Role of the plasma brain natriuretic peptide in differentiating patients with congestive heart failure from other diseases

Background: Heart failure (HF) is primarily a disease of the elderly. The incidence of congestive heart failure (CHF) in Thailand has been increasing during the last 10 years. Unlike other diseases, physicians have only rough patients' symptoms and physical findings to guide the adequacy of treatment. Recently, there has been evidence of the role of brain natriuretic peptide (BNP) and its use in HF concerning diagnosis, prognosis, and treatment follow-up. The purpose of this study was to determine the sensitivity and specificity of N-terminal part of brain natriuretic peptide plasma level (NT-proBNP) in the diagnosis of HF in Thai patients who presented with dyspnea. Method: The design was a cross sectional study. The authors enrolled 50 consecutive patients from the Respiratory Unit with dyspnea from chronic obstructive pulmonary disease (COPD), asthma, or anxiety. The cardiovascular cause of dyspnea such as pulmonary emboli and poor left ventricular ejection fraction (LVEF) were excluded. Forty eight consecutive patients with evidence of HF who presented to the Cardiac Center with a history of dyspnea on exertion were assigned as cases. Five milliliters of venous blood samples were taken and sent together with 200 samples from a normal healthy population from the check up department for NT-proBNP measurement. Results: In case and control groups, there were no statistical significances in sex (males 68.8% vs females 52.0%, p > 0.05) and age (63.3 + 14.9 vs 55.6 + 16.9; p > 0.05). The mean left ventricular ejection fraction in the case group was 32.4 + 9.7 per cent. There was significant difference between value of NT-proBNP in the control group (386 + 1,041 pg/ml) and in the case group (8,912 + 12,525 pg/ml, p < 0.001). To diagnose HF in patients who presented with dyspnea using the cut-off value of NT-proBNP at > 150 pg/ml in patients with dyspnea the sensitivity was 96 per cent, and the specificity of 72 per cent; at > 200 pg/ml the sensitivity was 96 per cent and the specificity was 80 per cent and at > 300 pg/ml the sensitivity was 94 per cent and specificity of 82 per cent. Plasma level of NT-proBNP increased significantly with increasing New York Heart Association (NYHA) functional class (class II: 1,107 + 1,091 pg/ml; class III: 5,097 + 4,201 pg/ml, class IV: 19,389 + 15,966 pg/ml p < 0.01). There was no significant difference of plasma NT-proBNP levels in patients with ischemic (8,586 + 11,601 pg/ml; n = 35) and those with non ischemic cardiomyopathy (9,789 + 15,229 pg/ml; n = 13). Plasma NT-proBNP was associated with neck vein distension (p < 0.05) but there was no significant association with S3, paroxysmal nocturnal dyspnea, rales, cardiomegaly, acute pulmonary edema, serum sodium (r = 0.22), ejection fraction (r = -0.18) and subsequent hospital death (p > 0.05). Conclusion: Measurement of plasma NT-proBNP proved to be a useful diagnostic test in differentiating HF from other causes in patients who presented with dyspnea.