Eur J Cardiothorac Surg 2000 Dec;18(6):703-10
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Intra-institutional prediction of outcome after cardiac
surgery: comparison between a locally derived model and the EuroSCORE.
Pitkanen O, Niskanen M, Rehnberg S, Hippelainen M, Hynynen M.
Department of Anaesthesiology and Intensive Care, Kuopio University
Hospital, FIN-70210, Kuopio, Finland. firstname.lastname@example.org
OBJECTIVE: To construct models for predicting mortality, morbidity and
length of intensive care unit (ICU) stay after cardiac surgery and to
compare the performance of these models with that of the EuroSCORE in two
independent validation databases. METHODS: Clinical data on 4592 cardiac
surgery patients operated between 1992 and 1996 were retrospectively
collected. In order to derive predictive models and to validate them, the
patient population was randomly divided into a derivation database (n=3061)
and a validation database (n=1531). Variables that were significant in
univariate analyses were entered into a backward stepwise logistic
regression model. The outcome was defined as mortality within 30 days after
surgery, predefined morbidity, and the length of ICU stay lasting >2
days. In addition to the retrospective database, the models were validated
also in a prospectively collected database of cardiac surgical patients
operated in 1998-1999 (n=821). The EuroSCORE was tested in two validation
databases, i.e. the retrospective and prospective one. Hosmer-Lemeshow
goodness-of-fit was used to study the calibration of the predictive models.
Area under the receiver operating characteristic (ROC) curve was used to
study the discrimination ability of the models. RESULTS: The overall
mortality in the retrospective and the prospective data was 2 and 1%, and
morbidity 22 and 18%, respectively. The created predictive models fitted
well in the validation databases. Our models and the EuroSCORE were equally
good in discriminating patients. Thus, in the prospective validation
database, the mean areas under the ROC curve for our models and for the
EuroSCORE were similar, i.e. 0.84 and 0.77 for mortality, 0.74 and 0.74 for
morbidity, and 0.81 and 0.79 for the length of intensive care unit stay
lasting for 2 days or more, respectively. CONCLUSIONS: Our models and the
EuroSCORE were equally good in discriminating the patients in respect to
outcome. However, our model provided also well calibrated estimation of the
probability of prolonged ICU stay for each patient. As was originally
suggested, the EuroSCORE may be an appropriate tool in categorizing cardiac
surgical patients into various subgroups in interinstitutional comparisons.
Our models may have additive value especially in resource allocation and
quality assurance purposes for local use.