Plasma Brain Natriuretic Peptide Measured by Fully-Automated Immunoassay and by Immunoradiometric Assay Compared

The clinical relevance of measuring plasma brain natriuretic peptide (BNP) is well-known, especially in patients with heart failure. Recently, a new method for measuring BNP, called TRIAGE, has been developed which can be used for point-of-care testing of patients with congestive heart failure. The aim of the present study is to compare the analytical performance of this fully-automated method to that of an immunoradiometric assay (IRMA), routinely used to measure BNP. The TRIAGE method is a non-competitive immunofluorometric assay which uses two different binding phases, specific for two different epitopes of the BNP amino acid chain, to form a sandwich with the specific ligand (i.e., BNP). A polyclonal antibody is included in the fluorescent immunoassay reagents which are contained in the assay devices and a monoclonal antibody is immobilized in the detection lane of the assay device. The imprecision of the TRIAGE method was approximately 12% for BNP concentrations in the normal range and about 18% for BNP concentrations above the normal range. The mean reading time of the TRIAGE method was 14.5 +/- 8.6 min. A close linear relationship was found between the BNP values measured with the two methods (TRIAGE = 24.6+0.933 IRMA; r = 0.932, n = 83). The TRIAGE method is indicated for BNP assay in ambulatory and coronary or emergency units, where usually only a few samples (preferentially whole blood samples) must be measured in a short time. The IRMA method should be preferred for pathophysiological studies, requiring the highest degree of precision and sensitivity for simultaneous measurement of several stored plasma samples or tissue extracts.