Congestive heart failure (CHF) is a major public health problem and is a common diagnosis in patients who are older than 65 years. The incidence is expected to continue to rise as the population ages. Diagnosing CHF is challenging because the symptoms are vague and other comorbidities can mimic them. However, brain natriuretic peptide (BNP) tests have shown promising accuracy in the diagnosis of CHF.
Currently, the enzyme-linked immunosorbent assay (ELISA) method and the radio-immunosorbent assay (RIA) are used to measure BNP. The ELISA test has an advantage because it is performed at a patient’s bedside and can provide the physician with a quick CHF diagnosis; however, the accuracy of the tests is uncertain.
The authors searched multiple databases to systematically review the literature on the evidence and accuracy of the ELISA and RIA methods. In addition, they contacted leading experts and the manufacturers of the BNP tests. Studies included in the review compared BNP assay in patients who were asymptomatic or in patients who had acute CHF with echocardiography or radionuclide scans. Data from the studies were pooled and analyzed.
Nineteen studies with 22 patient populations and 9,093 participants were included in the analysis. Five studies examined the ELISA assay, one study evaluated the ELISAN-terminal pro-BNP (NT-pro-BNP) test, and 13 involved the RIA method. The populations of the studies were heterogeneous, and physicians referred 10 to 31 percent of outpatients with heart failure. The specificity of the two tests was 72 percent, the sensitivity was 87 percent, and the combined negative likelihood ratio was 0.18 (0.12 for the ELISA assay; 0.23 for the RIA). If the pretest probability of CHF was 20 percent, the authors found that a negative result of the ELISA test had a posttest probability of 2.9 percent compared with 5.4 percent for the RIA test.
The authors conclude that BNP tests could be used in a low-risk population to reduce the need for echocardiography and referrals to other subspecialists. The ELISA test has an advantage over the RIA test, but the authors stress that it also has a higher cost.