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Health Serv Res. 1986 February; 20(6 Pt 1): 737–762.
PMCID: PMC1068925

A method for constructing case-mix indexes, with application to hospital length of stay.


This article presents the methodological development of an index for case-mix adjustment of hospital data exemplified by our construction of an index for studying length of stay. We describe the development and evaluation of this index, including internal and external validation procedures, and show an example of its use in a policy-relevant context by applying it to the analysis of length-of-stay differences between investor-owned and voluntary hospitals. Some advantages of this approach to adjusting for case mix are applicability to many hospital or patient output measurements/diagnostic scheme situations; usefulness in reducing heterogeneity in other case-mix adjustments, e.g., the Diagnosis-Related Group (DRG) approach; interpretation possibilities; production of a single score for each patient/hospital; statistical approach allowing more accurate and reliable interpretation of hospital and patient output measurements, ability to deal with hospital deaths; and consideration of the complete set of secondary diagnoses. We also suggest other possible uses of this approach.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Hornbrook MC. Hospital case mix: its definition, measurement and use. Part II: Review of alternative measures. Med Care Rev. 1982 Summer;39(2):73–123. [PubMed]
  • Horn SD, Sharkey PD, Bertram DA. Measuring severity of illness: homogeneous case mix groups. Med Care. 1983 Jan;21(1):14–30. [PubMed]
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  • Quade D, Culver DH, Haley RW, Whaley FS, Kalsbeek WD, Hardison CD, Johnson RE, Stanley RC, Shachtman RH. The SENIC sampling process: design for choosing hospitals and patients and results of sample selection. Am J Epidemiol. 1980 May;111(5):486–502. [PubMed]
  • Freund D, Shachtman RH, Ruffin M, Quade D. Analysis of length-of-stay differences between investor-owned and voluntary hospitals. Inquiry. 1985 Spring;22(1):33–44. [PubMed]
  • Hughes EF, Fuchs VR, Jacoby JE, Lewit EM. Surgical work loads in a community practice. Surgery. 1972 Mar;71(3):315–327. [PubMed]
  • Brodie DC, Smith WE. Constructing a conceptual model of drug utilization review. Hospitals. 1976 Mar 16;50(6):143–passim. [PubMed]

Articles from Health Services Research are provided here courtesy of Health Research & Educational Trust