A prospective study in search of an optimal B-natriuretic peptide level to screen patients for cardiac dysfunction

Background Although echocardiography is the gold standard test for suspected left ventricular dysfunction, its cost and availability limits its use as a routine screening tool. The high negative predictive value of B-natriuretic peptide (BNP) in dyspneic patients suggests its possible utility in screening patients prior to echocardiography. Determining an appropriate BNP level below which the need for echocardiography is precluded would be valuable. We hypothesized that a fixed plasma BNP level of 20 pg/mL and simple clinical parameters are an effective pre-echocardiographic screening tool for left ventricular dysfunction. Methods Two hundred and two patients at a Veterans Administration facility with symptoms suggestive of heart disease (male to female ratio 193:9, mean age 65 years) were screened prior to echocardiography. Patients with known cardiac dysfunction were excluded. Results BNP levels of ≥20 pg/mL were 79% sensitive and 44% specific in screening for any abnormality of ventricular function. The negative predictive value was 69%. When broken down into categories of dysfunction, the cutoff point of 20 pg/mL had a better negative predictive value for those with systolic dysfunction (96%) or systolic plus diastolic dysfunction (100%) if patients with diastolic dysfunction were excluded. The majority of patients with falsely low BNP levels (<20 pg/mL with positive echocardiographic findings) had mild diastolic dysfunction, with 3 patients exhibiting mild systolic dysfunction. Conclusions BNP may be a useful screening tool for left ventricular dysfunction in patients with history suggestive of heart disease and be used to assist in forming a pretest probability, which in turn could greatly assist in appropriateness of patient referral and in optimization of drug therapy.