Prevalence of medically unexplained symptoms in adults who are high users of healthcare services and magnitude of associated costs: a systematic review

Introduction Medically unexplained symptoms (MUS) is a common clinical syndrome in primary and secondary healthcare service. Outcomes for patients with persistent MUS include increased disability, poorer quality of life and higher healthcare costs. The aim of this systematic review was to determine the prevalence of MUS in patients who are high users of healthcare or high-cost patients in comparison with routine users and the magnitude of associated costs. Design A systematic review of the available literature. Data sources and eligibility criteria The following electronic databases were systematically searched without language restriction from inception to June 2018 and updated on 22 October 2021: MEDLINE, PsycINFO, EMBASE, CINAHL and PROSPERO. Inclusion criteria included studies investigating adults aged ≥18 years, who were high healthcare users or accrued high healthcare costs, in which the prevalence and/or associated costs of MUS was quantified. Two reviewers independently extracted information on study characteristics, exposure and outcomes. Results From 5622 identified publications, 25 studies from 9 countries involving 31 650 patients were selected for inclusion. Due to high risk of bias in many studies and heterogeneity between studies, results are described narratively. There were wide variations in prevalence estimates for MUS in high users of healthcare (2.9%-76%), but MUS was more prevalent in high use groups compared with low use groups in all but one of the 12 studies that included a comparator group. Only three studies investigated healthcare costs associated with MUS, and all three reported greater healthcare costs associated with MUS. Conclusion MUS has been found to be more prevalent in high use healthcare populations than comparator groups, but the magnitude of difference is difficult to estimate due to considerable heterogeneity between studies and potential for bias. Future studies should prioritise a standardised approach to this research area, with agreed definitions of MUS and high healthcare use. PROSPERO registration number CRD42018100388.