Abstract
BackgroundTo evaluate the measurement properties (e.g., content validity, reliability, and ability to detect change) of the Functional Assessment of Chronic Illness Therapy (FACIT)-Fatigue scale in patients with active psoriatic arthritis (PsA).MethodsOne-on-one semi-structured qualitative interviews with adult patients with active PsA evaluated the content validity of FACIT-Fatigue. Quantitative measurement properties were evaluated using data from phase III tofacitinib randomized controlled trials (RCTs) in PsA: OPAL Broaden (NCT01877668) and OPAL Beyond (NCT01882439).ResultsOf 12 patients included in the qualitative study, 2 (17%) had mild, 8 (67%) had moderate, and 2 (17%) had severe PsA disease activity; 7 (58%) attributed fatigue to PsA, and 7 (58%) rated fatigue as important or extremely important. Most patients considered the FACIT-Fatigue items relevant to their PsA experience, and understood item content and response options as intended. In the psychometric analysis of RCT data, a second-order confirmatory factor model fit the data well (Bentler’s Comparative Fit Index ≥0.92). FACIT-Fatigue demonstrated good internal consistency (Cronbach’s coefficient α ≥ 0.90), test-retest reliability (Intraclass Correlation Coefficient ≥ 0.80) and a strong correlation with SF-36 Vitality (r > 0.80). A robust relationship between disease activity (based on Patient’s Global Assessment of Psoriasis and Arthritis) and FACIT-Fatigue was observed (effect sizes > 1.4), with clinically important difference for the FACIT-Fatigue total score estimated as 3.1 points, and the responder definition estimated as a 4-point improvement for FACIT-Fatigue total score.ConclusionFatigue was confirmed to be an important symptom to patients with PsA, and FACIT-Fatigue was found to be a reliable and valid measure in this population.
Highlights
To evaluate the measurement properties of the Functional Assessment of Chronic Illness Therapy (FACIT)-Fatigue scale in patients with active psoriatic arthritis (PsA)
Qualitative FACIT-Fatigue study In total, 12 interviews were conducted in February 2017 at two clinical sites (Florida, n = 7; Pennsylvania, n = 5)
This study evaluated the content validity and quantitative measurement properties to assess whether FACIT-Fatigue is fit for purpose as a measure to evaluate this important domain in Randomized controlled trial (RCT) in patients with PsA
Summary
To evaluate the measurement properties (e.g., content validity, reliability, and ability to detect change) of the Functional Assessment of Chronic Illness Therapy (FACIT)-Fatigue scale in patients with active psoriatic arthritis (PsA). Psoriatic arthritis (PsA) is a chronic inflammatory disease occurring in 6–42% of patients with psoriasis [1]. It is characterized by joint inflammation, enthesitis, dactylitis, and spondylitis, and is often associated with generalized fatigue [1,2,3]. Recognized as a core domain for assessment in RCTs, there is currently no universally accepted measure of fatigue recommended to evaluate this construct in patients with PsA. When measuring a construct within the RCT setting, it is important to ensure the relevance and comprehension of a questionnaire to the target population, and its reliability, validity, and ability to detect change [9,10,11]
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