New York's Statistical Model Accurately Predicts Mortality Risk for Veterans Who Obtain Private Sector CABG

Abstract

To determine whether patients' use of the Veterans Health Administration health care system (VHA) is an independent risk factor for mortality following coronary artery bypass grafting (CABG) in the private sector in New York. VHA administrative and New York Department of Health Cardiac Surgery Reporting System (CSRS) databases for surgeries performed in 1999 and 2000. Prospective cohort study comparing observed, expected, and risk-adjusted mortality rates following private sector CABG for 2,326 male New York State residents aged 45 years and older who used the VHA (VHA users) and 21,607 who did not (non-VHA users). We linked VHA administrative databases to New York's CSRS to identify VHA users who obtained CABG in the private sector in New York in 1999 and 2000. Using CSRS risk factors and previously validated risk-adjustment model, we compared patient characteristics and expected and risk-adjusted mortality rates of VHA users to non-VHA users. Compared with non-VHA users, patients undergoing private sector CABG who had used the VHA were older, had more severe cardiac disease, and were more likely to have the following comorbidities associated with increased risk of mortality: diabetes, chronic obstructive pulmonary disease, cerebrovascular disease, peripheral vascular disease, and history of stroke (p<.001 for all); a calcified aorta (p=.009); and a high creatinine level (p=.003). Observed (2.28 versus 1.80 percent) and expected (2.48 versus 1.78 percent) mortality rates were higher for VHA users than for non-VHA users. The risk-adjusted mortality rate for VHA users (1.70 percent; 95 percent confidence interval [CI]: 1.27-2.22) was not statistically different than that for the non-VHA users (1.87 percent; 95 percent CI: 1.69-2.06). Use of the VHA was not an independent risk factor for mortality in the risk-adjustment model. Although VHA users had a greater illness burden, use of the VHA was not found to be an independent risk factor for mortality following private sector CABG in New York. The New York Department of Health risk adjustment model adequately applies to veterans who obtain CABG in the private sector in New York.