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Health Serv Res. 1997 February; 31(6): 755–771.
PMCID: PMC1070157

Does case mix matter for substance abuse treatment? A comparison of observed and case mix-adjusted readmission rates for inpatient substance abuse treatment in the Department of Veterans Affairs.


OBJECTIVE: To develop a case mix model for inpatient substance abuse treatment to assess the effect of case mix on readmission across Veterans Affairs Medical Centers (VAMCs). DATA SOURCES/STUDY SETTING: The computerized patient records from the 116 VAMCs with inpatient substance abuse treatment programs between 1987 and 1992. STUDY DESIGN: Logistic regression was used on patient data to model the effect of demographic, psychiatric, medical, and substance abuse factors on readmission to VAMCs for substance abuse treatment within six months of discharge. The model predictions were aggregated for each VAMC to produce an expected number of readmissions. The observed number of readmissions for each VAMC was divided by its expected number to create a measure of facility performance. Confidence intervals and rankings were used to examine how case mix adjustment changed relative performance among VAMCs. DATA COLLECTION/EXTRACTION METHODS: Ward where care was provided and ICD-9-CM diagnosis codes were used to identify patients receiving treatment for substance abuse (N = 313,886). PRINCIPAL FINDINGS: The case mix model explains 36 percent of the observed facility level variation in readmission. Over half of the VAMCs had numbers of readmissions that were significantly different than expected. There were also noticeable differences between the rankings based on actual and case mix-adjusted readmissions. CONCLUSIONS: Secondary data can be used to build a reasonably stable case mix model for substance abuse treatment that will identify meaningful variation across facilities. Further, case mix has a large effect on facility level readmission rates for substance abuse treatment. Uncontrolled facility comparisons can be misleading. Case mix models are potentially useful for quality assurance efforts.

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Selected References

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  • Babor TF, Dolinsky Z, Rounsaville B, Jaffe J. Unitary versus multidimensional models of alcoholism treatment outcome: an empirical study. J Stud Alcohol. 1988 Mar;49(2):167–177. [PubMed]
  • Booth BM, Yates WR, Petty F, Brown K. Patient factors predicting early alcohol-related readmissions for alcoholics: role of alcoholism severity and psychiatric co-morbidity. J Stud Alcohol. 1991 Jan;52(1):37–43. [PubMed]
  • Cook CA, Booth BM, Blow FC, Gogineni A, Bunn JY. Alcoholism treatment, severity of alcohol-related medical complications, and health services utilization. J Ment Health Adm. 1992 Spring;19(1):31–40. [PubMed]
  • Fleming C, Fisher ES, Chang CH, Bubolz TA, Malenka DJ. Studying outcomes and hospital utilization in the elderly. The advantages of a merged data base for Medicare and Veterans Affairs hospitals. Med Care. 1992 May;30(5):377–391. [PubMed]
  • Hadorn DC, Draper D, Rogers WH, Keeler EB, Brook RH. Cross-validation performance of mortality prediction models. Stat Med. 1992 Feb 28;11(4):475–489. [PubMed]
  • Hanley JA, McNeil BJ. The meaning and use of the area under a receiver operating characteristic (ROC) curve. Radiology. 1982 Apr;143(1):29–36. [PubMed]
  • Kent S, Yellowlees P. Psychiatric and social reasons for frequent rehospitalization. Hosp Community Psychiatry. 1994 Apr;45(4):347–350. [PubMed]
  • McLellan AT, Luborsky L, Woody GE, O'Brien CP, Druley KA. Predicting response to alcohol and drug abuse treatments. Role of psychiatric severity. Arch Gen Psychiatry. 1983 Jun;40(6):620–625. [PubMed]
  • Moos RH, Mertens JR, Brennan PL. Rates and predictors of four-year readmission among late-middle-aged and older substance abuse patients. J Stud Alcohol. 1994 Sep;55(5):561–570. [PubMed]
  • Ornstein P, Cherepon JA. Demographic variables as predictors of alcoholism treatment outcome. J Stud Alcohol. 1985 Sep;46(5):425–432. [PubMed]
  • Peterson KA, Swindle RW, Phibbs CS, Recine B, Moos RH. Determinants of readmission following inpatient substance abuse treatment: a national study of VA programs. Med Care. 1994 Jun;32(6):535–550. [PubMed]
  • Smith DW, McFall SL, Pine MB. State rate regulation and inpatient mortality rates. Inquiry. 1993 Spring;30(1):23–33. [PubMed]
  • Snowden LR, Holschuh J. Ethnic differences in emergency psychiatric care and hospitalization in a program for the severely mentally ill. Community Ment Health J. 1992 Aug;28(4):281–291. [PubMed]
  • Strauss GD, Sack DA, Lesser I. Which veterans go to VA psychiatric hospitals for care: a pilot study. Hosp Community Psychiatry. 1985 Sep;36(9):962–965. [PubMed]
  • Watt DC, Szulecka TK. The effect of sex, marriage and age at first admission on the hospitalization of schizophrenics during 2 years following discharge. Psychol Med. 1979 Aug;9(3):529–539. [PubMed]

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