The Hospital Compare Mortality Model and the Volume–Outcome Relationship

Authors

  • Jeffrey H. Silber,

    1. Center for Outcomes Research, 3535 Market Street, Suite 1029, Philadelphia, PA 19104
    2. Department of Anesthesiology & Critical Care, University of Pennsylvania School of Medicine, Philadelphia, PA
    3. Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA
    4. Department of Health Care Management, The Wharton School, University of Pennsylvania, Philadelphia, PA
    5. Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia, PA
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    • Address correspondence to Jeffrey H. Silber, M.D., Ph.D., Center for Outcomes Research, 3535 Market Street, Suite 1029, Philadelphia, PA 19104; e-mail: silberj@wharton.upenn.edu. Tanguy J. Brachet, Ph.D., Richard N. Ross, M.S., Laura J. Bressler, B.A., Orit Even-Shoshan, M.S., and Scott A. Lorch, M.D., M.S.C.E., are with the Center for Outcomes Research, The Children's Hospital of Philadelphia, Philadelphia, PA. Jeffrey H. Silber, M.D., Ph.D., and Tanguy J. Brachet, Ph.D., are with the Department of Anesthesiology & Critical Care, University of Pennsylvania School of Medicine, Philadelphia, PA. Jeffrey H. Silber, M.D., Ph.D., is with the Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA. Jeffrey H. Silber, M.D., Ph.D., and Kevin G. Volpp, M.D., Ph.D., are with the Department of Health Care Management, The Wharton School, University of Pennsylvania, Philadelphia, PA. Jeffrey H. Silber, M.D., Ph.D., Paul R. Rosenbaum, Ph.D., Tanguy J. Brachet, Ph.D., Orit Even-Shoshan, M.S., Scott A. Lorch, M.D., M.S.C.E., and Kevin G. Volpp, M.D., Ph.D., are with the Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia, PA. Paul R. Rosenbaum, Ph.D., is with the Department of Statistics, The Wharton School, University of Pennsylvania, Philadelphia, PA. Scott A. Lorch, M.D., M.S.C.E., is with the Department of Pediatrics, Division of Neonatology, The Children's Hospital of Philadelphia, Philadelphia, PA. Kevin G. Volpp, M.D., Ph.D., is with the Center for Health Equity Research and Promotion, Veteran's Administration Hospital, Philadelphia, PA. Kevin G. Volpp, M.D., Ph.D., is with the Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA.

  • Paul R. Rosenbaum,

    1. Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia, PA
    2. Department of Statistics, The Wharton School, University of Pennsylvania, Philadelphia, PA
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  • Tanguy J. Brachet,

    1. Center for Outcomes Research, The Children's Hospital of Philadelphia, Philadelphia, PA
    2. Department of Anesthesiology & Critical Care, University of Pennsylvania School of Medicine, Philadelphia, PA
    3. Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia, PA
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  • Richard N. Ross,

    1. Center for Outcomes Research, The Children's Hospital of Philadelphia, Philadelphia, PA
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  • Laura J. Bressler,

    1. Center for Outcomes Research, The Children's Hospital of Philadelphia, Philadelphia, PA
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  • Orit Even-Shoshan,

    1. Center for Outcomes Research, The Children's Hospital of Philadelphia, Philadelphia, PA
    2. Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia, PA
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  • Scott A. Lorch,

    1. Center for Outcomes Research, The Children's Hospital of Philadelphia, Philadelphia, PA
    2. Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia, PA
    3. Department of Pediatrics, Division of Neonatology, The Children's Hospital of Philadelphia, Philadelphia, PA
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  • Kevin G. Volpp

    1. Department of Health Care Management, The Wharton School, University of Pennsylvania, Philadelphia, PA
    2. Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia, PA
    3. Center for Health Equity Research and Promotion, Veteran's Administration Hospital, Philadelphia, PA
    4. Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA
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Abstract

Objective. We ask whether Medicare's Hospital Compare random effects model correctly assesses acute myocardial infarction (AMI) hospital mortality rates when there is a volume–outcome relationship.

Data Sources/Study Setting. Medicare claims on 208,157 AMI patients admitted in 3,629 acute care hospitals throughout the United States.

Study Design. We compared average-adjusted mortality using logistic regression with average adjusted mortality based on the Hospital Compare random effects model. We then fit random effects models with the same patient variables as in Medicare's Hospital Compare mortality model but also included terms for hospital Medicare AMI volume and another model that additionally included other hospital characteristics.

Principal Findings. Hospital Compare's average adjusted mortality significantly underestimates average observed death rates in small volume hospitals. Placing hospital volume in the Hospital Compare model significantly improved predictions.

Conclusions. The Hospital Compare random effects model underestimates the typically poorer performance of low-volume hospitals. Placing hospital volume in the Hospital Compare model, and possibly other important hospital characteristics, appears indicated when using a random effects model to predict outcomes. Care must be taken to insure the proper method of reporting such models, especially if hospital characteristics are included in the random effects model.

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