Objective: Graduated treatment of patients with functional somatic syndromes (FSS) and fibromyalgia syndrome (FMS) depending on their severity has been recommended by recent guidelines. The Patient Health Questionnaire 15 (PHQ 15) is a validated measure of somatic symptom severity in FSS. We tested the discriminant and transcultural validity of the PHQ 15 as a generic measure of severity in persons with FMS.
Methods: Persons meeting recognized FMS-criteria of the general German population (N=98), of the US National Data Bank of Rheumatic Diseases (N=440), and of a single German pain medicine center (N=167) completed validated self-report questionnaires on somatic and psychological distress (Polysymptomatic Distress Scale, Patient Health Questionnaire 4), health-related quality of life (HRQOL) (Short Form Health Survey 12 or 36) and disability (Pain Disability Index). In addition, self-reports of working status were assessed in the clinical setting. Overall severity of FMS was defined by PHQ 15 scores: mild (0-9), moderate (10-14) and severe (15-30).
Results: Persons with mild, moderate and severe FMS did not differ in age and gender. Irrespective of the setting, persons with severe FMS reported more pain sites, fatigue, depressed mood, impaired HRQOL and disability than persons with moderate or mild FMS. Patients with severe FMS in the NDB and in the German clinical center reported more work-related disability than patients with mild FMS.
Conclusion: The PHQ 15 is a valid generic measure of overall severity in FMS.
Keywords: Disability; Fibromyalgia syndrome; Functional somatic syndrome; Patient Health Questionnaire 15; Psychological distress; Severity grading; Validity.
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