The clinical value of rapid assay for plasma B-type natriuretic peptide in differentiating congestive heart failure from pulmonary causes of dyspnoea

BACKGROUND: B-type natriuretic peptide (BNP) is a cardiac neurohormone secreted from the cardiac ventricles in response to pressure overload. OBJECTIVE: To evaluate the optimal cutoff point of plasma BNP in diagnosing congestive heart failure (CHF). METHODS: We conducted a prospective study of 195 patients who were hospitalised with dyspnoea. Pulmonary capillary wedge pressure (PCWP) was measured with a Swan-Ganz catheterisation and plasma BNP level was obtained by a rapid immunofluorescence assay in all patients. PCWP >12 mmHg was chosen as the golden standard for left ventricular dysfunction in this study. The subjects were divided into two groups by the criteria, one group with dyspnoea caused by CHF (n=134) and the other caused by lung diseases (n=61). RESULTS: (1) BNP cutoff point of 100 pg/ml had a sensitivity of 94.34%, a specificity of 92.13% and an accuracy of 93.33% for differentiating CHF from pulmonary dyspnoea. (2) By multiple logistic-regression analysis, measurements of BNP added significantly independent predictive power to other clinical variables in models predicting which patients had CHF. CONCLUSION: A value of 100 pg/ml or more for a rapid BNP assay may be the most accurate independent predictor of the presence or absence of CHF.