Syndromal definitions and epidemiology of MUS
Insights and recognition of the prevalence, impact and the relativity of the definitions used in current literature is an important prerequisite for health care providers in their management of MUS. Indeed, the prevalence of MUS is highly dependent on the case definitions used. All definitions are syndromal and have the character of a checklist approach. This is illustrated by the classification of a multi-setting population of patients with MUS into either DSM IV somatization (undifferentiated somatoform and pain) disorder versus DSM V somatic symptom disorder (SDD) [6]. In a questionnaire study involving baseline data of 325 MUS patients in 1st, 2nd and 3rd lines of health care, DSM V SSD criteria proved more restrictive, as only 45.5 % fulfilled these criteria while 92.9 % of participants were included using the DSM IV criteria. DSM V SSD and the presence of psychologic criteria selected for more symptom severity and physical dysfunction in MUS. With chronification the semantic discussion remains, as exemplified in the review of De Gucht et al. 2002, proposing a distinction into presenting somatization secondary to psychological distress versus a primary phenomenon characterized by the presence of MUS (functional somatization). More recently, literature has moved away from this labeling approach and focused on functional limitations and possibly on different phenotypes that may be relevant for differential effects of illness on disability. Furthermore there is considerable overlap between the definitions of the different functional somatic syndromes [23, 24].
Whatever the limitations and the semantics of syndromal definitions, patients frequently present in primary care with multiple somatic complaints, that can be associated with significant distress and functional impairment. These can become chronic in 20 to 25 % of cases, associated with high use of medical services and increased risk of iatrogenic complications [9]. In a point prevalence primary care study, GP’s assessed presenting complaints as unexplained in 13 % of consecutive at random consultations [35]. In a large scale questionnaire survey of morbidity in 400.000 patients aged 18 years and older and visiting their GP at least once a year in 104 general practices in the Netherlands, 25-50 % of all reasons for a GP visit concerned medically unexplained symptoms, 20 % of GP-patient contacts physical symptoms without a pathological explanation. However, the frequent presentation of such symptoms within the same individual is significantly rarer: only 2.45 % presented at least 4 times in a single year period with symptoms considered medically unexplained and lacking a medical diagnosis. Socio-demographically these patients were significantly older, more often female, less educated, more frequently unemployed and more frequently of a non-Western origin than “average” patients or patients with a medical diagnosis [36].
These patients also represent a considerable burden in acute care. In a retrospective chart study of 2869 adult patients at three tertiary care emergency departments (ED) MUS were present in 13.4 % of all ED admissions, and in 18.5 % of patients, after exclusion of trauma. Patients with MUS on the ED were more often younger, female, self-referred and frequent visitors and more often had psychiatric disease. Dutch and Belgian hospitals differed in the distribution of patients in triage categories and the incidence of psychiatric illnesses. Hence, patients with MUS represent a major burden to ED’s, as in primary and secondary healthcare [2]. In an older retrospective cohort study in secondary care, the proportion of MUS in frequent attenders represented 54 % in gastroenterology, 50 % in neurology, 34 % in cardiology, 33 % in rheumatology, 30 % in orthopedic clinics, 27 % in otorhinolaryngology and even 17 % in general surgery and gynecology and 15 % in pulmonary medicine [27]. Hence, they represent a significant segment of medical activity and are transversally relevant in most domains. A cross-sectional survey in two London general hospitals estimated the prevalence and risk factors for MUS across a variety of specialties; about half of the respondents from seven outpatient clinics fulfilled criteria for MUS, representing the most common diagnosis in some specialties with the highest prevalence in the gynaecology clinic (66 %). After adjustment for confounders, MUS were associated with female gender, younger age and current employment. Psychiatric comorbidity was not associated per se with the presence of MUS but was more likely in patients with multiple symptoms [23, 24].
In a review on somatization in refugees in non-Western countries [29] the prevalence of somatization disorder was shown to be equal in different refugee populations world-wide. The number of MUS is generally higher among refugees as compared to non-refugees, but studies are not comparable, as different definitions of somatization were used, such as in clinical assessments and conclusions from questionnaires. Somatization in refugees is strongly connected with psychopathology and possibly with traumatization and with negative life events and might be perceived as a specific idiom of distress, which accompanies PTSD. Hence, refugee populations require specific screening for clinical PTSD. Kounou et al, 2017 explored the relationship between peritraumatic reactions, PTSD symptoms, somatization and quality of life in a retrospective, cross-sectional study of a large sample of 101 adult refugees (45 % of the female gender) 2 years after the 2011 Ivory Coast sociopolitical crisis. They demonstrated that 86,1 % of participants scored above the threshold for probable clinical PTSD. Peritraumatic dissociation and stress were significantly associated with PTSD symptoms. Somatization and PTSD symptoms negatively correlated with quality of life. [19].