Background/Purpose: Patient-Reported Outcomes Measurement Information System (PROMIS) provides clinicians and researchers access to reliable, valid measures of health status to resolve many challenges associated with the comparability and interpretability in OA. However, for adults with OA, longitudinal construct validity, i.e. ability of a measurement instrument to detect changes over time, of PROMIS instruments is unknown. Our purpose is to evaluate the longitudinal construct validity for 4 PROMIS Short Forms: Physical Function, Pain Interference, Depression, and Anxiety among those with knee OA following the recommended guidelines of the Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN).  

Methods: We performed a longitudinal analysis using the pooled, similar treatment effects that resulted from a randomized trial comparing Tai Chi with physical therapy in adults with symptomatic knee OA (ACR criteria). Participants completed questionnaires at baseline and after 12-week intervention. Longitudinal construct validity was investigated according to the COSMIN standard by testing 6 a priori hypotheses regarding expected Spearman’s correlations between changes in PROMIS scores and changes in legacy measures (Short Form-36 subscales, WOMAC, Beck Depression, Perceived Stress, 6-minute and 20-Meter Walk Tests). After an item-by-item comparison of PROMIS short forms and legacy measures, an expert group formulated each hypothesis by including direction, strength, and rationale for expected correlation. Each PROMIS short form was assigned an overall rating of longitudinal construct validity based on its total number of confirmed hypotheses: High, 5-6 of 6 (≥75%); Moderate, 3-4 of 6 (50%≤ x <75%); or Poor, 0-2 of 6 (<50%).

Results: We examined 165 participants (mean age 61 years, 70% female, 53% white, 92% Kellgren/Lawrence Grade ≥ 2). We confirmed 5 of 6 a priori hypotheses (83%) for PROMIS Physical Function. For Pain Interference, Depression, and Anxiety, respectively 4 of 6 (67%), 3 of 6 (50%) and 4 of 6 (67%) hypotheses were confirmed. Therefore, PROMIS Physical Function has high longitudinal construct validity, and PROMIS Depression, Anxiety, and Pain Interference have moderate longitudinal construct validity.

Conclusion: Our results support that these 4 PROMIS short forms: Physical Function, Pain Interference, Depression, and Anxiety have the ability to detect changes over time for their intended construct among people with symptomatic knee OA. In addition, we provide an important standard of reference for clinicians and researchers to better apply or interpret these instruments in future clinical trials. Additional studies using PROMIS instruments of different domains or among cross-cultural OA populations are warranted.