Prediction of clinical outcome in patients with non-ST-elevation acute coronary syndrome (NSTE-ACS) using the TIMI risk score extended by N-terminal pro-brain natriuretic peptide levels.

BACKGROUND: N-terminal pro-brain natriuretic peptide (Nt-proBNP) is a strong independent predictor of death in acute coronary syndromes. In order to improve risk assessment in patients with unstable coronary artery disease we investigated the role of the additional determination of Nt-proBNP levels in patients sub-grouped into high-, medium- and low-risk groups according to the TIMI risk score.

METHODS: Nt-proBNP was determined in 145 consecutive patients admitted to our clinic with typical anginal pain in the past 24 hours and normal left ventricular function. Using classification and regression tree analysis, we investigated whether Nt-proBNP levels provide clinically relevant prognostic information in addition to the TIMI risk score. Nt-proBNP concentrations were determined using a commercially available assay from Biomedica, Austria. The normal range of this assay is <2827 pg/ml.

RESULTS: Multivariate logistic regression analysis revealed that TIMI scores and Nt-proBNP levels are independent predictors of mortality (P = 0.001 and P < 0.001, respectively). Patients with Nt-proBNP levels >5225 pg/ml had the highest mortality rate, independent of their TIMI risk classification. In the subset of patients with Nt-proBNP < or =5225 pg/ml, patients at TIMI medium risk but with Nt-proBNP above 2827 pg/ml had significantly higher mortality than patients with lower levels of Nt-proBNP (P = 0.03). Accordingly, we developed a combined risk score consisting of four risk groups: very high (Nt-proBNP > or =5225 pg/ml), high (TIMI high-risk group or TIMI medium-risk group and Nt-proBNP >2827 pg/ml), medium (TIMI medium-risk group and Nt-proBNP < or =2827 pg/ml) and low (TIMI low-risk group). The area under the receiver operating characteristic curve was 0.772 for the TIMI score alone and 0.863 for the combined risk score (P < 0.001).

CONCLUSION: Determination of plasma Nt-proBNP levels and incorporation of these into TIMI risk classification by creating a combined risk score significantly improves risk assessment of patients with unstable coronary artery disease.