Analytical performance and clinical results of a fully automated MEIA system for brain natriuretic peptide assay: comparison with a point of care testing method

Abstract

AbstractThe aim of this study was to evaluate the analytical performance of a recently available immunoassay for brain natriuretic peptide (BNP), based on microparticle enzyme immunoassay (MEIA, AxSYM System, Abbott Laboratories), whose analytical characteristics and clinical results were compared with those of a point of care testing (POCT) method (TRIAGE system, Biosite Diagnostics). The within-run and total imprecision of the MEIA system were 18.4% and 19.8% at 21 ng/l, 8.0% and 14.8% at 183 ng/l, and 5.7% and 14.0% at 319 ng/l, respectively. The detection limit of the MEIA system was tested by repeatedly measuring (n = 20) the 0 calibrator in four different runs; a mean +3 SD value of 5.6 ± 4.8 ng/l (range 1.8–12.6 ng/l) was obtained. A close linear relationship (MEIA = –22.5 + 1.71 POCT method, R = 0.950, n = 296) was found (BNP concentration: 5–5500 ng/l), with a significant bias (mean difference: 164.8 ng/l, p < 0.0001). Mean BNP concentration measured in 94 reference subjects (57 women and 37 men; mean age 43.5 ± 14.0 years) was higher with MEIA than POCT, (25.9 ± 32.7 ng/l vs. 11.7 ± 8.9 ng/l, p < 0.0001). The same trend was observed also in 202 cardiac patients (620.6 ± 1082.2 ng/l vs. 386.1 ± 594.5 ng/l, p < 0.0001). Our data suggest that MEIA and POCT have quite similar analytical performance but different clinical results. Then, different reference values, as well as cut-off values, should be taken into account for the clinical use of these two immunoassays.