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.