title: Assessing the influence of 5,10-methylenetetrahydrofolate reductase polymorphism on folate stability during long-term frozen storage, thawing, and repeated freeze/thawing of whole blood.
abstract: BACKGROUND
  Limited information is available on folate stability, particularly vitamer stability by 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T genotype, during frozen storage, thawing, and repeated freeze/thawing (F/T) of whole blood (WB).
  
  
  METHODS
  We assessed folate stability after storing undiluted WB for up to 30 mo at -70°C and measuring folate vitamers by LC-MS/MS at 6, 14, 20 and 30 mo in samples with C/C and T/T genotype (n=13 each). We investigated folate stability during 3-h thawing of WB (n=2 each/genotype) and during repeated F/T of WB (n=4 each/genotype).
  
  
  RESULTS
  We found significant decreases in total folate (TFOL) (median decrease: 8.8% for C/C and 16% for T/T), methyl folate (7.9% for C/C and 10% for T/T), and non-methyl folate (19% for C/C and 24% for T/T) concentrations from 6 to 30 mo WB frozen storage. During thawing of WB at room temperature and repeated F/T, samples with T/T genotype were susceptible to greater folate losses than samples with C/C genotype.
  
  
  CONCLUSIONS
  Long-term frozen storage of WB resulted in significant folate losses of ~10-25% that are clinically unacceptable. Frozen WB should not be exposed to more than 1h of thawing time and repeated F/T of WB should be avoided.
authors.affiliation: Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341, United States.
authors.forename: Zia
authors.initials: Z
authors.lastname: Fazili
authors.forename: Maya R
authors.initials: MR
authors.lastname: Sternberg
authors.forename: Christine M
authors.initials: CM
authors.lastname: Pfeiffer
mesh_terms: D001793:Blood Preservation / Q000379:methods*; D005492:Folic Acid / Q000097:blood*; D005615:Freezing; D005838:Genotype; D006801:Humans; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000097:blood / Q000235:genetics*; D011110:Polymorphism, Genetic; D013763:Tetrahydrofolates / Q000097:blood
chemical_list: D013763:Tetrahydrofolates; D005492:Folic Acid; D042965:Methylenetetrahydrofolate Reductase (NADPH2); C005984:5-methyltetrahydrofolate