Reliability and validity of the Swedish Fatigue Assessment Scale when self-administrered by persons with mild to moderate stroke

Abstract

Objective: To examine internal consistency, test-retest reliability, floor/ceiling effects and construct validity of the Fatigue Assessment Scale (FAS), when self-administrated by persons with mild to moderate stroke.

Method: The FAS was translated into Swedish and tested for psychometric properties when self-administrated by persons with mild to moderate stroke. Participants, consequently selected from the stroke unit admission register received a letter with three questionnaires: the FAS, Short Form Health Survey (SF-36) subscale for vitality and Geriatric Depression Scale, GDS-15. Within two weeks, a second letter with FAS was sent for re-test.

Result: Seventy-tree persons with mild to moderate stroke participated in the study. Internal consistency was good (Cronbach’s alpha 0.82). The test and retest reliability of individual items showed that five items out of 10 items were good (weighted kappa > 0.60), four were moderate (0.40-0.60), and one was fair (0.22). The relative reliability between total scores was good (ICC _3.1 = 0.73) and the absolute reliability was nine points, meaning that a change of at least nine points in total score implies a real change of fatigue level. Correlation analysis showed that the Swedish FAS correlated with the SF-36 subscale for vitality (r_s = - 0.73) and GDS-15 (r_s = 0.62), suggesting convergent construct validity. There were no floor or ceiling effects.

Conclusion: The Swedish translation of the FAS used as a self-administrated questionnaire is reliable and valid for measuring fatigue in persons with mild to moderate stroke.

Keywords:

• Stroke
• Fatigue
• Questionnaire
• Reliability
• Floor/ceiling effects
• Construct validity