Comorbidity of mental disorders in the German G-DRG system effect on length of stay and revenue at a university hospital

Objectives: The effect of comorbid mental disorders on the length of stay and revenue in a DRG system was investigated. Methods: For 33,189 cases of an university hospital (year 2002) the revenue based on a fictitious base rate was calculated, at first with and then without inclusion of diagnosed comorbid mental disorders. Furthermore, the effect of the latter on the length of stay was examined. Results: Renunciation of diagnoses of mental disorders lead to an different DRG grouping in 7.9 % of cases and to a reduction in revenues of about 170.000 EURO. Minimal influence of comorbid mental disorders on the length of stay (R-2 less than or equal to 0.02) could be detected for single diagnostic groups. Conclusions: The lacking influence of comorbid mental disorders on the length of stay in a university hospital is mainly determined by the limited period of inpatient treatment and by the low frequency of diagnosed mental disorders. Therefore, a psychosocial consultation-liaison service is of major importance to guarantee the diagnosis and treatment of a comorbid mental (process quality) disorder and to guarantee adequate revenues in the G-DRG system (quality of structure).