Test-retest reliability, internal consistency and concurrent validity of Fatigue Severity Scale in measuring post-stroke fatigue.

BACKGROUND Post-stroke fatigue (PSF) is a common complaint among stroke survivors and has significant impacts on recovery and quality of life. Limited tools that measure fatigue have been validated in stroke. AIM The purpose of this study was to determine the psychometric properties of Fatigue Severity Scale (FSS) in patients with stroke. DESIGN Cross-sectional study. SETTING Teaching hospital outpatient setting. POPULATION Fifty healthy controls (mean age 61.1±7.4 years; 22 males) and 50 patients with stroke (mean age 63.6±10.3 years; 34 males). METHODS FSS was administered twice approximately a week apart through face-to-face interview. In addition, we measured fatigue with Visual Analogue Scale - Fatigue (VAS-F) and Short-Form Health Survey 36 version 2 vitality scale. We used Cronbach alpha to determine internal consistency of FSS. Reliability and validity of FSS were determined by intraclass correlation coefficient (ICC) and Spearman correlation coefficient (r). RESULTS FSS showed excellent internal consistency for both stroke and healthy groups (Cronbach's alpha >0.90). FSS had excellent test-retest reliability for stroke patients and healthy controls (ICC=0.93 and ICC=0.90, respectively). The scale demonstrated good concurrent validity with VAS-Fatigue (all r>.60) and a moderate validity with the SF36-vitality scale. Furthermore, FSS was sensitive to distinguish fatigue in stroke from the healthy controls (P<0.01). CONCLUSIONS FSS has excellent internal consistency, test-retest reliability and good concurrent validity with VAS-F for both groups. CLINICAL REHABILITATION IMPACT This study provides evidence that FSS is a reliable and valid tool to measure post-stroke fatigue and is readily to be used in clinical settings.