Overview of the in vitro stability of commonly measured vitamins and carotenoids in whole blood
Résumé
Background The pre-analytical stabilities of vitamins A, E, K, B1, B2, B6, B12, C, carotenoids and folates in whole blood were studied. The aim of this work was to provide clear and workable pre-analytical procedures specifying optimal delay before freezing for laboratories which perform themselves such analyses or which receive and transfer such specimens to referral laboratories.Methods The stability of vitamins was studied in whole blood at room temperature after light exposure up to 24h (vitamin C), 48h (vitamins A, E, B1, B2, B6 and carotenoids) and 72h (vitamins K, B12, red blood cell (RBC) and serum folates). Vitamin C stability after baseline acidification was analysed up to 48h. Changes observed were compared to a clinical cut-off defined as total change limit based on a combination of analytical performance and within-subject variation.Results Clinically and statistically significant changes occurred only in vitamins C (-22.5%), B6 (+9.9%) and serum folates (-16.8%) concentrations after 6, 24 and 48h, respectively. Vitamins A, E, K, B1, B2, B12, RBC folates and carotenoids showed good stability up to 48 or 72h. Vitamin C in acidified serum conserved at room temperature appeared unstable. The optimal condition for acidified vitamin C conservation was at less than -20?.Conclusion The majority of vitamins remain stable for up to 48h. Vitamin C quantification requires serum acidification followed by freezing as soon as possible. Freezing, respectively, within 12h and 24h for determination of plasma vitamin B6 and serum folates concentrations is recommended.
