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The effect of casemix adjustment on mortality as predicted by APACHE II

D R Goldhill1, P S Withington

  • 1Anaesthetics Unit, Royal London Hospital, Whitechapel, UK.

Intensive Care Medicine
|May 1, 1996
PubMed
Abstract

Insights

The APACHE II scoring system did not accurately predict mortality across diverse patient groups in intensive care units. This suggests that using mortality ratios to compare ICUs can be misleading without accounting for patient case mix.

Area of Science:

  • Critical Care Medicine
  • Health Services Research

Background:

  • The APACHE II scoring system is widely used to predict mortality in intensive care units (ICUs).
  • Accurate adjustment for patient case mix is crucial for comparing ICU performance.

Purpose of the Study:

  • To evaluate the effectiveness of APACHE II scoring in adjusting for patient case mix and predicting mortality.
  • To determine if mortality ratios derived from APACHE II scores are reliable for ICU comparisons.

Main Methods:

  • Retrospective analysis of 6258 ICU patients admitted between 1992 and 1994.
  • APACHE II scores were calculated within 24 hours of admission.
  • Observed hospital deaths were compared to predicted deaths using the APACHE II equation.

Main Results:

  • APACHE II predictions showed significant discrepancies with observed mortality across various patient subgroups.
  • Observed deaths exceeded predicted deaths for patients with lower predicted mortality, specific APACHE II score ranges, older age, and certain clinical categories.
  • Mortality ratios were markedly less than 1.0 only for non-operative cardiovascular patients.

Conclusions:

  • APACHE II scoring did not adequately account for case mix variations in this ICU database.
  • Relying on mortality ratios for ICU comparisons without considering case mix differences can lead to inaccurate and misleading conclusions.

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