Assessment of the Myocardial Stress Biomarker NT-proBNP in Real Clinical Practice

Abstract

The objective. To compare the clinical informativeness of NT-proBNP plasma concentrations measured using a domestic enzyme-linked immunoassay (ELISA) kit or commonly employed in clinical practice direct immunochemiluminescence assay (ICLA).Subjects and Methods. The study involved 35 vascular surgery patients of varying degrees of cardiological risk. Blood specimens were collected from each patient at 3 time-points: 1. prior to surgery (NT-proBNP₁), 2 — after the procedure (NT-proBNP₂), 3 — before the discharge from the hospital (NT-proBNP₃). Each specimen was split into equal aliquots for biomarker quantification using two different techniques (ELISA using domestic reagents — for the 1st series of analyses, and ICLA using an imported kit — for the 2nd series). Perioperative cardiovascular complications were recorded. The consistency of the measurement results obtained by two different methods was evaluated using the Bland–Altman technique. A discrimination ability of independent variables in relation to a binary dependent variable was studied using ROC analysis.Results. In the 1st series, ranges of the biomarker were as follows: NT-proBNP₁ — 24–774 pg/ml, NT-proBNP₂ — 41.2–889.1 pg/ml, NT-proBNP₃ — 39.3–1013.3 pg/ml. In the 2nd series, NT-proBNP₁ was 31.2–2087.0 pg/ml, NT-proBNP₂ — 32.5–3754.0 pg/ml, NT-proBNP₃ — 34.1–2728.0 pg/ml. In the Bland–Altman analysis, 97.03% of the values fell within the lower and upper limits of consistency (±1.96 SD of the average difference), which indicated comparability of the results in the series, but the values of NT-proBNP in the 1st series were lower than in the 2nd ones. Cardiovascular complications were registered in 3 (8.5%) patients. In the 1st series, NT-proBNP₁ > 218 pg/ml predicted cardiovascular complications with a sensitivity of 66.7% and a specificity of 81.3% (AUC 0.844, 95% CI 0.681–0.944, P = 0.0003). In the 2nd series, NT-proBNP₁ > 315 pg/ml predicted cardiovascular complications with a sensitivity of 66.7% and a specificity of 75.0% (AUC 0.828, 95% CI 0.663–0.934, P = 0.001).Conclusion. The domestic ELISA kit for solid-phase enzyme immunoassay proved its clinical informativeness for quantitation of NT-proBNP demonstrating its value for diagnostic and prognostic purposes, or scientific studies. The novel domestic technique provides consistently reproducible results, although with lower reference values as compared to the standard immunochemiluminescence assay