Comparison between analytical performances of polyclonal and monoclonal electrochemiluminescence immunoassays for NT-proBNP.

Background: We evaluated the analytical characteristics of electrochemiluminescence (ECLIA) immunoassay for NT-proBNP (proBNP II, Roche Diagnostics, Germany) and compared its analytical performance to that of the previous polyclonal method.

Methods: We measured NT-proBNP in EDTA plasma samples of 177 consecutive cardiac patients (69 females and 108 males; mean age 62.2+/-16.4 years, range 13 to 96 years) with monoclonal and polyclonal ECLIA methods following manufacturer's instructions using an Elecsys 2010 analyzer.

Results: Monoclonal ECLIA method for NT-proBNP assay showed an imprecision (CV%) lower than 3% at the cut-off value (i.e., 150 ng/L). No significant interference was found in plasma samples containing high levels of hemoglobin, triglycerides or bilirubin. EDTA plasma showed slightly, but significantly lower NT-proBNP values than serum (on average -6.3%) and lithium-heparinized plasma (on average -3.9%) samples. Finally, a very close linear regression was found between the NT-proBNP values found by either monoclonal or polyclonal ECLIA method (monoclonal ECLIA=-72.17+1.04 polyclonal ECLIA, n=177, R=0.993).

Conclusions: The monoclonal ECLIA method showed very similar analytical characteristics with slightly lower NT-proBNP results (on average -2.5%) than the polyclonal ECLIA method. The difference between monoclonal and polyclonal methods seems to be too slight to change the reference range and decisional values for NT-proBNP assay, as previously assessed by the polyclonal ECLIA method.