Background: Plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) levels are elevated in patients with secondary pulmonary hypertension and chronic lung disease with right ventricular overload. The aim of the present study was to investigate the use of plasma NT-proBNP levels as a prognostic marker of severe COPD with chronic respiratory failure and latent pulmonary hypertension.
Methods: Plasma NT-proBNP levels were measured in 61 patients with stable COPD. Plasma NT-proBNP levels, pulmonary function, PaO(2), and PaCO(2) levels and systolic pulmonary artery pressure were compared according to COPD severity. In addition, we examined correlations between plasma NT-proBNP levels and pulmonary function, PaO(2), PaCO(2), and systolic pulmonary artery pressure.
Results: The levels of plasma NT-proBNP significantly increased in patients with stage IV and stage III COPD compared to individuals with stage II COPD according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification. The area under the receiver-operating characteristic curve of plasma NT-proBNP for severe to very severe COPD (FEV(1) <50%) was 0.707 (95% confidence interval [CI] 0.566-0.847, P=0.008). Plasma NT-proBNP levels significantly correlated with %FEV(1) (r= -0.557; P < 0.001), arterial blood gas parameters such as PaCO(2) (r = 0.476; P < 0.001) and PaO(2) (r = -0.347; P = 0.031), and systolic pulmonary artery pressure (r = 0.435; P = 0.001).
Conclusions: Plasma NT-proBNP levels increased significantly with disease severity, progression of chronic respiratory failure, and secondary pulmonary hypertension in patients with stable COPD. These results suggest that plasma NT-proBNP can be a useful prognostic marker to monitor COPD progression and identify cases of secondary pulmonary hypertension in patients with stable COPD.