Assessment of fatigue in primary Sjogren's syndrome:: the Swedish version of the Profile of Fatigue

Objective: To translate the disease-specific Profile of Fatigue (ProF) into Swedish and to evaluate the reliability and validity of the Swedish version. Methods: Forward and back translations were performed. Seventy patients with primary Sjogren's syndrome (PSS), 48 control persons, and two rheumatologists participated. Test - retest reliability, internal consistency, content, construct and discriminant validity were investigated. Results: The translation was accepted without modifications. The test - retest reliability varied between moderate and good ( weighted Kappa = 0.51 - 0.63). Internal consistency was high (Cronbach's alpha = 0.97). Construct validity was proved by significant correlations of the questionnaire items with the Visual Analogue Scale ( VAS) for fatigue (r(s)=0.55 - 0.70), and the Physical Function (PF) (r(s) = -0.20 to -0.41) and Vitality (VT) scales (r(s)= -0.60 to -0.77) of the MOS 36-Item Short-Form Health Survey (SF-36). Content validity was mainly judged as good. A significant difference between the scorings of the patients and the scorings of the control group was seen ( mean difference 1.6, p<0.005). Conclusion: The Swedish version of the ProF is a relatively reliable and valid instrument for the measurement of fatigue in patients with PSS.