Quality of life in patients with fibromyalgia: validation and psychometric properties of the German Quality of Life Scale (QOLS-G)

Our objectives were to translate the Quality of Life Scale (QOLS) into German and to evaluate its reliability and validity for the use in patients with fibromyalgia (FMS). Together with German versions of the Fibromyalgia Impact Questionnaire (FIQ), the SF-36, a tender point count (TPC) and other questionnaires, we administered the QOLS to 146 patients with FMS. Patients were asked about the severity of pain today (VAS) and the duration of symptoms. Test-retest reliability was assessed using Spearman's correlations. Internal consistency was evaluated with Cronbach's alpha. Construct validity of the QOLS was evaluated by correlating the QOLS with the FIQ, the SF-36, the Beck Depression Inventory (BDI), and the Symptom Checklist (SCL-90-R) as well as with the pain variables. An exploratory factor analysis (EFA) was also conducted. Mean age was 53.1 years. Means were for pain today 6.8 and for duration of symptoms 11.8 years. Test-retest reliability for the total QOLS was rho = .91. Internal consistency was alpha = .90. Low-to-moderate correlations were obtained between the QOLS and the total FIQ (rho = -.42**), the SF-36 (e.g. physical functioning rho = .37**; mental health rho = .56**) as well as the pain variables (VAS rho = -.11 ns; TPC rho = -.20*). Psychological variables were moderately to substantially correlated with the QOLS (e.g. BDI rho = -.61**). An EFA suggested a three-factor solution. The QOLS-G is a reliable and valid instrument for measuring quality of life in German patients with FMS.