Can the Fatigue Severity Scale 7-item version be used across different patient populations as a generic fatigue measure - a comparative study using a Rasch model approach

Table 5 Differential item functioning of fatigue severity scale-7 by diagnostic groups

Item	Differential item functioning
3	MS – HIV/AIDS Stroke – HIV/AIDS
4	None
5	MS – Stroke**
6	MS – HIV/AIDS*
7	None
8	None
9	MS – HIV/AIDS** Stroke – HIV/AIDS*

*Indicates significant differences (*p < 0.05; **p < 0.01) using Mantel-Haenszel statistic for polytomous scales. The statistic indicated significant differential item function by diagnostic group for items #3 (a relatively more difficult item for the HIV/AIDS group compared to the MS and stroke groups, #5 (a relatively easier item for the MS group compared to the stroke group, #6 (a relatively easier item for the MS group compared to the HIV/AIDS group, and #9 (a relatively easier item for the HIV/AIDS group compared to the MS or stroke groups). Item calibrations for items #4, #7, and #8 did not differ by diagnostic group.

ISSN: 1477-7525