Diagnostic significance of NT-proBNP estimation in patients with acute dyspnea.

OBJECTIVE: To determine the diagnostic significance of plasma NT-proBNP estimation in patients presenting with acute dyspnea in Emergency Department.

STUDY DESIGN: An observational, cross sectional study.

PLACE AND DURATION OF STUDY: From January to June 2008 at Liaquat National Hospital, Karachi.

METHODOLOGY: In this study, 100 patients were selected with purposive non-probability sampling who had presented to the emergency department with acute dyspnea. Plasma NT-proBNP levels, chest X-ray and transthoracic echocardiography were performed at the time of admission. NT-proBNP levels were assessed by commercial tests. The clinical diagnosis of congestive heart failure, patient's hospital course and discharge diagnosis were cross-tabulated with NT-proBNP levels. The chi-square test for categorical data and Student's t-test for numerical data was applied at 0.05 level of significance to compare patients with and without heart failure (HF). Further comparative analysis between age groups was done by one way ANOVA test.

RESULTS: The mean NT-proBNP level among the 79 subjects with a final diagnosis of heart failure was 10918 compared with 461 pg/ml in those without heart failure (p=0.001). The diagnostic accuracy of NT-proBNP at a cutoff of 300 pg/milliliter (ml) was 100 percent. An optimal strategy to identify acute HF was to use age-related cut-points of 450 and 900 pg/ml for ages < 50 and > 50 years, which yielded 100% sensitivity and 86% specificity for acute HF. An age-independent cut-point of 300 pg/ml had 100% negative predictive value to exclude acute HF.

CONCLUSION: NT-proBNP is useful in establishing or excluding the diagnosis of congestive heart failure in patients with acute dyspnea.