Abstract
Abstract Background B-type natriuretic peptide (BNP) and its precursor N-terminal pro-B-type natriuretic peptide (NT-proBNP) are released primarily by the ventricles in the heart in response to volume or pressure overload. Measurements of NT-proBNP are used as an aid in the diagnosis and assessment of severity of congestive heart failure (CHF). Within- (CVI) and between-subject (CVG) biological variation (BV) estimates for NT-proBNP are limited. Here biological variability (BV) estimates from eight apparently healthy Turkish women for NT-proBNP are provided. Methods Serum samples were collected weekly from 24 healthy subjects (12 male, 12 female) for 10 consecutive weeks and stored at −80 °C prior to analysis. Study participant samples were analyzed in duplicate within a single run using the Atellica® IM NT-proBNP (PBNP) assay* on the Atellica IM Analyzer. Outlier detection, variance homogeneity analyses, and trend analysis were performed followed by CV-ANOVA to determine BV and analytical variation (CVA) estimates with 95% CI. The asymmetrical reference change values (RCV) using the lognormal approach, index of individuality (II), and analytical performance specification (APS), based on the CVA estimate derived in our study, were also calculated. Results PBNP results from 11 males and 3 females were lower than the limit of quantitation (LoQ) of the assay (<35 pg/mL). The remaining male sample was not included in the analysis. One female sample was identified as an outlier between individuals and was excluded from the analysis. To fulfil criteria for variance homogeneity of the data from eight women, 7% of results were excluded. In total, 104 analytical results were included in the analysis. PBNP data for the female group was normally distributed, and no trends were identified by regression analysis. The BV estimates derived from females were CVI: 23.7%, (95% CI 19.0–30.4) and CVG: 8.22%, (95% CI 0.0–24.7). The CVA obtained from replicate test results was 11.2% (95% CI 9.4–13.9), which was lower than the desirable APS for imprecision. The II, calculated as the ratio of CVI/CVG, indicated a low individuality of PBNP (defined as II > 1.6). Thus, use of a population-based reference interval for interpreting serial PBNP measurements is more appropriate than use of the RCV. Conclusions This study provides updated BV estimates for NT-proBNP derived from a protocol consistent with European Federation of Clinical Chemistry and Laboratory Medicine recommendations. The availability of BV estimates allows for refined APS and associated II and RCV, which are applicable when using PBNP as an aid in the diagnosis and assessment of severity of congestive heart failure. *The products/features mentioned here are not commercially available in all countries. Their future availability cannot be guaranteed.
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