A Study On The Operability Of The Diagnostic Criteria For Somatic Disorder

Backgrounds:Somatic symptom disorder(SSD)has been one of the most common headaches in every clinical departments.SSD patients bothered by various somatic symptoms throughout years tend to pay frequent visits to different medical settings,which not only leads to deteriorated quality of life and impaired social functions,but also result in improper utilization of public health resources.Therefore,it is of considerable significance to effectively detect SSD among patients complaining of somatic symptoms and take early interventions accordingly.In order to improve diagnostic validity and clinical applicability,DSM-5 employs a revised inclusive diagnostic approach,in which organic causes of somatic symptoms are no longer required as exclusion criteria,while positive psycho-behavioral features related to somatic symptoms and health concerns are considered crucial and included as the B criteria.Currently,no consensus has been reached on the best quantitative assessment tool for B criteria.Somatic Symptom Disorder B-criteria Scale(SSD-12)has been developed by Toussaint et al.to evaluate B criteria,and excellent psychometric properties have been strictly validated among the German populations.A Chinese version of SSD-12 is now available,and its reliability,validity and usefulness have not yet been verified among the Chinese populations.Objectives:Our study aims to 1)verify the reliability and validity of SSD-12 in the Chinese population;2)describe the clinical features of SSD patients in China;3)investigate the proportion of SSD among Chinese tertiary general hospital outpatients.Methods:Participants were recruited by convenient sampling from outpatient departments of gastroenterology,traditional Chinese medicine(TCM)and psychology of Peking Union Medical College Hospital.After signing informed consent,they filled out a battery of questionnaires including SSD-12,PHQ-15,PHQ-9,GAD-7,WI-8,SSS-8,WHO DAS 2.0,and SF-12.Then researchers conducted two structured interviews using M.I.N.I.and SCID-5-RV to diagnose SFD and SSD respectively.2 weeks later,over 20%of participants were retested on the SSD-12 scale.Results:1.Item characteristics:Critical ratio of each item ranged from 5.92 to 14.18,reflecting an acceptable range of item difficulty and favorable discrimination.Each item score showed moderate to high correlations with the sum score(r=0.63-0.88),indicating that all items were supportive towards the whole questionnaire.2.Reliability:1)Split-half reliability:Spearman-Brown split-half coefficient=0.949.2)Internal consistency:Cronbach a =0.949.3)Test-retest reliability:interclass correlation coefficient(ICC)=0.987.2.Validity:1)Construct validity:A three-factorial structure reflecting the three psychological subcriteria interpreted as cognitive,affective,and behavioral aspects,was supported by confirmatory factor analysis,while a general factor model was also justified.2)Criterion-related validity:score of SSD-12 was closely correlated with that of WI-8(r=0.80),closely to moderately related with those of PHQ-9 and GAD-7(r=0.63-0.65),and moderately correlated with that of PHQ-15(r=0.50).3.Cut-off value:when using SCID-5-RV as the gold standard,area under the curve(AUC)of SSD-12 score=0.927,with 16 as its optimal cut-off value.Sensitivity=0.806,specificity=0.917,and 88.3%would be correctly diagnosed.When WI-8 was evaluated as a diagnostic test,its AUC=0.836.When PHQ-15 was evaluated as a diagnostic test,its AUC=0.694.When PHQ-15 and SSD-12 were combined,its AUC=0.920.4.Detection rate:among the 120 participants from three outpatient departments,68(56.7%)were diagnosed as SFD,among whom 0 were diagnosed as somatization disorder while 58(48.3%)were diagnosed as undifferentiated somatoform disorder;36(30.0%)were diagnosed as SSD.Agreement between these two diagnoses was low(Cohen k=0.335).5.Clinical features of SSD patients:compared with patients with only SFD or patients with neither diagnosis,patients with SSD scored significantly higher in PHQ-15,DAS 2.0,PHQ-9,GAD-7,WI-8,SSD-12 and SSS-8,and scored significantly lower in MCS and PCS.Compared with non-SSD patients,SSD patients received more treatment in the past 6 months,and were less satisfied with their treatment;SSD patients suffered from more persistent symptoms and visited hospitals more frequently in the past 12 months.6.Disability and life quality:We found PHQ-9 score as a significant predictive factor of disability,with 57.5%of total variance explained by this equation.SSD-12 and PHQ-15 scores were found as significant predictive factors of PCS,with 34.7%of total variance explained by this equation.SSD-12 score,PHQ-9 score and somatic symptom durations were found as significant predictive factors of MCS,with 61.6%of total variance explained by this equation.7.The age and proportion of treatment in the past 6 months of patients from gastroenterology department were higher than those from TCM and psychology departments.No significant difference were found among SSD patients from these three departments in treatment satisfaction,somatic symptom duration,medical visits in the past 12 months,somatic symptom burden,level of anxiety,depression,health anxieties and illness beliefs,degree of disability or physical and mental quality of life.Conclusions:1.The Chinese version of SSD-12 demonstrated satisfactory reliablities and validities among Chinese tertiary general hospital outpatients.This suggested that SSD-12 could be employed as a useful tool to quatitatively evaluate the cognitive,affective and behavioraldeviations related to somatic symptoms in Chinese outpatient clinical settings.Future studies should evaluate the responsiveness of SSD-12 to treatment as well as its feasibilities as a screening tool in different clinical settings in China.2.SSD-12 showed better performance than WI-8 on the operationalization of B criteria.For quick screening of SSD at clinical settings,we recommend utilization of SSD-12,with 16 as the cut-off value.For severity specification,we recommend combined utilization of PHQ-15 and SSD-12.3.The detection rate of SSD was 30.0%among outpatients fromdepartments of gastroenterology,TCM,and psychology in a Chinese tertiary hospital,while the detection rate of SFD was 56.7%.Agreement between these two diagnoses was low.4.Compared to patients with only SFD,patients with SSD showed heavier somatic symptom burders,higher levels of anxiety,depression,health anxieties and illness beliefs,higher degrees of disabilities,and poorer physical and mental life qualities.5.Psycho-behavioral reactions associated with physical symptoms were significant predictive factors of both physical and mental life qualities for outpatients presented with somatic symptoms.Recognition and adjustment of pathological cognitions,proper interventions towards comorbid anxieties or depressions,and management of illness behavior could be helpful for improving the life qualities of SSD patients.