Effect of renal failure on N-terminal Pro-Brain natriuretic peptide in patients admitted to emergency department with acute dyspnea

OBJECTIVE: Preexisting renal failure diminishes the excretion of N-Terminal Pro-Brain Natriuretic Peptide (NT-proBNP), therefore limits the diagnostic value of this peptide for concomitant heart failure. The aim of this study was to evaluate the association between NT-proBNP and the stages of renal dysfunction in a typical population attended to emergency department with acute dyspnea. METHODS: In this cross-sectional study, all consecutive patients with acute dyspnea underwent clinical evaluation, laboratory assessment of NT-proBNP, and echocardiographic examinations. Among subjects, 54.5% were diagnosed as heart failure. Grouping variables according to renal function capacity and ejection fraction, independent variables were compared with Kruskal-Wallis or ANOVA with posthoc tests. Correlation and linear regression analysis were done to analyze the variables associated with NT-proBNP. The diagnostic performance of NT-proBNP was evaluated by receiver-operating characteristic (ROC) curve. RESULTS: Serum median NT-proBNP level in patients with severe renal impairment was significantly higher than moderate and mildly decreased renal functions (p=0.001). In patients with moderate and severe left ventricular failure, NT-proBNP was significantly higher compared with normal subjects (LVEF>50%) (p=0.040, and 0.017, respectively). Renal dysfunction was associated in 56% of patients with heart failure. The area under the ROC curve of NT-proBNP for identifying left ventricular failure in patients with renal failure (eGFR<90 mL/min/1.73 m2) was 0.649 and reached significant difference (95% CI:0.548-0.749, p=0.005). CONCLUSION: In addition to NT-proBNP measurement in clinical judgement of heart failure, renal functions have to be taken into consideration to avoid misdiagnosis.