Abstract
BackgroundFatigue is a key symptom in patients with systemic lupus erythematosus (SLE), and regulatory bodies recommend its assessment in clinical trials of SLE therapies.MethodsThis post hoc pooled analysis of the three BeLimumab In Subjects with Systemic lupus erythematosus (BLISS) Phase 3 randomised, double-blind, parallel-group controlled trials evaluated the measurement properties of the Functional Assessment of Chronic Illness Therapy (FACIT)-Fatigue. Patients (N = 2520) completed the FACIT-Fatigue every 4 weeks from baseline until the end of each study period. Internal consistency, test–retest reliability, convergent validity, and ability to detect changes in SLE were evaluated for the FACIT-Fatigue.ResultsThe FACIT-Fatigue showed good internal consistency reliability (Cronbach’s alpha > 0.90), very good test–retest reliability (0.76 ≤ intraclass correlation coefficient ≤ 0.92), and moderate-strong convergent validity (0.49 ≤ |r| ≤ 0.86) against scale and summary measure scores from the Short Form 36 Health Survey Version 2. Correlations between FACIT-Fatigue and British Isles Lupus Assessment Group (BILAG) General/Musculoskeletal scores (0.24 ≤ |r| ≤ 0.43) supported convergent validity. Correlations between FACIT-Fatigue and the Safety of Estrogens in Lupus Erythematosus National Assessment-Systemic Lupus Erythematosus Disease Activity Index (SELENA-SLEDAI) scores and SLE annualised flare rate were weak but in the expected direction (ranging from − 0.02 to − 0.25). Known-groups validity testing showed that the FACIT-Fatigue can significantly discriminate between patient groups with differing scores for SELENA-SLEDAI, BILAG (General and Musculoskeletal) ratings, and Physician’s Global Assessment (PGA). Patients showing improvement in PGA and meeting the BILAG responder criteria had significantly higher mean improvement in FACIT-Fatigue scores than those without improvements in either measure (Week 52 mean score difference [95% confidence interval]: − 4.0 [− 5.0, − 3.0] and −2.2 [−3.1, −1.2], respectively; both p < 0.0001). The range of important (i.e. meaningful) change in FACIT-Fatigue, based on multiple anchors, was 3–6 points.ConclusionsThe FACIT-Fatigue demonstrated adequate psychometric properties in patients with SLE. The body of evidence from the three BLISS trials (both pooled and individually) supports the FACIT-Fatigue as a reliable and valid measure of SLE-related fatigue in clinical trials.Clinical trial identifiersBLISS-SC (NCT01484496), BLISS-52 (NCT00424476), and BLISS-76 (NCT00410384).
Highlights
Fatigue is a key symptom in patients with systemic lupus erythematosus (SLE), and regulatory bodies recommend its assessment in clinical trials of SLE therapies
Both the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) recognise that fatigue is an important symptom of SLE, and recommend that this should be assessed in clinical trials of SLE therapies [8, 9], using a reliable patient-reported outcome (PRO) measure [8]
To strengthen the currently available evidence in this area, the present study investigated the psychometric properties of the Functional Assessment of Chronic Illness Therapy (FACIT)-Fatigue in SLE using data from three randomised controlled trials (RCTs) of belimumab [14,15,16], a human immunoglobulin G1-λ monoclonal antibody approved for the treatment of SLE in adults (Europe and USA) and children (USA only) who are receiving standard therapy [17,18,19]
Summary
Fatigue is a key symptom in patients with systemic lupus erythematosus (SLE), and regulatory bodies recommend its assessment in clinical trials of SLE therapies. Given the substantial burden of fatigue on patients with SLE, regular assessment is important to ensure it is managed optimally, with strategies tailored to the individual patient [7] Both the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) recognise that fatigue is an important symptom of SLE, and recommend that this should be assessed in clinical trials of SLE therapies [8, 9], using a reliable patient-reported outcome (PRO) measure [8]. In an analysis of data from a 52-weekplacebo-controlled trial in patients with moderately to severely active SLE [12], the FACIT-Fatigue showed good internal consistency reliability (Cronbach’s alpha > 0.95 at all visits) and detected improvement in clinical outcome measures of SLE disease activity (British Isles Lupus Activity Group [BILAG] General and BILAG Musculoskeletal) and worsening in patients’ global assessment [11]. Results showed significant and longitudinally consistent correlations between the FACIT-Fatigue and other measures including pain intensity and interference, the Short Form 36 Health Survey Version 2 (SF-36v2)
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