Abstract
BackgroundRecent studies have shown that in addition to brain (or B-type) natriuretic peptide (BNP) and the N-terminal proBNP fragment, levels of intact proBNP are also increased in heart failure. Moreover, present BNP immunoassays also measure proBNP, as the anti-BNP antibody cross-reacts with proBNP. It is important to know the exact levels of proBNP in heart failure, because elevation of the low-activity proBNP may be associated with the development of heart failure.Methodology/Principal FindingsWe therefore established a two-step immunochemiluminescent assay for total BNP (BNP+proBNP) and proBNP using monoclonal antibodies and glycosylated proBNP as a standard. The assay enables measurement of plasma total BNP and proBNP within only 7 h, without prior extraction of the plasma. The detection limit was 0.4 pmol/L for a 50-µl plasma sample. Within-run CVs ranged from 5.2%–8.0% in proBNP assay and from 7.0%–8.4% in total BNP assay, and between-run CVs ranged from 5.3–7.4% in proBNP assay and from 2.9%–9.5% in total BNP assay, respectively. The dilution curves for plasma samples showed good linearity (correlation coefficients = 0.998–1.00), and analytical recovery was 90–101%. The mean total BNP and proBNP in plasma from 116 healthy subjects were 1.4±1.2 pM and 1.0±0.7 pM, respectively, and were 80±129 pM and 42±70 pM in 32 heart failure patients. Plasma proBNP levels significantly correlate with age in normal subjects.Conclusions/SignificanceOur immunochemiluminescent assay is sufficiently rapid and precise for routine determination of total BNP and proBNP in human plasma.
Highlights
Brain natriuretic peptide (BNP) has been used as a biomarker of heart failure for more than a decade [1]
We investigated the effects of dilution on plasma levels of total BNP and proBNP in three heart failure patients
When we assessed the intra- and inter-assay precision using plasma spiked with glycosylated proBNP or BNP, we found that the intra-assay CV ranged from 5.2%–8.0% in proBNP assay and from 7.0%–8.4% in total BNP assay, while inter-assay CV ranged from 5.3–7.4% in proBNP assay and from 1.9%–9.5% in total BNP assay, respectively (Table 3, 4)
Summary
Brain ( known as B-type) natriuretic peptide (BNP) has been used as a biomarker of heart failure for more than a decade [1]. Recent studies have shown that in addition to BNP and the NT-proBNP, levels of uncleaved proBNP are considerably increased in plasma of patients with heart failure [5,6,7]. This is noteworthy in part because the immunoassay system currently being used to measure BNP levels detects proBNP, as the anti-BNP antibody cross-reacts with proBNP. Recent studies have shown that in addition to brain (or B-type) natriuretic peptide (BNP) and the N-terminal proBNP fragment, levels of intact proBNP are increased in heart failure. It is important to know the exact levels of proBNP in heart failure, because elevation of the low-activity proBNP may be associated with the development of heart failure
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