The "funnel hypothesis" of fibromyalgia syndrome (FMS) assumes that the high levels of somatic and psychological symptoms reported by FMS-patients are due to a selection bias of patients seeking for medical specialist care. We tested the hypothesis by comparing FMS-patients from a general population sample and different clinical settings.
From a cross-sectional survey of a representative sample of the German general population, persons meeting FMS-criteria were selected. Consecutive in- and outpatients from German rheumatology, pain medicine, psychosomatic medicine and integrative medicine settings with established or initial diagnosis of FMS were recruited. FMS was diagnosed in all samples by the survey criteria of the regional pain scale. Somatic symptom intensity was measured by 13 items of the Patient Health Questionnaire PHQ 15, depressed mood by the 9-items PHQ 9.
96 persons of the general population, 86 of the rheumatology, 80 of the pain medicine, 69 of the psychosomatic medicine and 58 of the integrative medicine setting were included into the comparison. Patients of the clinical settings reported more pain sites and more somatic and depressive symptoms than FMS-persons of the general population. Patients of the different clinical settings did not differ in the number of pain sites and the intensity of depressive and somatic symptoms.
We found a "funnel" between FMS-persons of the general population and FMS-patients of clinical settings, but not between patients of different levels of care. Patients contacting the health care system did not differ in clinical features.