Optimizing Pain Intensity Assessment in Clinical Trials: How Many Ratings are Needed to Best Balance the Need for Validity and to Minimize Assessment Burden?

Pain intensity is the most commonly used outcome domain in pain clinical trials. To minimize the chances of type II error (ie, concluding that a treatment does not have beneficial effects, when in fact it does), the measure of pain intensity used should be sensitive to changes produced by effective pain treatments. Here we sought to identify the combination of pain intensity ratings that would balance the need for reliability and validity against the need to minimize assessment burden. We conducted secondary analyses using data from a completed 4-arm clinical trial of psychological pain treatments (N = 164 adults). Current, worst, least, and average pain intensity in the past 24 hours were assessed 4 times before and after treatment using 0 to 10 numerical rating scale-11. We created a variety of composite scores using these ratings and evaluated their reliability (Cronbach's alphas) and validity (ie, associations with a gold standard score created by averaging 16 ratings and sensitivity for detecting between-group differences in treatment efficacy). We found that for each measure, reliability increased as the number of ratings used to create the measures increased and that ratings from 3 or more days were needed to have adequately strong associations with the gold standard. Regarding sensitivity, the findings suggest that composite scores made up of ratings from 4 days are needed to maximize the chances of detecting treatment effects, especially with smaller sample sizes. In conclusion, using data from 3 or 4 days of assessment may be the best practice. PERSPECTIVE: Composite scores made up of at least 3 days of pain ratings appear to be needed to maximize reliability and validity while minimizing the assessment burden. TRIAL REGISTRATION: clinicaltrials.gov NCT01800604.

Perceived Stress, Perceived Social Support, and Global Health in Adults with Chronic Pain.

BACKGROUND: Chronic pain is a common problem in adults that can have a significant impact on individuals' quality of life and on society. The complex pain experience emerges from a dynamic combination of biological, psychological, and social factors. Previous research has shown that social support has positive effects on health-related outcomes through two mechanisms: direct-effects and stress-buffering effects. The aim of this study was to investigate the role that perceived stress, perceived social support, and their interaction play as predictors of global physical health and global mental health in adults with chronic pain. METHOD: One hundred sixty-five adults with chronic pain completed measures of pain, perceived stress, perceived social support, global physical health, and global mental health. RESULTS: Perceived stress but not perceived social support made a significant and independent contribution to the prediction of global physical health; both perceived stress and perceived social support made independent contributions to the prediction of global mental health. The perceived stress × perceived social support interaction did not make a significant contribution to the prediction of either criterion variable. The results suggested that perceived stress has an impact on both global physical and mental health, whereas perceived social support associated mostly with global mental health. In addition, perceived social support does not appear to moderate the impact of stress on global physical and mental health. CONCLUSION: The findings are more consistent with a direct-effects model than a stress-buffering model of social support.

The validity of the Edmonton Symptom Assessment System-Depression item for screening for depression in individuals with cancer pain: A cross-sectional study.

CONTEXT: Depression is common in individuals with cancer and pain, negatively impacts quality of life, treatment adherence, tumor progression, and survival. OBJECTIVES: The primary aims of this study were to (1) evaluate the validity of the Edmonton Symptom Assessment System's depression (ESAS-D) for detecting major depressive disorder (MDD) as diagnosed by a psychiatrist and (2) identify the best cutoff for this purpose in a sample of cancer pain individuals. The secondary aim was to compare ESAS-D with another commonly used screening measure (Patient Health Questionnaire-2 [PHQ-2]) for classifying individuals as meeting or not meeting Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria for depression. METHODS: 49 cancer pain individuals completed the ESAS-D and PHQ-2 Within 2 weeks, a psychiatrist interviewed the participants and determined whether or not they met criteria for MDD based on the DSM-5. RESULTS: The ESAS-D demonstrated acceptable accuracy and validity for classifying MDD. A cutoff of ≥2 was identified as being best able to balance sensitivity (85%) and specificity (76%) and had an overall accuracy of 79%. A receiver operating characteristic curve analysis showed an area under the curve (AUC) of 0.81 (95% confidence interval [CI]: 0.68-0.94). The ESAS-D also compared favorably with the modified Thai PHQ-2 (sensitivity, 75%; specificity, 72%; overall accuracy, 73%; AUC, 0.74 [95% CI: 0.59-0.88]) for identifying MDD individuals. CONCLUSIONS: The ESAS-D showed acceptable sensitivity, specificity, and overall accuracy for screening for MDD in cancer and pain. It could therefore be used to screen for probable depression in this population.

Validation of the PEG Scale in Spanish (PEG-S) Among Adults Receiving Care for Pain in US Primary Care.

This study sought to evaluate the psychometric properties of a Spanish version of the PEG scale (PEG-S, whose items assess Pain intensity and pain interference with Enjoyment of life and General activity) in a sample of Spanish-speaking adults receiving care for pain at primary care clinics in the Northwestern United States. We evaluated the PEG-S's 1) internal consistency, 2) convergent validity, and 3) discriminant validity. All participants (n = 200, mean age = 52 years [SD = 15], 76% women, mean PEG-S score = 5.7 [SD = 2.5]) identified as having Hispanic or Latino ethnicity, and detailed ethnic origin was predominantly Mexican or Chicano (70%). The PEG-S's internal consistency (Cronbach's alpha, .82) was good. Correlations between the PEG-S scale scores and established measures of pain intensity and interference ranged from .68 to .79, supporting the measure's convergent validity. The correlation between the PEG-S scale score and the Patient Health Questionnaire-9 (r = .53) was weaker than those between the PEG-S scale and measures of pain intensity and interference, supporting the measure's discriminant validity. The findings support reliability and validity of the PEG-S for assessing a composite score of pain intensity and interference among Spanish-speaking adults. PERSPECTIVE: We present evidence supporting the reliability and validity of the PEG scale in Spanish (PEG-S) in a sample of adults receiving pain care at primary care clinics in the Northwestern United States. This 3-item composite measure of pain intensity and interference can help clinicians and researchers assess pain among Spanish-speaking adults.

Benefit-risk assessment and reporting in clinical trials of chronic pain treatments: IMMPACT recommendations.

ABSTRACT: Chronic pain clinical trials have historically assessed benefit and risk outcomes separately. However, a growing body of research suggests that a composite metric that accounts for benefit and risk in relation to each other can provide valuable insights into the effects of different treatments. Researchers and regulators have developed a variety of benefit-risk composite metrics, although the extent to which these methods apply to randomized clinical trials (RCTs) of chronic pain has not been evaluated in the published literature. This article was motivated by an Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials consensus meeting and is based on the expert opinion of those who attended. In addition, a review of the benefit-risk assessment tools used in published chronic pain RCTs or highlighted by key professional organizations (ie, Cochrane, European Medicines Agency, Outcome Measures in Rheumatology, and U.S. Food and Drug Administration) was completed. Overall, the review found that benefit-risk metrics are not commonly used in RCTs of chronic pain despite the availability of published methods. A primary recommendation is that composite metrics of benefit-risk should be combined at the level of the individual patient, when possible, in addition to the benefit-risk assessment at the treatment group level. Both levels of analysis (individual and group) can provide valuable insights into the relationship between benefits and risks associated with specific treatments across different patient subpopulations. The systematic assessment of benefit-risk in clinical trials has the potential to enhance the clinical meaningfulness of RCT results.

Quantitative Shear Wave Speed Assessment for Muscles With the Diagnosis of Taut Bands and/or Myofascial Trigger Points Using Probe Oscillation Shear Wave Elastography: A Pilot Study.

OBJECTIVE: To use probe oscillation shear wave elastography (PROSE) with two vibration sources to generate two shear waves in the imaging plane to quantitatively assess the shear wave speeds (SWSs) of muscles with and without the diagnosis of taut bands (TB) and/or myofascial trigger points (MTrPs). METHODS: Thirty-three patients were scanned with the PROSE technique. Shear waves were generated through continuous vibration of the ultrasound probe, while the shear wave motions were detected using the same probe. SWSs for the sides with and without TBs and/or MTrPs were computed and compared. The pressure pain thresholds (PPTs) were measured as an indicator of maximum pain tolerance of patients. The statistical differences between the SWSs with and without TBs and/or MTrPs with different PPT values were analyzed using the nonparametric Wilcoxon rank-sum test. RESULTS: The mean SWSs for the sides with TBs and/or MTrPs are faster than that of the contralateral side without TBs and/or MTrPs. A significant difference was observed between mean SWSs with and without TBs and/or MTrPs without any information of PPT, with rank-sum test P < .005. Additionally, with the information of PPT, a significant difference was observed between mean SWSs for the sides with and without TBs and/or MTrPs, for PPT values between 0 and 50 N/cm2 (P < .005), but for PPT values between 50 and 90 N/cm2 , it was difficult to differentiate mean SWSs with and without TBs and/or MTrPs. CONCLUSION: Our preliminary results show that SWSs measured from patients had a significant difference between the mean SWSs with and without TBs and/or MTrPs.

Clinical outcome assessment in clinical trials of chronic pain treatments.

Clinical outcome assessments (COAs) measure outcomes that are meaningful to patients in clinical trials and are critical for determining whether a treatment is effective. The objectives of this study are to (1) describe the different types of COAs and provide an overview of key considerations for evaluating COAs, (2) review COAs and other outcome measures for chronic pain treatments that are recommended by the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) or other expert groups, and (3) review advances in understanding pain-related COAs that are relevant to clinical trials. The authors reviewed relevant articles, chapters, and guidance documents from the European Medicines Agency and U.S. Food and Drug Administration. Since the original core set of outcome measures were recommended by IMMPACT 14 years ago, several new advancements and publications relevant to the measurement or interpretation of COAs for chronic pain trials have emerged, presenting new research opportunities. Despite progress in the quality of measurement of several outcome domains for clinical trials of chronic pain, there remain some measurement challenges that require further methodological investigation.

Personal resource profiles of individuals with chronic pain: Sociodemographic and pain interference differences.

PURPOSE/OBJECTIVE: Previous studies have demonstrated important associations between personal resources and pain interference. Using latent profile analysis, the present study (a) identified subgroups of individuals with chronic pain who have different personal resource profiles; (b) explored sociodemographic differences among subgroups; and (c) examined how these subgroups differ in pain interference. Research Method/Design: Study 1 is based on daily diary and survey data from 220 individuals with fibromyalgia (FM). Study 2 is based on 4 annual surveys of 483 individuals with long-term neurological/neuromuscular disease or injury, and chronic pain. Modifiable personal resource variables including sense of resilience, social support, pain acceptance, and sleep quality were included in latent profile analyses. RESULTS: Three subgroups were identified in both studies: High, Moderate, and Low Personal Resource groups. In both studies, annual income level was significantly different among subgroups. Study 1 results showed a significant between-groups difference in pain interference across 21-days only between High and Moderate Personal Resource groups controlling for the level of pain intensity and depressive symptoms. In Study 2, however, all subgroups were significantly different with respect to their levels of pain interference at baseline over and above various covariates, with the Low Personal Resource group reporting the highest level of pain interference at baseline. These baseline differences remained stable over 4 years. CONCLUSIONS/IMPLICATIONS: The findings suggest a robust association between economic disparity and personal resource profiles among individuals with chronic pain. The role of different personal resource profiles in pain interference appears to differ by chronic pain condition. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Socioeconomic factors, psychological factors, and function in adults with chronic musculoskeletal pain from rural Nepal.

BACKGROUND: Both socioeconomic and psychological factors have been shown to predict patient function in samples of individuals with chronic pain in Western countries. However, little is known about their role as predictors of function in individuals with chronic pain from developing countries. PURPOSE: The purpose of this study was to examine the associations between measures of socioeconomic factors (income, education) and psychological factors (catastrophizing and resilience) and measures of function in a sample of individuals with chronic pain from rural Nepal. In addition, we sought to evaluate the moderating effects of socioeconomic factors on the associations between the psychological variables and function. METHODS: We interviewed 143 adults with chronic musculoskeletal pain from rural areas of Nepal to assess income, education level, pain intensity, catastrophizing, resilience, physical function, and depression. We performed two regression analyses to evaluate the direct and unique effects of the socioeconomic and psychological variables and pain intensity as predictors of patient function, as well as the moderating influence of income, education level, and pain intensity on the associations between the psychological variables and function. RESULTS: Education and income both predicted physical function, but only income predicted depression. In addition, pain catastrophizing, but not resilience, evidenced a direct and significant independent association with depression. Neither catastrophizing nor resilience made independent and significant direct contributions to the prediction of physical function. The association between resilience and physical function was moderated by pain intensity and income, and income (but not education or pain intensity) moderated the associations between both 1) resilience and depression and 2) catastrophizing and depression. CONCLUSION: The results suggest the possibility that cultural differences may influence the role that psychosocial factors play in chronic pain adjustment. These findings have important implications regarding how psychosocial pain interventions should be adapted by individuals in developing countries.

Effect of Low Back Pain Risk-Stratification Strategy on Patient Outcomes and Care Processes: the MATCH Randomized Trial in Primary Care.

BACKGROUND: The STarT Back strategy for categorizing and treating patients with low back pain (LBP) improved patients' function while reducing costs in England. OBJECTIVE: This trial evaluated the effect of implementing an adaptation of this approach in a US setting. DESIGN: The Matching Appropriate Treatments to Consumer Healthcare needs (MATCH) trial was a pragmatic cluster randomized trial with a pre-intervention baseline period. Six primary care clinics were pair randomized, three to training in the STarT Back strategy and three to serve as controls. PARTICIPANTS: Adults receiving primary care for non-specific LBP were invited to provide data 2 weeks after their primary care visit and follow-up data 2 and 6 months (primary endpoint) later. INTERVENTIONS: The STarT Back risk-stratification strategy matches treatments for LBP to physical and psychosocial obstacles to recovery using patient-reported data (the STarT Back Tool) to categorize patients' risk of persistent disabling pain. Primary care clinicians in the intervention clinics attended six didactic sessions to improve their understanding LBP management and received in-person training in the use of the tool that had been incorporated into the electronic health record (EHR). Physical therapists received 5 days of intensive training. Control clinics received no training. MAIN MEASURES: Primary outcomes were back-related physical function and pain severity. Intervention effects were estimated by comparing mean changes in patient outcomes after 2 and 6 months between intervention and control clinics. Differences in change scores by trial arm and time period were estimated using linear mixed effect models. Secondary outcomes included healthcare utilization. KEY RESULTS: Although clinicians used the tool for about half of their patients, they did not change the treatments they recommended. The intervention had no significant effect on patient outcomes or healthcare use. CONCLUSIONS: A resource-intensive intervention to support stratified care for LBP in a US healthcare setting had no effect on patient outcomes or healthcare use. TRIAL REGISTRATION: National Clinical Trial Number NCT02286141.

Life impact of caregiving for severe childhood epilepsy: Results of expert panels and caregiver focus groups.

Severe epilepsy in children and young adults can significantly affect the lives of their caregivers. However, the lack of a reliable and valid measure of caregiver impact has limited our understanding of the scope and correlates of this impact, as well as our ability to measure the effects of treatments that could lessen it. The purpose of this study was to facilitate focus groups and interviews with an international group of clinician experts and caregivers to identify the most important domains that should be assessed in a measure of caregiver impact. Ten specific subdomains emerged from the panel discussions, which could be classified into the four overarching categories of physical health, mental health, social function, and financial resources. The caregivers highlighted the impact on the subdomains of sleep and fatigue as most critical. A review of existing caregiver impact measures confirmed that there is no measure currently available that assesses all of these relevant domains, indicating the need for the development of such a measure. The current findings highlight the significant life effects of caring for a child with severe epilepsy and can be used to inform the development of such a tool.

The humanistic and economic burden of Dravet syndrome on caregivers and families: Implications for future research.

We reviewed the current literature with respect to the humanistic and financial burdens of Dravet Syndrome (DS) on the caregivers of children with DS, in order to (1) identify key unanswered questions or gaps in knowledge that need to be addressed and then, based on these knowledge gaps, (2) propose a research agenda for the scientific community to address in the coming decade. The findings support the conclusion that caring for a child with DS is associated with significant humanistic burden and direct costs. However, due in part to the paucity of studies, as well as the lack of measures of specific burden domains, there remains much that is not known regarding the burden of caregiving for children with DS. To address the significant knowledge gaps in this area, research is needed that will: (1) identify the specific domains of caregivers' lives that are impacted by caring for a child with DS; (2) identify or, if needed, develop measures of caregiving impact in this area; (3) identify the factors that influence DS caregiving burden; (4) develop and evaluate the efficacy of treatments for reducing the negative impact of DS and its comorbidities on DS caregivers; (5) quantify the direct medical costs associated with DS and DS comorbidities and identify the factors that influence these costs; and (6) quantify and fully explore the indirect costs of DS. Research that addresses these goals will provide the empirical foundation needed for improving the quality of life of children with DS and their families.

Resilience and Function in Adults With Physical Disabilities: An Observational Study.

OBJECTIVES: To determine if resilience is uniquely associated with functional outcomes (satisfaction with social roles, physical functioning, and quality of life) in individuals with physical disabilities, after controlling for measures of psychological health (depression and anxiety) and symptom severity (pain, fatigue, and sleep disturbance); and to examine the potential moderating effect of sex, age, and diagnosis on the hypothesized associations between resilience and function. DESIGN: Cross-sectional survey study. SETTING: Surveys were mailed (81% response rate) to a community sample of 1949 individuals with multiple sclerosis, muscular dystrophy, postpoliomyelitis syndrome, or spinal cord injury. Participants were recruited through the Internet or print advertisement (28%), a registry of previous research participants who indicated interest in future studies (21%), a departmental registry of individuals interested in research (19%), disability-specific registries (18%), word of mouth (10%), or other sources (3%). PARTICIPANTS: Convenience sample of community-dwelling adults aging with physical disabilities (N=1574), with a mean Connor-Davidson Resilience Scale (10 items) score of 29. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Patient-Reported Outcomes Measurement Information System measures of Satisfaction with Social Roles and Activities and Physical Functioning, the World Health Organization's brief Older People's Quality of Life Questionnaire, and the Connor-Davidson Resilience Scale (10 items). RESULTS: After controlling for age, age squared, sex, diagnosis, psychological health, and symptom severity, resilience was significantly and positively associated with satisfaction with social roles (ß=.17, P<.001) and quality of life (ß=.39, P<.001), but not physical function (ß=.04, P>.05). For every 1-point increase in scores of resilience, there was an increase of .50 in the quality of life score and .20 in the satisfaction with social roles score. Sex also moderated the association between resilience and satisfaction with social roles (F1,1453=4.09, P=.043). CONCLUSIONS: The findings extend past research, providing further evidence indicating that resilience plays a unique role in nonphysical functional outcomes among individuals with physical disabilities.

The Pittsburgh Sleep Quality Index: Validity and factor structure in young people.

The Pittsburgh Sleep Quality Index (PSQI) is a widely used measure of sleep quality in adolescents, but information regarding its psychometric strengths and weaknesses in this population is limited. In particular, questions remain regarding whether it measures one or two sleep quality domains. The aims of the present study were to (a) adapt the PSQI for use in adolescents and young adults, and (b) evaluate the psychometric properties of the adapted measure in this population. The PSQI was slightly modified to make it more appropriate for use in youth populations and was translated into Spanish for administration to the sample population available to the study investigators. It was then administered with validity criterion measures to a community-based sample of Spanish adolescents and young adults (AYA) between 14 and 24 years old (N = 216). The results indicated that the questionnaire (AYA-PSQI-S) assesses a single factor. The total score evidenced good convergent and divergent validity and moderate reliability (Cronbach's alpha = .72). The AYA-PSQI-S demonstrates adequate psychometric properties for use in clinical trials involving adolescents and young adults. Additional research to further evaluate the reliability and validity of the measure for use in clinical settings is warranted.

The Number of Ratings Needed for Valid Pain Assessment in Clinical Trials: Replication and Extension.

OBJECTIVES: To provide additional empirical findings regarding the number of pain ratings needed to obtain valid measures for assessing outcomes in pain clinical trials. DESIGN: Secondary analyses of data from a clinical study examining the effects of psychological treatments on pain. Eleven adults with multiple sclerosis and chronic pain reported on four domains of pain intensity (current pain and 24-hour recalled worst, least, and average pain) on four occasions before and after receiving 16 sessions of psychological pain treatments. We evaluated the reliability and validity of four single ratings and 16 different composite scores. RESULTS: Many of the single pain ratings were inadequately reliable while almost all of the composite scores, including the scores created from two ratings, evidenced adequate to excellent reliability. There was a noticeable increase in validity (ability to detect treatment effects) as the number of ratings used increased from one to two. However, there was little change in the validity as the number of items used to create composite scores increased from 2 to 3 or more. The findings also indicated that the scores assessing recalled worst pain were more valid than the scores assessing any of the other pain intensity domains. CONCLUSIONS: Composite pain intensity scores created from two individual ratings of recalled pain appear to be adequately valid for detecting treatment effects. Moreover, the findings indicate that the selection of the pain intensity domain to use as a primary outcome variable may play a more important role than increasing reliability by obtaining more assessments; specifically, ratings of recalled worst pain may be more valid for detecting treatment effects than ratings of average pain.

Resilience predicts functional outcomes in people aging with disability: a longitudinal investigation.

OBJECTIVES: To investigate the links between resilience and depressive symptoms, social functioning, and physical functioning in people aging with disability and to investigate the effects of resilience on change in functional outcomes over time. DESIGN: Longitudinal postal survey. SETTING: Surveys were mailed to a community sample of individuals with 1 of 4 diagnoses: multiple sclerosis, muscular dystrophy, postpoliomyelitis syndrome, or spinal cord injury. The survey response rate was 91% at baseline and 86% at follow-up. PARTICIPANTS: A convenience sample of community-dwelling individuals (N=1594; age range, 20-94y) with multiple sclerosis, muscular dystrophy, postpoliomyelitis syndrome, or spinal cord injury. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Patient Health Questionnaire-9 (to assess depressive symptoms) and Patient Reported Outcomes Measurement Information System (to assess social role satisfaction and physical functioning). RESULTS: At baseline, resilience was negatively correlated with depressive symptoms (r=-.55) and positively correlated with social and physical functioning (r=.49 and r=.17, respectively). Controlling for baseline outcomes, greater baseline resilience predicted a decrease in depressive symptoms (partial r=-.12) and an increase in social functioning (partial r=.12) 3 years later. CONCLUSIONS: The findings are consistent with a view of resilience as a protective factor that supports optimal functioning in people aging with disability.

Mechanisms of hypnosis: toward the development of a biopsychosocial model.

Evidence supports the efficacy of hypnotic treatments, but there remain many unresolved questions regarding how hypnosis produces its beneficial effects. Most theoretical models focus more or less on biological, psychological, and social factors. This scoping review summarizes the empirical findings regarding the associations between specific factors in each of these domains and response to hypnosis. The findings indicate that (a) no single factor appears primary, (b) different factors may contribute more or less to outcomes in different subsets of individuals or for different conditions, and (c) comprehensive models of hypnosis that incorporate factors from all 3 domains may ultimately prove to be more useful than more restrictive models that focus on just 1 or a very few factors.

Development of a bedside pain assessment kit for the classification of patients with osteoarthritis.

There are no standardized bedside assessments for subtyping patients with osteoarthritis (OA) based on pain mechanisms. Thus, we developed a bedside sensory testing kit (BSTK) to classify OA patients based on sensory profiles potentially indicative of pain mechanism. After usability and informal reliability testing (n = 22), the kit was tested in a formal reliability study (n = 20). Patients completed questionnaires and sensory testing: pressure algometry to detect hyperalgesia; repeat algometry after heterotopic noxious conditioning stimulation to measure diffuse noxious inhibitory control (DNIC); light touch using Von Frey filaments; and cold allodynia using a brass rod. The procedure was brief and well tolerated. Algometry and filament testing were highly reliable [intra-class correlation coefficients (ICCs) 0.71-0.91]; DNIC was acceptably reliable (ICCs 0.53-0.91); brass rod reliability was inconclusive. Patients were classified empirically into four groups: "All abnormal findings" (primary and secondary hyperalgesia and dysfunctional DNIC); "all normal findings"; and two intermediate groups. The "all abnormal findings" group had more neuropathic pain symptoms, and lower WOMAC total, stiffness, and activity scores than the "all normal findings" group. Simple BSTK procedures, consolidated in a kit, reliably classified OA patients into subgroups based on sensory profile, suggesting that OA patients differ in underlying pain mechanisms. Further research is needed to confirm these subgroups and determine their validity in predicting response to treatment.

Assessment of pain intensity in clinical trials: individual ratings vs composite scores.

OBJECTIVES: To evaluate the reliability of findings suggesting that composite scores made up of just two ratings of recalled pain may be adequately reliable and valid for assessing outcome in pain clinical trials. DESIGN: Secondary analyses of data from a study where the responsivity of the outcome measures was a critical concern; that is, a study with few subjects testing the effects of a treatment that had only modest effects. Ten adults with spinal cord injury rated four domains of pain intensity (current pain and 24-hour recalled worst, least, and average pain) on four occasions before and after 12 sessions of neurofeedback treatment. We evaluated the reliability and validity of four single ratings and 16 different composite scores. RESULTS: None of the single-item scales performed adequately. However, composite scores made up of two items or more yielded consistent effect size estimates. CONCLUSIONS: The findings provide additional evidence that two-item composite scores may be adequate for assessing the primary outcome of pain intensity in chronic pain clinical trials. Additional research is needed to further establish the generalizability of these findings.

The reciprocal effects of pain intensity and activity limitations: implications for outcomes assessment in clinical trials.

OBJECTIVES: To examine the reciprocal effects of pain intensity and limitations in physical functioning over time. METHODS: This study presents findings from a reanalysis of a 7-center trial conducted in Ontario, Canada, included 209 adults with chronic knee pain secondary to osteoarthritis. Patients were randomized to receive 28 days of therapy with an active solution (1.5% w/w diclofenac sodium in dimethyl sulfoxide) or 1 of 2 control solutions containing no diclofenac. The key outcome measures used in the current analyses were administered throughout the study period and assessed pain intensity, perceived activity limitations, and a composite score measuring both domains. A structural cross-lagged regression approach was used to determine the reciprocal effects of pain and activity limitations over time. RESULTS: In both study groups, participants (N=209) experienced significant reductions in mean pain intensity and activity limitations from baseline to weeks 1, 2, 3, and 4 (P<0.001 for both variables). Similarly, there were significant reductions in the activity limitations outcome at weeks 1 and 4 for the active versus control group (P<0.05 for both). Higher levels of perceived activity limitations predicted more future pain at all time points. Cross-lagged associations in which pain predicted subsequent perceived activity limitations were not significant at any time point. All 3 outcome measures evidenced similar responsiveness to the treatment. CONCLUSION: These analyses showed that a decrease in activity limitations results in a decrease in pain intensity. However, changes in pain intensity had no effect on subsequent activity limitations in the study sample. None of the 3 outcome variables emerged as being more responsive to treatment than the others.