Aim: To evaluate the method for comparison of average length of stay in hospitals as defined in a contract between German health insurance companies and the „Deutsche Krankenhausgesellschaft” (German Hospital Association).
Method: Simulation study executing the algorithm agreed upon in different scenarios, which varied the number of hospitals to be compared, the dispersion of diagnostic specialization over hospitals, and the distribution of hospitals’ sizes. Scenarios were constructed to realistically reflect the situation in German inpatient treatment of mentally ill patients.
Results: By fixing casemix adjustments only on diagnoses of patients and by doing so aggregated on the level of hospitals, the method for comparison yielded artificial differences between hospitals even in a situation where each patient is treated with exactly the same amount of resource allocation (given the individual needs defined for all scenarios). Results of artificial differences were heavily biased against or in favour of the reference hospitals according to the specific condition of the scenario parameters.
Conclusion: The contracted method is not capable of achieving fair hospital comparisons, at least not for psychiatric hospitals.