Routine outcome monitoring in a public mental health system: the impact of patients who leave care.

OBJECTIVE: An interest exists in using patient outcome data to evaluate the performance of publicly financed mental health organizations. Because patients leave these organizations at a high rate, the impact of patient attrition on routinely collected outcome data was examined.
METHODS: In one county mental health system, routinely collected data on a wide range of outcomes were examined, and a random sample of patients who left treatment was interviewed.
RESULTS: Of the 1,769 patients in ongoing treatment during a one-year period, 554 (31 percent) were lost to follow-up. Among a random sample of 102 patients who left treatment, two had died and 47 were interviewed. Compared with patients who left treatment, patients who stayed were older, more likely to have schizophrenia, less likely to be married, more likely to be living in an institution, more satisfied with their relationships with friends and family, and less likely to have legal problems. Average outcomes improved both for patients who stayed and for patients who left. Patients who left and could be located for follow-up were less severely ill and showed the greatest improvement and the best outcomes. Patients who left and could not be located may have been more severely ill at baseline.
CONCLUSIONS: Outcomes appear to vary substantially by whether patients stay in care and whether they can be located after leaving care. Public mental health systems that wish to evaluate treatment quality using outcome data should attend carefully to which patients are being assessed. Biases can result from convenience sampling and from patients leaving care.