ASSESSING THE OUTCOMES OF CORONARY-ARTERY BYPASS GRAFT-SURGERY - HOW MANY RISK-FACTORS ARE ENOUGH

Objectives. We sought to determine whether more comprehensive risk-adj ustment models have a significant impact on hospital risk-adjusted mor tality rates after coronary artery bypass graft surgery (CABG) in Onta rio, Canada, Background. The Working Group Panel on the Collaborative CABG Database Project has categorized 44 clinical variables into 7 cor e, 13 level 1 and 24 level 2 variables, to reflect their relative impo rtance in determining short-term mortality after CABG. Methods. Using clinical data for all 5,517 patients undergoing isolated CABG in Ontar io in 1993, we developed 12 increasingly comprehensive risk-adjustment models using logistic regression analysis of 6 of the Panel's core va riables and 6 of the Panel's level 1 variables, We studied how the ris k adjusted mortality rates of the nine cardiac surgery hospitals in On tario changed as more variables were included in these models, Results . Incorporating six of the core variables in a risk-adjustment model l ed to a model with an area under the receiver operating characteristic (ROC) curve of 0.77, The ROC curve area slightly improved to 0.79 wit h the inclusion of six additional level 1 variables (p = 0.063), Hospi tal risk-adjusted mortality rates and relative rankings stabilized aft er adjusting for six core variables, Adding an additional six level 1 variables to a risk adjustment model had minimal impact on overall res ults, Conclusions. A small number of core variables appear to be suffi cient for fairly comparing risk-adjusted mortality rates after CABG ac ross hospitals in Ontario, For efficient interprovider comparisons, ri sk-adjustment models far CABG could be simplified so that only essenti al variables are included in these models, (C) 1997 by the American Co llege of Cardiology.