The Trade-off Between Costs and Quality of Care in the Treatment of Psychosomatic Patients with Somatoform Pain Disorder

The inclusion criteria for patient selection (n = 101) were (i) a main diagnosis of somatoform pain disorder according to International Classification of Diseases-10 (ICD-10) [F45.4, F45.40, F45.41]; (ii) complete data on the mental component summary reflecting overall functioning of mental health (MCS-8) measured with the Short Form-8 Health Survey (SF-8) within 3 days of the admission and discharge dates; and (iii) treatment at Charité Universitaetsmedizin (Berlin, Germany) during the period January 2006–June 2010. The change in the MCS-8 score incurred over the treatment period was used as an indicator of quality of care. Treatment costs were calculated from the provider’s perspective, mainly using bottom-up micro-costing. The year of valuation for cost calculation was 2008 (with no inflation adjustment); for costs provided by the accounting department for services consumed by the patient, the valuation year was based on the year of service provision. We hypothesized that the outcome ‘change in MCS-8 score’ was a function of the independent variable costs, patient characteristics, socio-demographic variables, pain-related variables, co-morbidities and subjective illness attribution, i.e. whether patients attributed the origin of pain mainly to a somatic cause or not. An interaction term between costs and illness attribution was included to control for the hypothesized differing effects of resource input or costs on the outcome variable conditional on patients’ illness attribution. Hausman tests indicated that endogeneity was not present, thus, ordinary least squares regression (OLS) was conducted. We assessed whether the change in the MCS-8 score was clinically meaningful and perceptible by the patient, using the minimal clinical important difference (MCID). For Short Form Health Surveys, the MCID for changes in the mental component summary is typically around 3 points.