OBJECTIVES : This post-hoc analysis aimed to determine thresholds for within-patient meaningful improvement (WPMI) for two patient-reported outcome (PRO) instruments among patients with rheumatoid arthritis (RA), RASIQ and FACIT-fatigue. RASIQ comprises three domains (Joint Pain [JP], Joint Stiffness [JS] and Impact [IM]) scored from 0–100; the 13-item questionnaire FACIT-Fatigue assesses self-reported fatigue and its impact upon daily activities and function over the past seven days (range 0–52).

METHODS : Data from two Phase 2 trials in RA were used in the analyses. Primary analyses were based on anchor-based methods, with multiple anchors used. Analyses of measurement error and reliable change provided supportive data. For each scale, mean change from baseline was calculated across anchor-based categories of change; WPMI was estimated as the mean change to Week 24 for a pre-defined meaningful improvement in each category. Receiver operating characteristics (ROC) curve analyses were used to evaluate the sensitivity and specificity of identified thresholds.

RESULTS : For RASIQ, anchor-based WPMI was determined as a change between –30 and –24 points for the JP scale, –25 to –18 for the JS scale, and –21 to –15 for the IM scale. For all three scales, these ranges were well beyond measurement error. ROC curve analyses indicated that values of sensitivity and specificity were reasonable at the WPMI estimated by the anchor-based methods. For FACIT-fatigue, WPMI estimates ranged from 9.7 to 11.3 points; estimates of reliable change were smaller (range 3.2–4.9). The cut-point associated with the best sensitivity / specificity balance based on ROC curve analyses was slightly smaller than WPMI estimated by anchor-based mean change methods.

CONCLUSIONS : Derivation of WPMI for RASIQ and FACIT-Fatigue will enable broader use of these PROs to better evaluate and interpret treatment benefit in future RA studies.

Funding: GSK [212734]