Performance of substance use disorder treatment systems: The effect of case-mix adjustment

Aims: Transitional care between detoxification (detox) and rehabilitation in either residential or outpatient settings prevents detox readmissions and reduces patients’ risk of death due to accidental overdose. As state agencies seek to evaluate local treatment systems on their performancewith transitional care for detox patients, it is important to assess the effect of case-mix adjustment on performance outcomes. Methods: Admissions data on all detox patients from 32 counties in California were abstracted from the California Outcomes Measurement System for 2008–2009 (N=24,928). Counties were ranked based on the proportion of detox patients transferred to any form of treatment within 14 days of discharge from a detox service. Case-mix adjusterswere identified by examining their predictive power in a series of binarymixedmodels. Adjusted rankings were based on the mean predicted probability of a detox transfer for each county. A Kendall’s tau coefficientwas used to evaluate the impact of adjustment on county rankings. Results: Important case-mix adjusters included Medi-Cal coverage, stable living situation, criminal justice referral to treatment, high school education, primary drug problem, prior treatment, lifetime mental illness diagnosis, and receipt of medication during treatment. The impact of case-mix adjustment on the county rankingswasminimal (Kendall’s tau= .9758), but it affected the relative rankings of 11 counties. Conclusions: This study represents a first step in exploring the utility of case-mix adjustment for monitoring county-wide performance in transitional care for detox patients. Case-mix adjustment with CalOMS data has minimal impact on county rankings. Subsequent analyses will examine the role of county-level factors on transitional care performance such as county size, number of treatment programs, and funding levels. Financial support: Kirschstein-NRSA award (NIDA 5F31DA031509-01); State of California/Department of Alcohol and Drug Programs Evaluation Services to Enhance the Data Management System in California.