Psychometric Properties and Domains Covered by Patient-Reported Outcome Measures Used in Trials Assessing Interventions for Chronic Pain

Objective To identify the patient reported outcome measures (PROMs) used in clinical trials assessing interventions for chronic pain, describe their psychometric properties and the clinical domains they cover. Study design and setting We identified phase 3 or 4 interventional trials on adult participants (age >18) registered in clinicaltrials.gov between January 1, 2021 to December 31, 2022 and which provided “chronic pain” as a keyword condition. We excluded diagnostic studies and phase 1 or 2 trials. In each trial, one reviewer extracted all outcomes registered and identified those captured using PROMs. For each PROM used in more than 1% of identified trials, two reviewers assessed whether it covered the six important clinical domains from the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT): pain, emotional functioning, physical functioning, Participant ratings of global improvement of global improvement, symptoms and adverse events, and participant disposition (e.g., adherence to medication). Second, reviewers searched PubMed for both the initial publication and latest review reporting the psychometric properties of each PROM and their content validity, structural validity, internal consistency, reliability, measurement error, hypotheses testing, criterion validity and responsiveness using published criteria from the literature. Results In total, 596 trials assessing 4843 outcomes were included in the study (median sample size 60, interquartile range 40 to 100). Trials evaluated behavioral (22%), device-based (21%) and drug-based (10%) interventions. Of 495 unique PROMs, 55 were used in more than 1% trials (16 were generic pain measures; 8 were pain measures for specific diseases; 30 were measures of other symptoms or consequences of pain). About 50% PROMs had more than 50% of psychometric properties rated as sufficient. Scales often focused on a single clinical domain. Only 25% trials measured at least three clinical domains from IMMPACT. Conclusion Only half of PROMs used in trials for chronic pain had sufficient psychometric properties for more than 50% of criteria assessed. Few PROMs assess more than one important clinical domain. Only 25% of trials measure more than 3/6 clinical domains considered important by IMMPACT.