Using national electronic health care registries for comparing the risk of psychiatric re-hospitalisation in six European countries: Opportunities and limitations

Psychiatric re-hospitalisation rates have been of longstanding interest as health care quality metric for planners and policy makers, but are criticized for not being comparable across hospitals and countries due to measurement unclarities. The objectives of the present study were to explore the interoperability of national electronic routine health care registries of six European countries (Austria, Finland, Italy, Norway, Romania, Slovenia) and, by using variables found to be comparable, to calculate and compare re-hospitalisation rates and the associated risk factors. A "Methods Toolkit" was developed for exploring the interoperability of registry data and protocol led pilot studies were carried out. Problems encountered in this process are described. Using restricted but comparable data sets, up to twofold differences in psychiatric re-hospitalisation rates were found between countries for both a 30- and 365-day follow-up period. Cumulative incidence curves revealed noteworthy additional differences. Health system characteristics are discussed as potential causes for the differences. Multi-level logistic regression analyses showed that younger age and a diagnosis of schizophrenia/mania/bipolar disorder consistently increased the probability of psychiatric re-hospitalisation across countries. It is concluded that the advantage of having large unselected study populations of national electronic health care registries needs to be balanced against the considerable efforts to examine the interoperability of databases in cross-country comparisons.