title: The effects of storage time and sampling season on the stability of serum 25-hydroxy vitamin D and androstenedione.
abstract: Knowledge of the stability of serum samples stored in large biobanks is pivotal for reliable assessment of hormone-dependent disease risks. We studied the effects of sample storage time and season of serum sampling on the stability of 25-hydroxy vitamin D (25-OHD) and androstenedione in a stratified random sample of 402 women, using paired sera from the Finnish Maternity Cohort. Serum samples selected were donated between 6 and 24 yr ago. The storage time did not affect serum 25-OHD and androstenedione levels. However, there was a significant mean difference in the 25-OHD levels of sera withdrawn during winter (first sample) vs. during summer (second sample; -18.4 nmol/l, P <or= 0.001). Also at the individual level, there were significant differences in average 25-OHD levels between individuals with the paired sera taken at winter-winter compared with other alternatives (summer-winter, winter-summer, and summer-summer). The androstenedione levels showed no such differences. Long-term storage does not affect serum 25-OHD and androstenedione levels, but sampling season is an important determinant of 25-OHD levels. Stored serum samples can be used to study disease associations with both hormones. However, sampling season needs to be taken into account for 25-OHD by considering matching and stratification and, if possible, serial sampling.
authors.affiliation: University of Tampere, Tampere, Finland. calypse.agborsangaya@uta.fi
authors.forename: Calypse
authors.initials: C
authors.lastname: Agborsangaya
authors.forename: Adetunji T
authors.initials: AT
authors.lastname: Toriola
authors.forename: Kjell
authors.initials: K
authors.lastname: Grankvist
authors.forename: Heljia-Marja
authors.initials: HM
authors.lastname: Surcel
authors.forename: Katsiaryna
authors.initials: K
authors.lastname: Holl
authors.forename: Seppo
authors.initials: S
authors.lastname: Parkkila
authors.forename: Pentti
authors.initials: P
authors.lastname: Tuohimaa
authors.forename: Annekatrin
authors.initials: A
authors.lastname: Lukanova
authors.forename: Matti
authors.initials: M
authors.lastname: Lehtinen
mesh_terms: D000328:Adult; D000735:Androstenedione / Q000097:blood*; D001800:Blood Specimen Collection / Q000379:methods; D004355:Drug Stability; D005260:Female; D005387:Finland; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D012621:Seasons; D013997:Time Factors; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; D000735:Androstenedione; C104450:25-hydroxyvitamin D