title: Stability of blood (pro)vitamins during four years of storage at -20 degrees C: consequences for epidemiologic research.
abstract: We studied the effects of frozen storage on (pro)vitamin concentrations in EDTA-plasma and whole blood. Aliquots from 55 samples were analyzed before storage and after 3, 6, 12, 24, 36 and 48 months at -20 degrees C. Dramatic decreases occurred for EDTA-plasma concentrations of vitamin E between 6 and 12 months, vitamin A, total carotenoids and beta-carotene after 1 year, and whole blood niacin. A smaller decrease was observed for folic acid at 1 year of storage, but the level remained constant thereafter. The vitamins D, B6, B12 (EDTA-plasma), B1 and B2 (whole blood) showed no decline during 4 years of storage. With the exception of folic acid, the observed decreases varied considerably among subjects. Therefore using EDTA-plasma stored longer than 1 year at -20 degrees C will result in highly attenuated odds ratios when assessing the relationship between vitamin A, carotenoids, or vitamin E with a given disease. Attenuation will also occur when using niacin concentrations in whole blood stored for 4 years at -20 degrees C.
authors.affiliation: Department of Chronic Disease and Environmental Epidemiology, National Institute of Public Health and Environmental Protection, Bilthoven, The Netherlands.
authors.forename: M C
authors.initials: MC
authors.lastname: Ockè
authors.forename: J
authors.initials: J
authors.lastname: Schrijver
authors.forename: G L
authors.initials: GL
authors.lastname: Obermann-de Boer
authors.forename: B P
authors.initials: BP
authors.lastname: Bloemberg
authors.forename: G R
authors.initials: GR
authors.lastname: Haenen
authors.forename: D
authors.initials: D
authors.lastname: Kromhout
mesh_terms: D000328:Adult; D000368:Aged; D001793:Blood Preservation; D016022:Case-Control Studies; D016001:Confidence Intervals; D015925:Cryopreservation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D013997:Time Factors; D014815:Vitamins / Q000097:blood*
chemical_list: D014815:Vitamins