Diagnostic accuracy of B type natriuretic peptide and amino terminal proBNP in the emergency diagnosis of heart failure

Abstract

Objective: To compare head to head the diagnostic accuracy of B type natriuretic peptide (BNP) and the amino terminal fragment of its precursor hormone (NT-proBNP) for congestive heart failure (CHF) in an emergency setting.

Methods: 251 consecutive patients presenting to the emergency department with dyspnoea as a chief complaint were prospectively studied. Patients with acute coronary syndromes were excluded. The diagnosis of CHF was based on the Framingham score for CHF plus echocardiographic evidence of systolic or diastolic dysfunction. Blood concentrations of BNP and NT-proBNP were measured by two commercially available assays (Abbott and Roche methods). The diagnostic accuracies of BNP and NT-proBNP were assessed by receiver operating characteristic curve analysis.

Results: Areas under the curve for BNP and NT-proBNP in patients with dyspnoea caused by CHF (n = 137) and in patients with dyspnoea attributable to other reasons (n = 114) did not differ significantly (area under the curve 0.916 v 0.903, p = 0.277, statistical power 94%). Cut off concentrations with the highest diagnostic accuracy were 295 ng/l for BNP (sensitivity 80%, specificity 86%, diagnostic accuracy 83%) and 825 ng/l for NT-proBNP (sensitivity 87%, specificity 81%, diagnostic accuracy 84%). Evaluation of discordant false classifications at these cut off concentrations showed no advantage for either BNP nor NT-proBNP in the biochemical diagnosis of CHF (17 misclassifications by BNP and 14 by NT-proBNP, p = 0.720). In the population studied, age, sex, and renal function had no impact on the diagnostic utility of both tests when compared by logistic regression models.

Conclusions: BNP and NT-proBNP may be equally useful as an aid in the diagnosis of CHF in short of breath patients presenting to the emergency department.

Figures

Figure 1

Trial profile. ACS, acute coronary syndromes; AF, atrial fibrillation; BNP, B-type natriuretic peptide; CHF, congestive heart failure; NSTEMI, non-ST elevation myocardial infarction; NT-proBNP, amino terminal fragment of proBNP; STEMI, ST elevation myocardial infarction.

Figure 2

Box and whisker plots of BNP and NT-proBNP for patients with dyspnoea caused by CHF (n  =  137) and for patients with dyspnoea attributable to non-cardiac causes (n  =  114). In the box and whisker plots, the central box spans from the lower to the upper quartile, the middle line is the median, the whiskers extend from the minimum to the maximum concentration, excluding outside and far out concentrations, which are displayed as separate points. Grey boxes, box and whisker plots for BNP; white boxes, box and whisker plots for NT-proBNP.

Figure 3

Receiver operating characteristic (ROC) plot for BNP and NT-proBNP comparing patients with dyspnoea caused by CHF (n  =  137) versus patients with dyspnoea attributable to other reasons (n  =  114). The area under the curve for BNP is 0.916 and for NT-proBNP is 0.903 (difference of 0.013 not significant, p  =  0.277). Solid line, ROC curve for BNP; dashed line, ROC curve for NT-proBNP.

Figure 4

Scatter plot for BNP versus NT-proBNP. Spearman’s coefficient of rank correlation (n  =  239): 0.914 (95% CI 0.890 to 0.932, p