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.

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.