Distribution of 25-hydroxyvitamin D3 in dried blood spots and implications for its quantitation by tandem mass spectrometry

Abstract Dried blood spots (DBS) are a convenient collection and archiving method for blood specimens. The interest in screening certain analytes in neonatal DBS continues to increase for a variety of paediatric disorders. 25-Hydroxyvitamin D 3 (25OHD 3 ) is one such analyte. We investigated potential factors that may affect the analysis of 25OHD 3 in prospective cohorts of DBS, such as blood spot volume, hole punch position, and paper type. All of these factors were shown to affect 25OHD 3 levels measured. When blood volumes of 3 concentrations extracted were significantly lower ( P 3 concentrations significantly higher in outer punched spots compared to those punched from the centre ( P P ® and FTA ® ), and paper type was shown to be highly relevant. We also show that the distribution of 25OHD 3 in whole blood is essentially extracellular, with over 98% of 25OHD 3 residing in the serum component. This may potentially explain why the diffusion properties of blood and type of chromatographic paper may significantly influence the distribution of such analytes in DBS. These factors should be taken into consideration for the prospective collection of DBS and analysis of 25OHD 3 in DBS.