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
T difference for the Functional Assessment of Chronic Illness Therapy (FACIT)-Fatigue total score estimated as 3.1 points, and the responder definition estimated as a 4-point improvement for FACIT-Fatigue total score
Treatment for psoriatic arthritis (PsA), including methotrexate (n = 5, 42%), Defining the responder definition for FACIT-fatigue domains Responder definition (RD), the amount of change an individual patient would have to report to indicate that a relevant treatment benefit has been experienced, was estimated using a repeated measures model (RMM) to assess the relationship between a new anchor, the “Subject Global Impression of Change” (SGIC) score with just three categories (“better”, “the same”, and “worse”), and FACIT-Fatigue domains in PD3 (RMM-RD)
Qualitative FACIT-fatigue study In total, 12 interviews were conducted in February 2017 at two clinical sites (Florida, n = 7; Pennsylvania, n = 5)
Summary
L Test-retest reliability C An acceptable test-retest reliability was observed for I FACIT-Fatigue Experience domain (ICC = 0.80), Impact domain (0.83), and total score (0.83) using pooled data. PD2: OPAL Broaden baseline data pooled with OPAL Beyond Month 6 related concepts were missing and did not suggest any additional items to be assessed, no changes to the FACIT-. The FACIT-Fatigue measurement model was tested FACIT-Fatigue Functional Assessment of Chronic Illness Therapy–Fatigue, PD1/2 using confirmatory factor analysis, which included two Pooled Data 1/2, PsA psoriatic arthritis. Correlation coefficients are all in the expected direction DLQI Dermatology Life Quality Index, FACIT-Fatigue Functional Assessment of Chronic Illness Therapy–Fatigue, ISI Itch Severity Item, PD1/2 Pooled Data 1/2, PtGA Patient’s Global Assessment of Psoriasis and Arthritis (a component of the PtGJS-VAS), PtGJS Patient’s Global Joint and Skin Assessment, PtJA Patient’s Joint.
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