53.8% female). Results from parallel process latent growth curve models indicated that slope of pain tolerance and negative affect were associated with each other over time (r = .272, 95% CI [.08, .46] p = .006). Cohen's d effect size estimates provide initial, correlational evidence that changes in pain tolerance may precede changes in negative affect. Given the relevance of pain tolerance to deleterious health outcomes, better understanding how individual difference factors, including negative affect, influence pain tolerance over time, are clinically important to reduce disease-related burden.

Mirror Therapy in Patients with Somatoform Pain Disorders-A Pilot Study

Patients with chronic pain report reduced quality of life and high symptom burden while often responding insufficiently to treatment options. Mirror therapy has been proven to be effective in treating phantom limb pain and other conditions such as CRPS. This study was designed to investigate the efficacy of mirror therapy in patients with somatoform pain disorders on symptom severity and associated physiological parameters. Fifteen patients with persistent somatoform pain disorder (F45.40) or chronic pain disorder with somatic and psychological factors (F45.41) participated and received four weeks of tablet-based mirror therapy. Symptom severity was measured with established questionnaires, and their thermal detection, pain thresholds, and heart rate variability (HRV) were also assessed. After mirror therapy, pain intensity was reduced (z = -2.878, p = 0.004), and pain thresholds for cold stimuli were also diminished, i.e., the subjects became more sensitive to cold stimuli (z = -2.040, p = 0.041). In addition, a reduction of absolute power in the low-frequency band of HRV (t(13) = 2.536, p = 0.025) was detected. These findings indicate that this intervention may reduce pain intensity and modulate associated physiological parameters. As these results are limited by several factors, e.g., a small sample size and no control group, they should be validated in further studies investigating this novel intervention in these patients.

Sex differences in interdisciplinary pain rehabilitation outcomes: a systematic review

OBJECTIVES

Interdisciplinary pain rehabilitation programs (IPRPs) are evidence-based treatments for chronic pain. Previous research has demonstrated that initial presentations of adult men and women admitted to IPRPs differ, but less is known about sex differences in IPRP treatment outcomes. To summarize and synthesize the current literature base on this topic, a systematic literature review was conducted that asked: are sex differences present in participant outcomes upon completion of interdisciplinary pain rehabilitation programs for cisgender patients? Four core domains of outcome measures were assessed: depression, pain catastrophizing, pain interference, and pain intensity/severity.

METHODS

Relevant studies meeting inclusion criteria were identified using a computer-aided search of the following electronic bibliographic databases: PubMed (MEDLINE), EMBASE, PsycINFO, CENTRAL (via Wiley Online Library), and CINAHL (via EBSCOhost). The reference list of relevant studies identified in the electronic searches was also screened to identify further studies.

RESULTS

This review concluded that most studies did not find any differences related to sex using the four outcome measures included in this review. This implies that specific considerations based on sex may not be needed when providing interdisciplinary pain rehabilitation.

CONCLUSIONS

Future research directions include comparison of additional outcome measures and exploring sex and gender issues in IPRP treatment in other formats than as a simple dichotomous variable.

Validation and Cross-Cultural Adaptation of the Spanish Version of the Pain Sensitivity Questionnaire (PSQ-S)

Experimental pain testing requires specific equipment and may be uncomfortable for patients. The Pain Sensitivity Questionnaire (PSQ) was developed to assess pain sensitivity, based on the pain intensity ratings (range: 0–10) of painful situations that occur in daily life. The main objective of this study was to carry out a cross-cultural adaptation and validation of the Spanish version of the PSQ (PSQ-S). A total of 354 subjects (296 healthy and 58 chronic pain patients) filled in the PSQ-S. A subgroup of 116 subjects performed experimental pain testing, including two modalities (cold and pressure), with different measures: pain intensity rating, pressure pain threshold, and tolerance. The validation results showed two factors: PSQ-S-moderate and PSQ-S-minor and, for the total scale and the two factors, an excellent internal consistency (Cronbach’s alpha coefficient > 0.9) and a substantial reliability (Intraclass Correlation Coefficient > 0.8). We obtained strong correlations with all the experimental pain rating parameters, catastrophizing, and depression variables, as well as moderate correlations with anxiety, central sensibilization, and impact on the quality of life. Chronic pain patients received elevated PSQ-S scores compared to healthy controls, and three cut-off values (PSQ-S-total = 7.00, PSQ-S-moderate = 7.57, and PSQ-S-minor = 6.29) based on ROC curve analyses were shown to be able to discriminate between healthy adults and adults with chronic pain. Therefore, PSQ-S may be a simple alternative to experimental pain procedures for clinical and experimental pain research.

Validation of the Turkish version of the Pain Sensitivity Questionnaire in patients with chronic pain

Objective

The Pain Sensitivity Questionnaire (PSQ) is a clinically beneficial instrument that has been proven to be correlated with various experimental pain sensitivity assessments in healthy people and in patients with chronic pain. In this study, we aimed to translate the PSQ into Turkish (PSQ-T) and validate it for the measurement of pain sensitivity among Turkish people.

Methods

Seventy-three patients with chronic back pain who were planning to undergo an interventional procedure completed the Brief Pain Inventory-Short Form (BPI-SF), Beck Depression Inventory (BDI), Beck Anxiety Inventory, Pain Catastrophizing Scale, and PSQ prior to their procedure. Subcutaneous infiltration of lidocaine was used as a standardized experimental pain stimulus. Pain was evaluated using a visual analog scale (VAS 1: infiltration in the hand, and VAS 2: infiltration in the procedure area)

Results

Scores on the PSQ-T were significantly correlated with those on the BPI-SF. A significant positive relationship was observed between VAS 1 and VAS 2 values and the PSQ-T score, BPI pain score, and BPI interference score.

Conclusions

The PSQ-T can be used as a valid and reliable tool for the assessment of pain sensitivity in the Turkish population.

The Effects of Gender, Functional Condition, and ADL on Pressure Pain Threshold in Stroke Patients

Background

Somatosensory impairments and pain are common symptoms following stroke. However, the condition of perception and pain threshold for pressure stimuli and the factors that can influence this in individuals with stroke are still unclear. This study aimed to investigate the gender differences in pressure pain threshold (PPT) and positive somatosensory signs for pressure stimuli, and explore the effects of joint pain, motor function, and activities of daily living (ADL) on pain threshold in post-stroke patients.

Design

A cross-sectional study.

Methods

A total of 60 participants with stroke were recruited, and their pain condition, motor functions, and ADL were evaluated by the Fugl-Meyer assessment of joint pain scale, motor function scale, and Barthel index, respectively. PPTs in eight tested points at the affected and unaffected sides were assessed.

Results

Significant differences in PPTs were found between male and female patients in all measured muscles (p < 0.05). Positive somatosensory signs for pressure stimuli, including hypoalgesia and hyperalgesia, were frequently found at the affected side, particularly in the extremity muscles, but such signs were not significantly influenced by gender (p > 0.05). More equal PPTs between both sides and relatively lower PPTs at the affected side in the trunk and medial gastrocnemius muscles (p < 0.05) were observed in patients with less pain, better motor functions, and ADL.

Conclusion

Gender differences widely exist in post-stroke survivors either at the affected or unaffected side, which are multifactorial. Sensory loss and central and/or peripheral sensitization, such as hypoalgesia and hyperalgesia for pressure stimuli, caused by a brain lesion are common signs in male and female stroke patients. Moreover, patients who are in a better condition show a more symmetrical pain sensitivity between both sides in the trunk and in female lower extremities, indicating the bidirectional improvement of somatosensory abnormalities caused by a possible neural plasticity.

Patient phenotyping in clinical trials of chronic pain treatments: IMMPACT recommendations

There is tremendous interpatient variability in the response to analgesic therapy (even for efficacious treatments), which can be the source of great frustration in clinical practice. This has led to calls for “precision medicine” or personalized pain therapeutics (ie, empirically based algorithms that determine the optimal treatments, or treatment combinations, for individual patients) that would presumably improve both the clinical care of patients with pain and the success rates for putative analgesic drugs in phase 2 and 3 clinical trials. However, before implementing this approach, the characteristics of individual patients or subgroups of patients that increase or decrease the response to a specific treatment need to be identified. The challenge is to identify the measurable phenotypic characteristics of patients that are most predictive of individual variation in analgesic treatment outcomes, and the measurement tools that are best suited to evaluate these characteristics. In this article, we present evidence on the most promising of these phenotypic characteristics for use in future research, including psychosocial factors, symptom characteristics, sleep patterns, responses to noxious stimulation, endogenous pain-modulatory processes, and response to pharmacologic challenge. We provide evidence-based recommendations for core phenotyping domains and recommend measures of each domain.

Translation, Cross-Cultural Adaptation, and Validation of the Pain Sensitivity Questionnaire in Dutch Healthy Volunteers

An increased sensitivity to painful stimuli has been proposed to be related to the development of chronic pain. Therefore, assessment of individual pain sensitivity is useful in clinical practice. However, experimental pain testing may be uncomfortable for patients and requires specific equipment. The Pain Sensitivity Questionnaire (PSQ) has been developed to facilitate assessment of pain sensitivity. In this study, we aimed to translate and cross-culturally adapt the PSQ from its published German and English versions into the Dutch language and to assess validity of the PSQ in healthy volunteers. After translation and cross-cultural adaptation of the PSQ following international guidelines, we validated the PSQ in 394 healthy volunteers by comparing the PSQ-values with two different experimental pain tests: electrical pain tolerance (EPT) and pressure pain threshold (PPT). In addition, ratings of pain intensity during these tests were obtained on the numerical rating scale (NRS, 0-10). We found that the reliability of the PSQ based on internal consistency was good (Cronbach's alpha 0.90). PSQ-scores, adjusted for age and sex, were statistically significant and weakly inversely correlated to EPT (PSQ-moderate: rho = -0.24, p=0.007; PSQ-total: rho = -0.22, p=0.016). No statistically significant correlation between PSQ-scores and PPT was found. Concerning the pain scores, PSQ-scores were weakly to moderately correlated to EPT-NRS (PSQ-minor: rho = 0.21, p=0.021; PSQ-moderate: rho = 0.22, p=0.016; PSQ-total: rho = 0.23, p=0.009) as well as PPT-NRS (PSQ-minor: rho = 0.32, p < 0.001; PSQ-moderate: rho = 0.36, p < 0.001; PSQ-total: rho = 0.37, p < 0.001). Therefore, we concluded that the Dutch version of the PSQ is culturally appropriate for assessing self-reported pain sensitivity in healthy volunteers.

Pressure Pain Tolerance Predicts the Success of Emotional Awareness and Expression Therapy in Patients With Fibromyalgia

OBJECTIVES

Quantitative sensory testing may help predict treatment responses in individuals with chronic pain. Our objective was to determine whether evoked pain sensitivity at baseline predicted preferential treatment responses to either emotional awareness and expression therapy (EAET) or cognitive behavioral therapy (CBT) in individuals with fibromyalgia (FM).

METHODS

This was a secondary analysis of a previous randomized clinical trial, in which individuals with FM were randomized to EAET, CBT, or Education as a control intervention. Only females who completed baseline and post-treatment assessments were analyzed (n=196). The primary outcome was change in overall clinical pain severity from pretreatment to posttreatment, and the primary predictor of interest was pressure pain tolerance at baseline.

RESULTS

Among patients with low pain tolerance at baseline (n=154), both EAET and CBT led to small but significant improvements in clinical pain severity (CBT mean=0.66, 95% confidence interval [0.24-1.07]; EAET mean=0.76 [0.34-1.17]). Conversely, in patients with normal pain tolerance (n=42), there was no significant improvement in clinical pain after CBT (0.13 [-0.88 to 1.14]), a small improvement after FM Education (0.81 [0.14-1.48]), but a much larger and statistically significant improvement after EAET (2.14 [1.23-3.04]).

DISCUSSION

Normal levels of pressure pain tolerance at baseline predicted greater improvement in clinical pain severity after EAET than CBT. Quantitative sensory testing may provide insights about individual responses to psychologically based therapies for individuals with chronic pain.

An Evaluation of Sex Differences in Patients With Chronic Pain Undergoing an Interdisciplinary Pain Treatment Program

OBJECTIVES

To determine if there are sex differences in a sample of patients participating in a 4-week interdisciplinary pain treatment program in (1) pretreatment pain intensity, physical function, psychological function, pain beliefs, kinesiophobia, pain catastrophizing, and activity management patterns; and (2) treatment response.

METHODS

Seventy-two men and 130 women with chronic pain completed study measures. Analyses of covariance (ANCOVAs) were performed to compare men and women on pretreatment measures. Repeated-measures ANCOVAs were used to compare both sexes on 3 treatment outcomes (pain intensity, physical function, and depressive symptoms).

RESULTS

Before treatment, compared to women, men reported higher levels of kinesiophobia, were more likely to view their pain as being harmful, and used more activity pacing when doing daily activities. Women were more likely to use an overdoing activity pattern than men. No sex differences emerged for pretreatment pain intensity, physical function, psychological function, catastrophizing, activity avoidance, or measures of other pain-related beliefs. At posttreatment, women reported more improvements in pain intensity and physical function compared to men, while both sexes reported similar reductions in depressive symptoms. All effect sizes for statistically significant findings were of small to moderate magnitude.

DISCUSSION

The results of this study suggest that men and women have a comparable profile with respect to the overall burden of chronic pain. Nevertheless, sex differences were found for certain pain beliefs and coping styles. Women appear to reap more benefits from the interdisciplinary pain management program than men. These findings indicate that further research to develop sex-specific assessment procedures and tailored pain treatments may be warranted.

The LURN Research Network Neuroimaging and Sensory Testing (NIST) Study: Design, protocols, and operations

The Neuroimaging and Sensory Testing (NIST) Study of the Symptoms of Lower Urinary Tract Dysfunction Research Network (LURN) is a cross-sectional, case-control study designed to investigate whether disrupted brain connectivity and sensory processing are associated with abnormal lower urinary tract symptoms (LUTS) in patients with overactive bladder syndrome (OAB). The NIST Study tests the hypotheses that patients with urinary urgency will demonstrate: (1) abnormal functional and structural connectivity of brain regions involved in urinary sensation on magnetic resonance imaging (MRI), and (2) hypersensitivity to painful (pressure) and non-painful (auditory) sensory stimuli on quantitative sensory testing (QST), compared to controls. Male and female adults (18 years or older) who present at one of the six participating LURN clinical centers for clinical care of their LUTS, with symptoms of urinary urgency with or without urgency urinary incontinence, are eligible to participate. The NIST Study is the largest MRI and QST study of its kind, yielding a neuroimaging and sensory testing dataset unprecedented in OAB research. Advanced multi-modal techniques are used to understand brain functional and structural connectivity, including gray matter volume, and sensory function. Unlike previous MRI studies which involved invasive catheterization and repeated cycles of non-physiologic bladder filling and emptying via a catheter, we use a water ingestion protocol to mimic more physiological bladder filling through natural diuresis. Furthermore, these data will be used in concert with other phenotyping data to improve our understanding of clinically meaningful subtypes of patients with LUTS in order to improve patient care and management outcomes.

Single Nucleotide Polymorphism in the COL11A2 Gene Associated with Heat Pain Sensitivity in Knee Osteoarthritis

Pain is one of the most prominent symptoms of osteoarthritis. However, there is often discordance between the pain experienced by individuals with osteoarthritis and the degree of articular pathology. This suggests that individual differences, including genetic variability in the central processing of nociceptive stimuli, may impact the presentation of osteoarthritis. Here, we show that the single nucleotide polymorphism rs16868943 in the collagen gene COL11A2 is significantly associated with lowered heat pain tolerance on the arm in participants with knee osteoarthritis (P = 1.21 × 10⁻⁶, P = 0.0053 after Bonferroni correction, beta = −3.42). A total of 161 knee osteoarthritis participants were included and evaluated for heat, punctate and pressure pain sensitivity of the affected knee and the ipsilateral arm. Each participant was genotyped for 4392 single nucleotide polymorphisms in genes implicated in pain perception, inflammation and mood and tested for association with pain sensitivity. The minor A allele of single nucleotide polymorphism rs16868943 was significantly associated with lower arm heat pain tolerance after correction for age, gender, race, and study site. This single nucleotide polymorphism was also nominally associated with other measures of heat pain sensitivity, including lowered knee heat pain tolerance (P = 1.14 × 10⁻⁵, P = 0.05 after Bonferroni correction), lowered arm heat pain threshold (P = 0.0039, uncorrected) and lowered knee heat pain threshold (P = 0.003, uncorrected). Addition of genotypes from 91 participants without knee pain produced a significant interaction between knee osteoarthritis status and the rs16868943 single nucleotide polymorphism in heat pain tolerance (P = 1.71 × 10⁻⁵), such that rs16868943 was not associated with heat pain tolerance in participants without knee pain (P = 0.12, beta = 1.3). This is the first study to show genetic association with heat pain tolerance in individuals with osteoarthritis. The association is specific to participants who have already developed knee osteoarthritis, suggesting that the COL11A2 gene, which has previously been associated with familial osteoarthritis, may play a role in pain sensitization after the development of osteoarthritis.

Validation of the Norwegian Pain Sensitivity Questionnaire

Background and purpose

There is a large variation in people’s reactions to painful stimuli. Although some conditions are more painful, the variation between people is larger than the reaction to pain across conditions. Induced experimental pain is one way to assess some aspects of these differences in pain perception. Experimental nociceptive testing is time consuming and not always feasible in a clinical setting. In order to overcome the obstacles of assessing pain sensitivity using experimental stimulation, the Pain Sensitivity Questionnaire (PSQ) was developed. The purpose of this study is to validate the Norwegian version of the PSQ.

Methods

Construct validity was examined through an exploratory principal component factor analysis with varimax rotation. Internal consistency was measured by Cronbach’s alpha reliability for subscales and the total PSQ. As confounding variables such as age and gender may contribute to the experience of pain, a regression analysis was performed with demographic variables and PSQ scores as independent variables and the experimental measures of pain as the dependent variable.

Results

The factor analysis yielded at two factor solution, with an eigenvalue greater than one, explain 58% of the variance. Cronbach’s alpha for the PSQ was 0.92. In the regression analysis, only PSQ scores contributed to explain the experimental pain intensity and tolerance. Gender only influenced the experimental pain threshold, as men had statistically significant higher heat pain threshold than women.

Conclusion

This study shows that PSQ is a valid and reliable questionnaire and might be a promising instrument for assessing pain sensitivity in Norwegian clinical settings. Further studies are needed to examine whether the PSQ can be used in clinical settings to predict postoperative pain and the development of chronic pain.

Chronic pain and sex-differences; women accept and move, while men feel blue

Purpose

The aim of this study is to explore differences between male and female patients entering a rehabilitation program at a pain clinic in order to gain a greater understanding of different approaches to be used in rehabilitation.

Method

1371 patients referred to a specialty pain rehabilitation clinic, completed sociodemographic and pain related questionnaires. They rated their pain acceptance (CPAQ-8), their kinesiophobia (TSK), the impact of pain in their life (MPI), anxiety and depression levels (HAD) and quality of life scales: the SF-36, LiSat-11, and the EQ-5D. Because of the large sample size of the study, the significance level was set at the p ≤.01.

Results

Analysis by t-test showed that when both sexes experience the same pain severity, women report significantly higher activity level, pain acceptance and social support while men report higher kinesiophobia, mood disturbances and lower activity level.

Conclusion

Pain acceptance (CPAQ-8) and kinesiophobia (TSK) showed the clearest differences between men and women. Pain acceptance and kinesiophobia are behaviorally defined and have the potential to be changed.

Patient phenotyping in clinical trials of chronic pain treatments: IMMPACT recommendations

There is tremendous interpatient variability in the response to analgesic therapy (even for efficacious treatments), which can be the source of great frustration in clinical practice. This has led to calls for "precision medicine" or personalized pain therapeutics (ie, empirically based algorithms that determine the optimal treatments, or treatment combinations, for individual patients) that would presumably improve both the clinical care of patients with pain and the success rates for putative analgesic drugs in phase 2 and 3 clinical trials. However, before implementing this approach, the characteristics of individual patients or subgroups of patients that increase or decrease the response to a specific treatment need to be identified. The challenge is to identify the measurable phenotypic characteristics of patients that are most predictive of individual variation in analgesic treatment outcomes, and the measurement tools that are best suited to evaluate these characteristics. In this article, we present evidence on the most promising of these phenotypic characteristics for use in future research, including psychosocial factors, symptom characteristics, sleep patterns, responses to noxious stimulation, endogenous pain-modulatory processes, and response to pharmacologic challenge. We provide evidence-based recommendations for core phenotyping domains and recommend measures of each domain.

Effects of a Hypnotic Induction and an Unpleasantness-Focused Analgesia Suggestion on Pain Catastrophizing to an Experimental Heat Stimulus: A Preliminary Study

Pain catastrophizing is associated with greater levels of pain. While many studies support the efficacy of hypnosis for pain, the effect on pain catastrophizing remains unclear. The present study evaluated the effect of hypnosis on pain catastrophizing using experimental heat stimulation. Twenty-two pain patients engaged in 3 conditions: baseline (no suggestion), hypnotic induction, and hypnotic induction plus analgesia suggestion. Participants with higher baseline pain showed a significant reduction in rumination following hypnotic induction plus analgesia suggestion and significant reductions in pain due to both the hypnotic induction alone and the hypnotic induction plus analgesia suggestion. The findings suggest that unpleasantness-focused hypnotic analgesia reduces pain via its effect on the rumination component of pain catastrophizing.

Minority Aging and Endogenous Pain Facilitatory Processes

OBJECTIVE

The aim of the current study was to examine the relationships among age, ethnicity, and endogenous pain facilitation using temporal summation (TS) responses to mechanical and heat stimuli.

DESIGN

The present study assessed hyperalgesia and pain facilitation to thermal and mechanical stimuli at the knee and distal sites in 98 pain-free men and women. Participants were drawn from two ethnic groups [African-American (AA) and non-Hispanic white (NHW)] and two age groups (19-35 and 45-85).

RESULTS

Significant main effects of ethnicity were demonstrated for both mechanical and heat modalities (all P's ≤ 0.05), suggesting that AA participants, relative to NHW counterparts, demonstrated enhanced hyperalgesia. Age differences (older > younger) in hyperalgesia were found in mechanical pain ratings only. Results indicated that mechanical pain ratings significantly increased from first to maximal pain as a function of both age group and ethnicity (all P's ≤ 0.05), and a significant ethnicity by age interaction for TS of mechanical pain was found at the forearm (P < 0.05) and trended toward significance at the knee (P = 0.071). Post-hoc tests suggested that results were primarily driven by the older AA participants, who demonstrated the greatest mechanical TS. Additionally, evidence of differences in heat TS due to both ethnicity alone (all P's ≤ 0.05) and minority aging was also found.

CONCLUSIONS

This study provides evidence suggesting that older AAs demonstrate enhanced pain facilitatory processes, which is important because this group may be at increased risk for development of chronic pain. These results underscore the necessity of testing pain modulatory mechanisms when addressing questions related to pain perception and minority aging.

Chronic Back Pain Is Associated with Alterations in Dopamine Neurotransmission in the Ventral Striatum

Back pain is common in the general population, but only a subgroup of back pain patients develops a disabling chronic pain state. The reasons for this are incompletely understood, but recent evidence implies that both preexisting and pain-related variations in the structure and function of the nervous system may contribute significantly to the development of chronic pain. Here, we addressed the role of striatal dopamine (DA) D2/D3 receptor (D2/D3R) function in chronic non-neuropathic back pain (CNBP) by comparing CNBP patients and healthy controls using PET and the D2/D3R-selective radioligand [(11)C]raclopride. D2/D3R availability was measured at baseline and during a pain challenge, yielding in vivo measures of receptor availability (binding potential, BPND) and DA release (change in BPND from baseline to activated state). At baseline, CNBP patients demonstrated reductions in D2/D3R BPND in the ventral striatum compared with controls. These reductions were associated with greater positive affect scores and pain tolerance measures. The reductions in D2/D3R BPND were also correlated with μ-opioid receptor BPND and pain-induced endogenous opioid system activation in the amygdala, further associated with measures of positive affect, the affective component of back pain and pain tolerance. During the pain challenge, lower magnitudes of DA release, and therefore D2/D3R activation, were also found in the ventral striatum in the CNBP sample compared with controls. Our results show that CNBP is associated with adaptations in ventral striatal D2/D3R function, which, together with endogenous opioid system function, contribute to the sensory and affective-motivational features of CNBP.

SIGNIFICANCE STATEMENT

The neural systems that underlie chronic pain remain poorly understood. Here, using PET, we provide insight into the molecular mechanisms that regulate sensory and affective dimensions of pain in chronic back pain patients. We found that patients with back pain have alterations in brain dopamine function that are associated with measures of pain sensitivity and affective state, but also with brain endogenous opioid system functional measures. These findings suggest that brain dopamine-opioid interactions are involved in the pathophysiology of chronic pain, which has potential therapeutic implications. Our results may also help to explain individual variation in susceptibility to opioid medication misuse and eventual addiction in the context of chronic pain.

Sex differences in experimental measures of pain sensitivity and endogenous pain inhibition

It has been suggested that increased pain sensitivity and disruption of endogenous pain inhibitory processes may account, at least in part, for the greater prevalence and severity of chronic pain in women compared to men. However, previous studies addressing this topic have produced mixed findings. This study examined sex differences in pain sensitivity and inhibition using quantitative sensory testing (QST), while also considering the influence of other important factors such as depressive symptoms and sleep quality. Healthy men (n=24) and women (n=24) each completed a QST battery. This battery included an ischemic pain task (IPT) that used a submaximal effort tourniquet procedure as well as a conditioned pain modulation (CPM) procedure for the assessment of endogenous pain inhibition. Prior to QST, participants completed the Center for Epidemiologic Studies Depression Scale and the Pittsburgh Sleep Quality Index. Analyses revealed significant sex differences for the ischemic pain task and the conditioned pain modulation procedure, such that women tolerated the ischemic pain for a shorter amount of time and demonstrated less pain inhibition compared with men. This remained true even when accounting for sex differences in depressive symptoms and sleep quality. The results of this study suggest that women may be more pain sensitive and possess less-efficient endogenous pain inhibitory capacity compared with men. Whether interventions that decrease pain sensitivity and enhance pain inhibition in women ultimately improve their clinical pain outcomes is an area of research that deserves additional attention in the future.

Do fibromyalgia patients benefit from cognitive restructuring and acceptance? An experimental study

BACKGROUND AND OBJECTIVES

The aim of this study was to clarify mechanisms of psychological fibromyalgia treatment by experimentally examining the effectiveness of its core elements. We assessed the effects of cognitive restructuring and acceptance on experimentally-induced heat and cold pain tolerance and pain intensity in fibromyalgia patients.

METHODS

Cold and heat pain were induced in a sample of 60 fibromyalgia patients using a thermode. We conducted ANCOVAs to examine group differences in posttest scores, co-varying for pretest scores. The between-groups factor was the type of instruction provided (acceptance, cognitive restructuring, and a control condition). In addition, we controlled for pain sensitivity, age, and depression.

RESULTS

We found that acceptance and cognitive restructuring were superior to the control condition in increasing heat pain tolerance, but did not differ from one another. With respect to cold pain tolerance, cognitive restructuring was associated with increases in cold pain tolerance compared to the control condition, while acceptance did not differ either from the control condition or from cognitive restructuring.

LIMITATIONS

Further experimental research on chronic pain treatment mechanisms is needed, particularly research on individually tailoring treatment strategies according to patients characteristics.

CONCLUSION

Results show that both, cognitive restructuring and acceptance instructions, enhance pain tolerance in fibromyalgia patients.

Fear of severe pain mediates sex differences in pain sensitivity responses to thermal stimuli

The purpose of this paper was to examine the relationship of sex and pain-related fear in pain intensity reports to thermal stimuli and whether sex differences in reported pain intensity were mediated by pain-related fear. 177 participants, 124 female (23.5 ± 4.5 years old), filled out a demographic and fear of pain questionnaire (FPQ-III). Experimental pain testing was performed using thermal stimuli applied to the lower extremity. Participants rated the intensity of pain using the numerical pain rating scale (NPRS). Independent t-tests, Sobel's test, and linear regression models were performed to examine the relationships between sex, fear of pain, and pain sensitivity. We found significant sex differences for thermal pain threshold temperatures (t = 2.04,  P = 0.04) and suprathreshold pain ratings for 49°C (t = -2.12,  P = 0.04) and 51°C (t = -2.36,  P = 0.02). FPQ-severe score mediated the effect of suprathreshold pain ratings of 49° (t = 2.00,  P = 0.05), 51° (t = 2.07,  P = 0.04), and pain threshold temperatures (t = -2.12,  P = 0.03). There are differences in the pain sensitivity between sexes, but this difference may be mediated by baseline psychosocial factors such as fear of pain.

Chronic pain epidemiology - where do lifestyle factors fit in?

Chronic pain is common and complex and has a large impact on individuals and society. Good epidemiological pain data provide key information on the use of resources (both in general practice and in specialist clinics), insight into factors that lead to or favour chronicity and the design of interventions aimed at reducing or preventing the effects of chronic pain. This review aims to highlight the important factors associated with chronic pain, including those factors which are amenable to lifestyle intervention.

Psychological screening/phenotyping as predictors for spinal cord stimulation

Spinal cord stimulation (SCS) is becoming a widely used treatment for a number of pain conditions and is frequently considered as a pain management option when conservative or less invasive techniques have proven to be ineffective. Potential indications for SCS include complex regional pain syndrome (CRPS), postherpetic neuralgia, traumatic nerve injury, failed back surgery syndrome, refractory angina pectoris, peripheral vascular disease, neuropathic pain, and visceral pain (Guttman et al. Pain Pract. 9:308-11, 2009). While research on SCS is in its infancy, it is clear that substantial variation exists in the degree of benefit obtained from SCS, and the procedure does not come without risks; thus focused patient selection is becoming very important. Psychological characteristics play an important role in shaping individual differences in the pain experience and may influence responses to SCS, as well as a variety of other pain treatments (Doleys Neurosurg Focus 21:E1, 2006). In addition to psychological assessment, quantitative sensory testing (QST) procedures offer another valuable resource in forecasting who may benefit most from SCS and may also shed light on mechanisms underlying the individual characteristics promoting the effectiveness of such procedures (Eisenberg et al. Pain Pract. 6:161-165, 2006). Here, we present a brief overview of recent studies examining these factors in their relationship with SCS outcomes.

A simple cold pressure technique for the evaluation of analgesic drugs in healthy subjects

Aim:

An experimental pain model which is sensitive and reproducible would be a useful pharmacological tool both for existing and new drugs. The aim of the present study was to establish a simple and reliable method of producing experimental pain which can be used for screening of analgesic agents.

Materials and Methods:

The method was standardized by recording pain threshold and pain tolerance values in 24 healthy volunteers. Reproducibility of the test procedure was evaluated by recording the pain threshold and pain tolerance values by a single observer on two sessions (inter-day reproducibility), and second observer in one session (inter-observer reproducibility), separately. Validity of the model was further tested by evaluating the analgesic effect of tramadol in 12 healthy volunteers.

Results:

Cold pain model was found to produce low variability with coefficient of variation less than 15%. Inter-observer and inter-day reproducibility was very good as shown by Bland – Altman plot with most of the values within ± 2SD. Analgesic activity by Tramadol was statistically different from placebo (P < 0.05).

Conclusion:

The newly developed pain model offers a stable and sensitive method for the early assessment of analgesic activity.

Role of environmental factors and history of low back pain in sciatica symptoms among Finnish adolescents

STUDY DESIGN

Cross-sectional study in a subcohort of the 1986 Northern Finland Birth Cohort (n = 1987).

OBJECTIVE

To investigate the role of environmental factors and LBP history in sciatica symptoms among Finnish young adults.

SUMMARY OF BACKGROUND DATA

History of low back pain (LBP), smoking, and male sex are associated with sciatica in adult populations. The role of the environmental determinants of sciatica has not been evaluated in populations consisting of only adolescents.

METHODS

Sciatic symptoms and environmental exposures were elicited by a mailed questionnaire and the associations were analyzed using multinomial logistic regression.

RESULTS

Female sex was associated with severe sciatica at 18 years (OR, 3.9; 95% confidence interval (CI), 1.6-9.3). Both reported LBP at 16 years and LBP requiring consultation of a health care professional were associated with mild sciatica at 18 years (OR, 2.5; 95% CI, 1.3-4.9; and OR, 3.8; 95% CI, 1.2-11.9). In addition, LBP at 16 years requiring consultation of a health care professional was associated with severe sciatica at 18 years (OR, 5.0; 95% CI, 1.7-15.3). Smoking, obesity, physical workload, and level of physical activity were not associated with sciatica.

CONCLUSION

Females reported sciatic pain more often than males. LBP at 16 years predicted sciatica at 18 years.

LEVEL OF EVIDENCE

2.

Effect of sedation on pain perception

BACKGROUND

Sedation or anesthesia is used to facilitate many cases of an estimated 45 million diagnostic and therapeutic medical procedures in the United States. Preclinical studies have called attention to the possibility that sedative-hypnotic drugs can increase pain perception, but whether this observation holds true in humans and whether pain-modulating effects are agent-specific or characteristic of IV sedation in general remain unclear.

METHODS

To study this important clinical question, the authors recruited 86 healthy volunteers and randomly assigned them to receive one of three sedative drugs: midazolam, propofol, or dexmedetomidine. The authors asked participants to rate their pain in response to four experimental pain tasks (i.e., cold, heat, ischemic, or electrical pain) before and during moderate sedation.

RESULTS

Midazolam increased cold, heat, and electrical pain perception significantly (10-point pain rating scale change, 0.82 ± 0.29, mean ± SEM). Propofol reduced ischemic pain and dexmedetomidine reduced both cold and ischemic pain significantly (-1.58 ± 0.28, mean ± SEM). The authors observed a gender-by-race interaction for dexmedetomidine. In addition to these drug-specific effects, the authors observed gender effects on pain perception; female subjects rated identical experimental pain stimuli higher than male subjects. The authors also noted race-drug interaction effects for dexmedetomidine, with higher doses of drug needed to sedate Caucasians compared with African Americans.

CONCLUSIONS

The results of the authors' study call attention to the fact that IV sedatives may increase pain perception. The effect of sedation on pain perception is agent- and pain type-specific. Knowledge of these effects provides a rational basis for analgesia and sedation to facilitate medical procedures.

Quantitative changes in regional cerebral blood flow induced by cold, heat and ischemic pain: a continuous arterial spin labeling study

BACKGROUND

The development of arterial spin labeling methods has allowed measuring regional cerebral blood flow (rCBF) quantitatively and to show the pattern of cerebral activity associated with any state such as a sustained pain state or changes due to a neurotropic drug.

METHODS

The authors studied the differential effects of three pain conditions in 10 healthy subjects on a 3 Tesla scanner during resting baseline, heat, cold, and ischemic pain using continuous arterial spin labeling.

RESULTS

Cold pain showed the greatest absolute rCBF increases in left anterior cingulate cortex, left amygdala, left angular gyrus, and Brodmann area 6, and a significant rCBF decrease in the cerebellum. Changes in rCBF were characteristic of the type of pain condition: cold and heat pain showed increases, whereas the ischemic condition showed a reduction in mean absolute gray matter flow compared with rest. An association of subjects' pain tolerance and cerebral blood flow was noted.

CONCLUSIONS

The observation that quantitative rCBF changes are characteristic of the pain task used and that there is a consistent rCBF change in Brodman area 6, an area responsible for the integration of a motor response to pain, should provide extremely useful information in the quest to develop an imaging biomarker of pain. Conceivably, response in BA6 may serve as an objective measure of analgesic efficacy.

Validation of the pain sensitivity questionnaire in chronic pain patients

Recently, a self-rating measure for pain perception based on imagined painful daily life situations, the Pain Sensitivity Questionnaire (PSQ), has been developed and shown to correlate with experimentally obtained pain intensity ratings in healthy subjects. Here, we assessed the validity of the PSQ for investigation of general pain perception (ie, pain perception outside the site of clinical pain) in chronic pain patients. PSQ scores were obtained in 134 chronic pain patients and compared to those of 185 healthy control subjects. In a subgroup of 46 chronic pain patients, we performed experimental pain testing outside the clinical pain site, including different modalities (heat, cold, pressure, and pinprick) and different measures (pain thresholds, pain intensity ratings). Results show that PSQ scores were significantly correlated with both experimental pain intensity ratings (Pearson's r=0.71, P<.001) and experimental pain thresholds (r=-0.52, P<.001). In addition, chronic pain patients exhibited significantly elevated PSQ scores as compared to healthy controls, consistent with the generalized increase of experimentally determined pain perception that has repeatedly been reported in chronic pain patients. These results demonstrate that the PSQ constitutes a valid self-rating measure of pain perception outside the clinical pain site in chronic pain patients and might serve as an alternative to experimental assessment of pain perception outside the clinical pain site in situations where experimental pain testing is not feasible.

Elevated pain sensitivity in chronic pain patients at risk for opioid misuse

This study employed quantitative sensory testing (QST) to evaluate pain responses in chronic spinal pain patients at low risk and high risk for opioid misuse, with risk classification based on scores on the Screener and Opioid Assessment for Patients with Pain-Revised (SOAPP-R). Patients were further subgrouped according to current use of prescription opioids. Of the 276 chronic pain patients tested, approximately 65% were taking opioids; a median split was used to further categorize these patients as being on lower or higher doses of opioids. The high-risk group (n = 161) reported higher levels of clinical pain, had lower pressure and thermal pain thresholds at multiple body sites, had lower heat pain tolerance, and rated repetitive mechanical stimuli as more painful relative to the low-risk group (n = 115; P's < .01). In contrast, QST measures did not differ across opioid groups. Multiple linear regression analysis suggested that indices of pain-related distress (ie, anxiety and catastrophizing about pain) were also predictive of hyperalgesia, particularly in patients taking opioids. Collectively, regardless of opioid status, the high-risk group was hyperalgesic relative to the low-risk group; future opioid treatment studies may benefit from the classification of opioid risk, and the examination of pain sensitivity and other factors that differentiate high- and low-risk groups.

PERSPECTIVE

This study demonstrates that chronic spinal pain patients at high risk for misuse of prescription opioids are more pain-sensitive than low-risk patients, whether or not they are currently taking opioids. Indices of pain-related distress were important predictors of pain sensitivity, particularly among those patients taking opioids for pain.

Ethnic Group Differences in the Outcomes of Multidisciplinary Pain Treatment

OBJECTIVES: The aim of this prospective investigation was to evaluate ethnic group differences in pain-related outcomes following multidisciplinary chronic pain treatment. A prospective pre- and post-treatment assessment design was employed to investigate the effects of ethnicity on changes in pain-related variables following completion of a multidisciplinary pain treatment program. METHODS: One hundred fifty five chronic pain patients participating in a multidisciplinary pain treatment program completed measures of pain and mood both prior to and following the four-week treatment. Primary outcome variables included pain severity, pain-related interference, and depressive symptoms. RESULTS: Baseline differences between African-Americans and Whites were observed for depressive symptoms, but not for pain severity or pain-related interference. Following multidisciplinary pain treatment, both White and African-American patients displayed post-treatment reductions in depressive symptoms and pain-related interference. However, White patients also reported reduced pain severity while African-Americans did not. CONCLUSIONS: The treatment approach used in the present study appeared to be less effective in reducing self-reported pain severity in African-American versus White patients, though both groups benefited in terms of reduced depressive symptoms and pain-related interference. Moreover, the observation that improvements in functioning occurred without reductions in pain severity in African-American patients suggests that differences may exist in treatment processes as a function of ethnic group, and will consequently be an important area for future research.

Substance misuse treatment for high-risk chronic pain patients on opioid therapy: a randomized trial

Chronic pain patients who show aberrant drug-related behavior often are discontinued from treatment when they are noncompliant with their use of opioids for pain. The purpose of this study was to conduct a randomized trial in patients who were prescribed opioids for noncancer back pain and who showed risk potential for or demonstration of opioid misuse to see if close monitoring and cognitive behavioral substance misuse counseling could increase overall compliance with opioids. Forty-two patients meeting criteria for high-risk for opioid misuse were randomized to either standard control (High-Risk Control; N=21) or experimental compliance treatment consisting of monthly urine screens, compliance checklists, and individual and group motivational counseling (High-Risk Experimental; N=21). Twenty patients who met criteria indicating low potential for misuse were recruited to a low-risk control group (Low-Risk Control). Patients were followed for 6 months and completed pre- and post-study questionnaires and monthly electronic diaries. Outcomes consisted of the percent with a positive Drug Misuse Index (DMI), which was a composite score of self-reported drug misuse (Prescription Drug Use Questionnaire), physician-reported abuse behavior (Addiction Behavior Checklist), and abnormal urine toxicology results. Significant differences were found between groups with 73.7% of the High-Risk Control patients demonstrating positive scores on the DMI compared with 26.3% from the High-Risk Experimental group and 25.0% from the Low-Risk Controls (p<0.05). The results of this study demonstrate support for the benefits of a brief behavioral intervention in the management of opioid compliance among chronic back pain patient at high-risk for prescription opioid misuse.

Sex differences in experimental and clinical pain sensitivity for patients with shoulder pain

Previous research demonstrates that men and women differ in the way that they perceive and process pain. Much of this work has been done in healthy adults with a lack of consensus in clinical pain populations. The purpose of this study was to investigate how men and women with shoulder pain differ in their experience of experimental and clinical pain and whether psychological processes differentially affect these responses. Fifty-nine consecutive subjects (24 women, 35 men) seeking operative treatment for shoulder pain were enrolled in this study. Subjects completed self report questionnaires to assess clinical pain, catastrophizing, anxiety and depression and underwent a series of experimental pain tests consisting of pressure pain, thermal pain (threshold and tolerance), and thermal temporal summation. Results indicated that women experienced greater clinical pain and enhanced sensitivity to pressure pain. Age did not affect the observed sex differences. There were no sex differences in psychological association with experimental and clinical pain in this cohort. The relationship between clinical and experimental pressure pain was stronger in women as compared to men. These findings offer insight into the interactions between biological and psychosocial influences of pain and how these interactions vary by sex.