Serum B-type natriuretic peptide is more accurate than ascites analyses in the diagnosis of ascites related to heart failure

Abstract

Purpose: Heart failure (HF) is, after cirrhosis, the second most common cause of ascites. Serum B-type natriuretic peptide (BNP) plays an important role in the diagnosis of HF. We therefore hypothesized that BNP would be useful in the differential diagnosis of ascites. Methods: Consecutive patients with new onset ascites were prospectively enrolled in this cross-sectional study. All patients had measurements of serum-ascites albumin gradient (SAAG), total protein concentration in ascitic fluid, serum and ascites BNP. We enrolled 218 consecutive patients with ascites due to HF (n=44), cirrhosis (n=162), peritoneal disease (n=10) and constrictive pericarditis (n=2). Results: Compared to SAAG and/or total protein concentration in ascitic fluid, the test that best discriminated HF-related ascites from other causes of ascites was serum BNP. A cutoff of >364 pg/mL (sensitivity 98%, specificity 99%, diagnostic accuracy 99%) had the highest positive likelihood ratio (168.1), that is, it was the best to rule-in HF-related ascites. Conversely, a cutoff ≤182 pg/mL had the lowest negative likelihood ratio (0.0) and was the best to rule-out HF-related ascites. These findings were confirmed in a 60-patient validation cohort. Conclusions: Serum BNP is more accurate than ascites analyses in the diagnosis of HF-related ascites. The workup of patients with new onset ascites could be streamlined by obtaining serum BNP as an initial test. A positive test would forego the need for a diagnostic paracentesis.