Clinical utility of pleural N-terminal-proB-type natriuretic peptide (NTproBNP) to distinguish heart failure related pleural effusions from effusions of other causes

<bold>Introduction:</bold> Current biochemical criteria for pleural fluid (PF) analysis, such as Light’s criteria (LC), can falsely diagnose heart failure related pleural effusions (HFPE) as exudates. The utility of pleural fluid (PF) NTproBNP to diagnose HFPE was compared to current biochemical criteria. <bold>Methods:</bold> This was a single-centre prospective study. PF was prospectively collected from patients with pleural effusion, measured for NTproBNP, and compared with LC and serum-PF protein gradient (SPPG). Patients with HFPE met clinical, biochemical and echocardiographic criteria for heart failure. Echocardiogram was performed in patients with raised serum NTproBNP. <bold>Results:</bold> 81 patients (49 male, 60.5%) of mean age 67.4±13.4 years were analysed. 26 had HFPE (32.1%) and 55 had pleural effusions of other causes(67.9%). Median serum and PF NTproBNP levels were 8833(IQR 2965-21577)pg/mL and 12084(IQR 3528-23818)pg/mL in patients with HFPE, and 179(IQR 90-359.5)pg/mL and 208(IQR 97.9-463.3)pg/mL in those with other pleural effusions. Sensitivity of PF NTproBNP ≥1200pg/mL, LC and SPPG ≥31g/L to detect HFPE was 88.4%(95%CI 68.7-97%), 53.8%(95%CI 33.7-72.9%), and 80.7%(95%CI 60-92.7%), and specificity was 94.5% (95%CI 83.9-98.6%), 87.2%(95%CI 74.9-94.3%), and 76.3%(95%CI 62.7-86.3%) respectively. PF NTproBNP (cut-off ≥1200pg/mL) had an area under receiver operating characteristic curve of 0.915(95%CI 0.835-0.995), compared to 0.706(95%CI 0.575-0.836) for LC and 0.786(95%CI 0.676-0.895) for SPPG. <bold>Conclusion:</bold> PF NTproBNP (cut-off: ≥1200pg/mL) has higher sensitivity and specificity than other biochemical criteria in identifying HFPE in Asian patients.