Biological variation estimates for serum N-terminal pro-B-type natriuretic peptide from 8 healthy Turkish female individuals

N-terminal pro-B-type natriuretic peptide (NT-proBNP) measurements are widely used for diagnosing and assessing the severity of congestive heart failure (CHF). However, limited information is available about the within (CVI) and between-subjects (CVG) biological variation (BV). This study presents BV estimates for NT-proBNP in eight healthy Turkish women. Serum samples were collected weekly from 24 healthy subjects over 10 weeks and analyzed using the Siemens ADVIA Centaur (R) XP NT-proBNP assay. Outlier detection, variance homogeneity and trend analysis were performed followed by CV-ANOVA for BV and analytical variation coefficient (CVA) estimation. The reference change values (RCV), the index of individuality (II), and the analytical performance specification (APS), were also calculated. NT-proBNP results from 11 males and three females were below the assay's limit of quantitation (LoQ). One female was identified as outlier between individuals. To fulfil criteria for variance homogeneity of the data from eight women, 7% of results were excluded. Ultimately, 104 analytical results from eight females were included in the analysis. NT-proBNP data for the female group were normally distributed and no trends were identified by regression analysis. The BV estimates were CVI: 23.7% [95% confidence interval (CI): 19.0-30.4%] and CVG: 8.22% (95% CI: 0.0-24.7%). The CVA obtained from samples replicate results was 11.2% (95% CI: 9.4-13.9%), lower than the desirable APS for imprecision. The II indicated a low individuality of NT-proBNP. This study provides BV estimates for NT-proBNP derived from a protocol consistent with European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) recommendations. BV data on NT-proBNP represent an update of the presently available data, some of them obtained more than 20 years ago.