Patients and methods: Between February 2011 and September 2011, a total of 120 female patients (mean age 45±9.1 years; range, 20 to 60 years) admitted to our outpatient clinic with extensive pain and fatigue and diagnosed with FM according to 1990 and 2010 American College of Rheumatology criteria were included in this study. The MFI-20 was translated according to forward-backward translation procedure. For the test-retest reliability, the patients re-filled out the scale 48 hours after the first application. Structural validity was evaluated with confirmatory factor analysis (CFA). Reliability was assessed by internal consistency with Cronbach alpha and test-retest reliability was assessed by intra-class correlation coefficient (ICC). For convergent validity, Spearman rho correlation coefficient was used for relevance analysis with the Fatigue Impact Scale (FIS), visual analog scale (VAS)-pain, VAS-fatigue, and Short Form-36 (SF-36) questionnaires.

Results: The total Cronbach alpha coefficient was found to be 0.92 (range, 0.78 to 0.93). The CFA showed good structural validity and revealed five dimensions. The ICC coefficient was found to be 0.934. All correlation coefficients between the MFI and FIS were calculated as above 0.80, indicating a strong relationship.

Conclusion: The results of this study show that the Turkish version of the MFI-20 has a high internal consistency and reasonable construct validity. It is a valid and reliable measurement of the assessment of fatigue in patients with FM multidimensionality. Keywords : Fibromyalgia, multidimensional fatigue inventory, reliability, validity