LAUSR

OBJECTIVE Epidemiological research in functional somatic disorders such as irritable bowel syndrome, fibromyalgia, chronic fatigue syndrome, and bodily distress syndrome and related conditions such as health (illness) anxiety is often based on self-reported questionnaires or layman interviews. This study presents and describes the Research Interview for Functional somatic Disorders (RIFD) and provides first data regarding RIFD's ability to identify cases with functional somatic disorders and health anxiety in a two-phase design following self-reported symptom questionnaires. METHODS RIFD was performed by phone by trained family physicians on a stratified subsample of 1590 adults from a Danish general population cohort (n = 7493). Criterion validity was tested in a small preliminary test including 25 RIFD participants using Schedules of Clinical Assessment in Neuropsychiatry (SCAN), performed by a specialist in functional somatic disorders, as gold standard. Interrater reliability between interviewers was tested in 15 participants. RESULTS Compared with the comprehensive SCAN, preparation and conduction of RIFD were feasible and prompt. RIFD was well accepted by both interviewers and interviewees. RIFD identified cases with significantly more impairment than identified non-cases. Based on small preliminary tests, RIFD showed promising psychometric properties. CONCLUSION RIFD was a feasible, well-accepted and promising instrument for use in large epidemiological studies. However, larger studies investigating its psychometric properties are needed.