Abstract
Fibromyalgia (FM) and Chronic Fatigue Syndrome (CFS) are related yet overlapping disorders; the current case definitions prohibit a clear-cut differential diagnosis. These diagnostic criteria mainly address the impairment level of the World Health Organization's International Classification of Functioning, Disability and Health. This study aimed at comparing activity limitations and participation restrictions in patients with FM (n = 90) and CFS (n = 47). The Chronic Fatigue Syndrome Activities and Participation Questionnaire (CFS-APQ) was used for assessing functionality in both groups. The convergent validity of the scores obtained with the questionnaire with visual analogue scales for pain, fatigue and concentration was investigated in FM patients, as well as the content validity. No differences in total scores and 25 out of 26 individual items on the CFS-APQ were observed between the 2 groups (independent samples Mann-Whitney U test). This sample of FM patients reported to be more disabled in ‘sitting for two hours’ as compared to the CFS group (mean scores 3.0 ± 1.0 and 2.3 ± 1.0; P = .004). Four hundred and thirty-seven of the 497 (87.9%) responses to the request to list difficult activities matched the content of the CFS-APQ. The overall scores of the CFS-APQ correlated statistically significant in respect to visual analogue scales for pain and concentration (Spearman rho for the total scores ranged between .44 and .49). These data question the disease specificity of the CFS-APQ for CFS, but suggests its applicability in ‘the Chronic Pain-Fatigue Syndromes.’ The present report provides evidence for both the content and convergent validity of the CFS-APQ in FM patients.