Use of B-type natriuretic peptide in the risk stratification of community-acquired pneumonia

BACKGROUND: Community-acquired pneumonia (CAP) is the leading infectious cause of death in developed countries. Risk stratification has previously been difficult. METHODS: Markers of cardiac stress (B-type natriuretic peptide, BNP) and inflammation (C-reactive protein, white blood cell count, procalcitonin) as well as the pneumonia severity index (PSI) were determined in 302 consecutive patients presenting to the emergency department (ED) with CAP. The accuracy of these parameters to predict death was evaluated as the primary endpoint. Prediction of treatment failure was considered as the secondary endpoint. RESULTS: B-type natriuretic peptide levels increased with rising disease severity as classified by the PSI (P = 0.015). BNP levels were significantly higher in nonsurvivors compared to survivors [median 439.2 (IQR 137.1-1384.6) vs. 114.3 (51.3-359.6) pg mL(-1), P > 0.001]. In a receiver operating characteristic analysis for the prediction of survival the area under the curve (AUC) for BNP was comparable to the AUC of the PSI (0.75 vs. 0.71, P = 0.52). Importantly, the combination of BNP and the PSI significantly improved the prognostic accuracy of the PSI alone (AUC 0.78 vs. 0.71; P = 0.02). The optimal cut-off for BNP was 279 pg mL(-1). The accuracy of BNP to predict treatment failure was identical to the accuracy to predict death (AUC 0.75). CONCLUSIONS: In patients with CAP, BNP levels are powerful and independent predictors of death and treatment failure. When used in conjunction with the PSI, BNP levels significantly improve the risk prediction when compared with the PSI alone.