Characteristics of outpatients with functional somatic syndromes at a university hospital's general medicine clinic.

Background: The term medically unexplained symptoms (MUS) is unhelpful for both patients and physicians, and more acceptable illness categories are needed as substitutes for MUS. While some potential substitutes are characterized by excessive psychological burden related to somatic symptoms, "functional somatic syndromes" (FSS) is a category that focuses on physical dysfunction and emphasizes similarities among individual syndromes. Examples of FSS include irritable bowel syndrome, functional dyspepsia, and fibromyalgia syndrome. This study aimed to distinguish FSS from MUS and compare the somatic and psychobehavioral characteristics of FSS with those of other diseases.

Methods: This study included 1975 first-visit outpatients at a Japanese university hospital's general medicine clinic. According to their first-listed diagnosis, they were classified as having FSS, acute infection, organic disease (OD), psychiatric disorder, and unknown condition (UC). The somatic symptom burden and health-related quality of life (HRQoL) were assessed using the Somatic Symptom Scale-8 and EuroQol-5 Dimension, respectively; the involvement of psychobehavioral factors affecting somatic symptoms was also evaluated.

Results: Overall, 33% of patients were included in the FSS category, and 93% of the supposed MUS (FSS and UC) were diagnosed with FSS. Compared with OD, FSS showed more severe somatic symptom burden, similar reduced HRQoL, and higher involvement of psychobehavioral factors.

Conclusion: It can be useful to improve FSS diagnostic skills for the reduction of MUS misdiagnosis. Psychobehavioral factors might be less associated with MUS (in the narrow sense of the term) than FSS.