Combining online and in-person methods to evaluate the content validity of PROMIS fatigue short forms in rheumatoid arthritis.

PURPOSE: Fatigue is frequent and often severe and disabling in RA, and there is no consensus on how to measure it. We used online surveys and in-person interviews to evaluate PROMIS Fatigue 7a and 8a short forms (SFs) in people with RA. METHODS: We recruited people with RA from an online patient community (n = 200) and three academic medical centers (n = 84) in the US. Participants completed both SFs then rated the comprehensiveness and comprehensibility of the items to their fatigue experience. Cognitive debriefing of items was conducted in a subset of 32 clinic patients. Descriptive statistics were calculated, and associations were evaluated using Pearson and Spearman correlation coefficients. RESULTS: Mean SF scores were similar (p ≥ .61) among clinic patients reflecting mild fatigue (i.e., 54.5-55.9), but were significantly higher (p < .001) in online participants. SF Fatigue scores correlated highly (r ≥ 0.82; p < .000) and moderately with patient assessments of disease activity (r ≥ 0.62; p = .000). Most (70-92%) reported that the items "completely" or "mostly" reflected their experience. Almost all (≥ 94%) could distinguish general fatigue from RA fatigue. Most (≥ 85%) rated individual items questions as "somewhat" or "very relevant" to their fatigue experience, averaged their fatigue over the past 7 days (58%), and rated fatigue impact versus severity (72 vs. 19%). 99% rated fatigue as an important symptom they considered when deciding how well their current treatment was controlling their RA. CONCLUSIONS: Results suggest that items in the single-score PROMIS Fatigue SFs demonstrate content validity and can adequately capture the wide range of fatigue experiences of people with RA.