Renal function, congestive heart failure, and amino-terminal pro-brain natriuretic peptide measurement - Results from the ProBNP Investigation of Dyspnea in the Emergency Department (PRIDE) study

OBJECTIVES We sought to examine the interaction between renal function and amino-terminal pro-brain natriuretic peptide (NT-proBNP) levels. BACKGROUND The effects of renal insufficiency on NT-proBNP among patients with and without acute congestive heart failure (CHF) are controversial. We examined the effects of kidney disease on NT-proBNP-based CHF diagnosis and prognosis. METHODS A total of 599 dyspneic patients with glomerular filtration rates (GFRs) as low as 14.8 ml/min were analyzed. We used multivariate logistic regression to examine covariates associated with NT-proBNP results and linear regression analysis to analyze associations between NT-proBNP and GFR. Receiver-operating characteristic analysis determined the sensitivity and specificity of NT-proBNP for CHF diagnosis. We also assessed 60-day mortality rates as a function of NT-proBNP concentration. RESULTS Glomerular filtration rates ranged from 15 ml/min/1.73m(2) to 252 ml/min/1.73m(2). Renal insufficiency was associated with risk factors for CHF, and patients with renal insufficiency were more likely to have CHF (all p < 0.003). Worse renal function was accompanied by cardiac structural and functional abnormalities on echocardiography. We found that NT-proBNP and GFR were inversely and independently related (p < 0.001) and that NT-proBNP values of >450 pg/ml for patients ages <50 years and >900 pg/ml for patients >= 50 years had a sensitivity of 85% and a specificity of 88% for diagnosing acute CHF among subjects with GFR >= 60 ml/min/1.73m(2). Using a cut point of 1,200 pg/ml for subjects with GFR <60 ml/min/1.73m(2), we found sensitivity and specificity, to be 89% and 72%, respectively. We found that NT-proBNP was the strongest overall independent risk factor for 60-day mortality (hazard ratio 1.57; 95% confidence interval 1.2 to 2.0; p = 0.0004) and remained so even in those with GFR <60 ml/min/1.73 m 2 (hazard ratio 1.61; 95% confidence interval 1.14 to 2.26; p = 0.006). CONCLUSIONS The use of NT-proBNP testing is valuable for the evaluation of the dyspneic patient with suspected CHF, irrespective of renal function.