To translate the Fibromyalgia Impact Questionnaire (FIQ) into German and to evaluate its reliability and validity for the use of German speaking patients with fibromyalgia (FM).
We administered the FIQ to 55 patients with FM (15 patients filled out the questionnaire 10 days later) together with German versions of the Stanford Health Assessment Questionnaire (HAQ), the Medical Outcomes Survey Short Form-36 (SF-36), and a tender point count (TPC). All patients were asked about the severity of pain today (10 cm visual analog scale) and the duration of symptoms. Tenderness thresholds were assessed by dolorimetry at all tender points with a Fisher dolorimeter and laboratory tests were obtained. Test-retest reliability was assessed using Spearman correlations. Internal consistency was evaluated with Cronbach's alpha of reliability. Construct validity of the FIQ was evaluated by correlating the HAQ and subscales of the SF-36 as well as the TPC and the tenderness thresholds.
Mean age of participants was 54.3 years and mean duration of symptoms 9.5 years. Test-retest reliability was between 0.62 and 1 for the physical functioning as well as for the total FIQ and other components. Internal consistency was 0.92 for the overall FIQ. Significant correlations were obtained between the FIQ items, the HAQ, and the SF-36.
The German FIQ is a reliable and valid instrument for measuring functional disability and health status in German patients with FM.