Principal variable is not what it seems in league tables

doi:10.1136/bmj.322.7295.1181/a

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Robert West, reader in epidemiology

University of Wales College of Medicine, Cardiff CF4 4XN

EDITOR—Sir Brian Jarman's analysis of hospital death rates with “Dr Foster's guide to better health” (Sunday Times) may serve to improve the quality of hospital care—indirectly.1 The principal dependent variable is, however, not what it seems, even after adjustment for age, sex, diagnosis, emergency admission, and length of stay, so that like is not compared with like. Rates derived from hospital episode statistics, deaths per 1000 finished consultant episodes, almost defy interpretation, because the denominators are episodes, not patients. Although this analysis …