Evaluating Patient-Reported Outcome Measurement in Fibromyalgia Clinical Trials: A Meta-Analysis of Alignment with IMMPACT Recommendations

Purpose Fibromyalgia diagnosis and treatment response depend mostly on patient report, making patient-reported outcomes central to trial evidence. The Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials provides recommendations for standardized outcome domains and endorsed patient-reported instruments in chronic pain trials. Whether fibromyalgia trials have converged on a common set of instruments remains unclear. We evaluated instrument standardization and IMMPACT alignment among registered fibromyalgia trials. Methods We conducted a cross-sectional meta-research analysis of 916 interventional fibromyalgia trials registered on ClinicalTrials.gov. Outcomes were classified against an inductively built dictionary of patient-reported outcome instruments, with alignment defined as registration of at least one consensus-body-endorsed instrument. Completeness and alignment were assessed relative to the consensus body's 2005 publication, and cohort assembly and instrument detection were independently verified. Results Of 916 eligible trials, 778 (84.9%) named a patient-reported outcome instrument, rising from 47.4% in 2005 to a peak near 98% in 2021. One hundred and two distinct instruments were registered, but only 49.1% of these trials included one the consensus body endorses. The most common measure was the Fibromyalgia Impact Questionnaire, an unendorsed fibromyalgia-specific tool, and the non-endorsed Visual Analog Scale was registered nearly twice as often as the consensus-body-endorsed Numeric Rating Scale (348 vs. 192 trials). Conclusion Fibromyalgia trials have largely resolved whether to measure patient-reported outcomes, but instrument selection remains fragmented despite two decades of guidance, limiting comparability across trials. Requiring a consensus-body-endorsed instrument alongside a disease-specific measure would close this gap without sacrificing disease-specific detail.