Conceptual and methodological issues in the comparison of inpatient psychiatric facilities.

The authors compared the length of stay of acute admission patients at a mental health center and a nearby state hospital. The two facilities had significantly different length of stay distributions; the mean was not an adequate index to describe these patterns. Despite careful matching, patients at the state hospital were more disabled. Different patient characteristics were associated with length of stay at the two facilities, and these were also characteristics on which the patient populations differed at admission. The authors conclude that comparisons of hospitals, for example, on mean or median length of stay can be misleading unless the different functions, policies, and constraints of the facilities are taken into account.