Biological variation of holotranscobalamin and cobalamin in healthy individuals

Abstract

Data on biological variation for cobalamin and holotranscobalamin (holoTC) are limited. The aim of this study was to determine within-subject (CVI) and between-subject (CVG) biological variations for these analytes in a healthy population. We collected blood samples from 15 healthy volunteers (12 women and three men, 22–66 years) on the same weekday for 10 consecutive weeks. Serum samples were stored at –80 °C until analysis in duplicate in a single analytical run. The CVI and CVG were estimated by nested ANOVA. The CVI (95% CI) for cobalamin and holoTC was 6.7% (5.7–7.7) and 13.0% (11.5–15.0), respectively. The corresponding CVG was 24.1% (16.4–36.0) and 24.6% (16.3–37.7). The analytical variation (CVA) (95% CI) was 3.5% (3.2–4.0) for cobalamin and 2.4% (2.1–2.6) for holoTC. The index of individuality (II) was low (<0.6) for both cobalamin and holoTC and the reference change value (RCV) was 20.1% for cobalamin and 36.6% for holoTC. Our study describes the components of biological variation of cobalamin and holoTC in a healthy population, contributing to a better clinical interpretation of these biomarkers.