Objective: The Functional Assessment of Chronic Illness Therapy–Fatigue (FACIT-F) is validated for measuring fatigue in rheumatoid arthritis (RA). However, 10 of 13 FACIT-F items are identified as relevant to patients with RA. The Patient-Reported Outcomes Measurement Information System (PROMIS) uses an item response theory–calibrated T score metric. The PROMIS Fatigue item bank includes the FACIT-F items, enabling score conversion. The performance of converted PROMIS Fatigue scores has not been evaluated in RA populations or clinical trials. Our objective was to assess the performance of converted PROMIS Fatigue scores in 2 RA clinical trials of baricitinib. Methods: Crosswalk tables and pattern-scoring methods converted FACIT-F scores to PROMIS Fatigue for both the 13-item FACIT-F and the 10-item RA-optimized FACIT-F instrument, in 2 RA clinical trials evaluating baricitinib, RA-BEAM, and RA-BEACON. RA-BEAM patients had an inadequate response to methotrexate. RA-BEACON patients had an inadequate response or intolerance to ≥1 tumor necrosis factor inhibitor. Baricitinib was compared to all treatment arms via analysis of covariance on PROMIS Fatigue score conversions. Results: Baseline FACIT-F–derived PROMIS Fatigue scores reflected severe fatigue across treatment groups and were similar using different scoring methods. At week 24 in both studies, baricitinib was associated with clinically meaningful improvements in PROMIS Fatigue scores. PROMIS Fatigue scores were consistent for conversion methods and for the 13-item or 10-item FACIT-F. Conclusion: All 4 conversion methods showed differentiation of active treatment compared with placebo from week 12, supporting the use of the PROMIS Fatigue and converting the 10-item FACIT-F to assess fatigue and demonstrate treatment benefit in RA clinical trials on a standardized metric.
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