Risk scores for risk stratification in acute coronary syndromes: useful but simpler is not necessarily better

Abstract

Our objectives were (i) to compare the discriminatory performance of the Thrombolysis in Myocardial Infarction risk score (TIMI RS), Platelet glycoprotein IIb/IIIa in Unstable angina: Receptor Suppression Using Integrilin Therapy risk score (PURSUIT RS), and Global Registry of Acute Cardiac Events risk score (GRACE RS) for in-hospital and 1 year mortality across the broad spectrum of non-ST-elevation acute coronary syndromes (ACS) and (ii) to determine their incremental prognostic utility beyond overall risk assessment by physicians. We calculated the TIMI RS, PURSUIT RS, and GRACE RS for 1,728 patients with non-ST-elevation ACS in the prospective, multicentre, Canadian ACS II Registry. Discriminatory performance was measured by the c-statistic (area under receiver-operating characteristic curve) and compared by the method described by DeLong. TIMI RS, PURSUIT RS, and GRACE RS all demonstrated good discrimination for in-hospital death (c-statistics = 0.68, 0.80, 0.81, respectively, all P < 0.001) and 1 year mortality (c-statistics = 0.69, 0.77, 0.79, respectively, all P < 0.0001). However, PURSUIT RS and GRACE RS performed significantly better than the TIMI RS in predicting in-hospital (P = 0.036 and 0.02, respectively) and 1 year (P = 0.006 and 0.001, respectively) outcomes. In multivariable analysis adjusting for the use of in-hospital revascularization, stratification by tertiles of risk scores (into low, intermediate, and high-risk groups) furnished independent and greater prognostic information compared with risk assessment by treating physicians for 1 year outcome. Compared with TIMI RS, both PURSUIT RS and GRACE RS allow better discrimination for in-hospital and 1 year mortality in patients presenting with a wide range of ACS. All three risk scores confer additional important prognostic value beyond global risk assessment by physicians. These validated risk scores may refine risk stratification, thereby improving patient care in routine clinical practice.