OBJECTIVES: Pain interference and pain behavior are highly relevant outcomes in patients with rheumatoid arthritis (RA). The Patient-Reported Outcomes Measurement Information System (PROMIS® ) is a universally applicable set of item-banks measuring patient-reported health, and, if applied as computerized adaptive tests (CATs), more efficiently and precisely than current instruments. The objective was to study the psychometric properties of the Dutch-Flemish PROMIS Pain Interference (PROMIS-PI) and the PROMIS Pain Behavior (PROMIS-PB) item-banks in patients with RA.
METHODS: 2029 patients with RA completed the full PROMIS-PI (V1.1, 40-items) and 1554 patients the full PROMIS-PB (V1.1, 39-items). The following psychometric properties were studied: Unidimensionality, local dependence, monotonicity and Graded Response Model (GRM) fit, cross-cultural validity (Differential Item Functioning [DIF] for language [Dutch vs. Flemish]), other forms of measurement invariance, construct validity, reliability, and floor and ceiling effects.
RESULTS: The PROMIS-PI and PROMIS-PB banks were sufficiently unidimensional (Omega-H 0.99,0.95; ECV 0.95,0.78; respectively), had negligible local dependence (0.3%,1.4% of item-pairs), good monotonicity (H 0.75,0.46), and a good GRM model fit (no misfitting items). Furthermore, both item-banks showed good cross-cultural validity (no DIF for language), measurement invariance (no DIF for age, gender, administration mode and disease activity), good construct validity (all hypotheses met), high reliability (>0.90 in the range of patients with RA), and absence of floor and ceiling effects (0% minimum or maximum score, respectively).
CONCLUSIONS: Both PROMIS-PI and PROMIS-PB banks showed good psychometric properties in patients with RA and can be used as CAT in research and clinical practice.