To compare the prognostic significance of blood urea nitrogen (BUN) versus creatinine levels for estimating the risk of death in patients with acute coronary syndrome (ACS).
Methods and results
A prospective study of all patients admitted with suspected (n=1613) and retrospectively confirmed (n=54) myocardial infarction or unstable angina was conducted. The ROC analysis established that the area under the curve for BUN was higher than that of creatinine: 0.76 (95% CI 0.70 to 0.82) and 0.69 (95% CI 0.63 to 0.76), respectively (p=0.005). The threshold level (that maximised the combined sensitivity and specificity) was 8.8 mmol/l for BUN and 110 μmol/l for creatinine. Sensitivity (true positive cases) was 60% and 55% for threshold levels of BUN and creatinine, respectively, and specificity (true negative cases) was 82% and 77%, respectively. An increase of only BUN levels and a combination of increased BUN and creatinine levels, but not isolated hypercreatinaemia, proved to be the independent risk factors of death from ACS. Separate inclusion of BUN and creatinine as continuous variables in the regression model showed that both were associated with the risk of death: OR 1.22 (95% CI 1.17 to 1.28) and 1.016 (95% CI 1.011 to 1.021) per unit increase (R2=14.5 and 8.4%, respectively). When both were simultaneously included, only an increased BUN level was pertinent to the prognosis of ACS: OR after multivariate adjustment 1.17 (95% CI 1.08 to 1.27).
Conclusion
An increased level of BUN is a more significant risk factor for ACS outcomes than that of creatinine.
