Use of N-terminal pro-brain natriuretic peptide to detect cardiac origin in critically ill cancer patients with acute respiratory failure

Objective To assess the accuracy of plasma N-terminal-pro-B-type natriuretic peptide concentrations (NT-proBNP) as a diagnostic tool to recognize acute respiratory failure (ARF) of cardiac origin. Methods Prospective observational study in 100 medical intensive care unit (ICU) patients. NT-proBNP was measured at ICU admission, and diagnosis of cardiac dysfunction was performed using echocardiography. Results Sixteen patients had cardiac ARF, 58 patients had noncardiac ARF, and 26 patients were non-ARF controls. Median (IQR) NT-proBNP was 1,951 (617–9,320) pg/ml and was significantly influenced by the level of renal dysfunction. Patients with noncardiac ARF had higher NT-proBNP [1,912 (704–1,922) pg/ml] than non-ARF patients [1,022 (383–2,613) pg/ml], but lower concentrations than cardiac ARF patients [4,536 (1,568–35,171) pg/ml]. The area under the curve (AUC) was 0.663 ± 0.078 (95% confidence interval 0.510–0.815) and was not significantly influenced by the level of renal dysfunction. In addition, using a stepwise logistic regression model, NT-proBNP failed to predict independently the presence of cardiac dysfunction. However, with specificity and negative predictive value of 100%, a NT-proBNP cutoff value of 500 pg/ml seemed useful to rule out cardiac dysfunction. Indeed, none of the 16 patients with cardiac ARF had a NT-proBNP value below 500 pg/ml, whereas it was the case in 8 (30.8%) non-ARF controls and in 12 (20.7%) noncardiac ARF patients. Conclusions In cancer patients with ARF, plasma NT-proBNP concentration is not a relevant tool to recognize cardiac dysfunction, but is specific enough to rule out the diagnosis in patients with plasma NT-proBNP concentrations below 500 pg/ml.