Zur Strategieanfälligkeit der Arzneimittelkomponente des IPHCC+RxGroups-Klassifikationssystems in einem morbiditätsorientierten Risikostrukturausgleich - Eine konzeptionelle und datengestützte Analyse

Background: A report commissioned by the German Ministry of Health recommends to the existing scheme for calculating risk-adjusted transfers to sickness funds supplement with the IPHCC+RxGroups method. The method is based on inpatient diagnoses and prescribed drugs as health status measures deduced from prior use. Objective: The present study investigates the sickness fund's expected net return from gaming based on the drug component of the risk adjuster. Methods: The study explores three possible strategies using the RxGroups method. For the stimulations, insurees are assigned to additional indications or to higher valued RxGroups within the same indication. Then, costs and financial benefits attributable to the altered drug use are estimated and compared with the status quo. The study uses 2000 and 2001 sample data of more than 370,000 insurees of Germany's company-based sickness funds system (BKK). Results: While upgrading increases overall costs, it can be beneficial for the individual sickness funds. Their net return crucially depends on the number of sickness funds gaming the system: the more participating in the game, the smaller is the average net return. Moreover, not participating often is even worse, which in turn points to a prisoner's dilemma. Conclusions: When extending the risk adjustment scheme in social health insurance, the German legislator should take into account the perverse incentives of risk adjusters such as the described prescription drug model.