Psychometric properties of the Fatigue Severity Scale-Rasch analyses of individual responses in a XXXX cohort.

@entity1 @entity64 @entity1295
BACKGROUND: The psychometric properties of the Fatigue Severity Scale (FSS) have not been tested in @entity1 with @entity64 , despite its being the most frequently used instrument measuring @entity1295 in this population. OBJECTIVE: The objective of our study was to assess the psychometric properties of the FSS using both traditional and modern test theory approaches in @entity1 with @entity64 . DESIGN AND SETTING: A total of 119 @entity1 admitted to two hospitals in Norway with their first @entity64 were recruited to a longitudinal study of poststroke @entity1295 . Data on socio-demographics, @entity1295 and other clinical variables were collected by face-to-face interviews using standardized questionnaires or by mailed questionnaires at four time points six months apart. A total of 428 responses on the FSS were analysed. The internal scale validity, @entity1 response validity, unidimensionality, and uniform differential item functioning were assessed by applications of a Rasch model and by Cronbach's alpha. Additionally, concurrent validity was assessed using bivariate correlation analysis. RESULTS: Items #1 and #2 in the original FSS demonstrated unacceptable high mean-square values. When these two items were removed, the psychometric properties in FSS-7 demonstrated better evidence of validity. No systematic differential item functioning of the items in FSS-7 was found in relation to any of the analysed variables. CONCLUSION: In @entity1 with @entity64 , the FSS-7 showed better psychometric properties and had better potential to detect changes in @entity1295 over time than the FSS-9 version, suggesting satisfactory grounds for removal of items #1 and #2 for its application.
