Comparison between an empirically derived model and the EuroSCORE system in the evaluation of hospital performance: the example of the Italian CABG Outcome Project.
OBJECTIVE
To compare the risk-adjustment model empirically derived from the 'Italian CABG Outcome Project' with that of the additive and logistic EuroSCORE in terms of accuracy, predictive power and ability to rank hospital performances.


METHODS
The Italian CABG model, the logistic and additive EuroSCORE were applied to the Italian CABG population; the observed deaths/expected deaths (O/E) ratios, as obtained by the three models, were computed for each Italian cardiac surgery centre and for six classes of risk-stratified patients. The performance of the three models in predicting the 30-day mortality was formally assessed for calibration (Hosmer-Lemeshow test) and discrimination (ROC area). According to the three models, risk-adjusted mortality rates (RAMR = O/E x Italian CABG population mortality rate) were estimated for each centre; possible differences were detected in the identification of hospitals with mortality rates higher and lower than average.


RESULTS
The Italian CABG model uses fewer variables than the EuroSCORE system (14 vs 17) and exhibits the best performance in terms of discrimination and calibration. Contrary to the other tested models, the logistic EuroSCORE shows a significant Hosmer-Lemeshow test (chi(H-L)(2)=19.30, p<0.0001), indicating unsatisfactory calibration, and a clear predicted death overestimation in each of the considered risk classes (O/E = 0.4). When a proper recalibration procedure is applied, the logistic EuroSCORE performance parameters achieve acceptable levels. The Italian CABG model identified seven centres as having higher than average mortality, while the EuroSCORE identified the same seven centres plus one other. The Italian CABG model identified eight centres with lower than average mortality, five of which were identified by the additive EuroSCORE and four of which were identified by the logistic EuroSCORE. The additive EuroSCORE identified four more and the logistic EuroSCORE three more low mortality centres.


CONCLUSIONS
Although this analysis reveals a satisfactory concordance between results from the three models, a detailed comparison shows that the Italian CABG model uses fewer variables and performs better than the others. Nevertheless, when properly recalibrated, the EuroSCORE model can be exported to the Italian population and used to rank hospital performance and evaluate preoperative risk of patients undergoing open-heart surgery.
D'Errigo
Paola
P
National Centre of Epidemiology, Surveillance and Health Promotion - Istituto Superiore di Sanità, Rome, Italy. paola.derrigo@iss.it
Seccareccia
Fulvia
F
Rosato
Stefano
S
Manno
Valerio
V
Badoni
Gabriella
G
Fusco
Danilo
D
Perucci
Carlo A
CA
D000328:Adult; D000368:Aged; D001026:Coronary Artery Bypass / Q000401:mortality*; D005260:Female; D017052:Hospital Mortality; D006779:Hospitals, Public / Q000592:standards*; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D017063:Outcome Assessment, Health Care / Q000379:methods*; D018570:Risk Assessment / Q000379:methods