Influence of 5,10-methylenetetrahydrofolate reductase polymorphism on whole-blood folate concentrations measured by LC-MS/MS, microbiologic assay, and bio-rad radioassay.
BACKGROUND
The 5,10-methylenetetrahydrofolate reductase (NADPH) (MTHFR) C677T polymorphism may affect whole-blood folate pattern measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and total folate measured by LC-MS/MS, microbiologic assay, and Bio-Rad radioassay (BR).


METHODS
We analyzed 171 whole blood hemolysates from 2 blood banks for folate pattern and total folate concentrations using these 3 methods and determined MTHFR genotype.


RESULTS
The median (range) total folate concentration by LC-MS/MS was higher in the US set [378 (228-820) nmol/L; n = 96] than in the European set [250 (122-582) nmol/L; n = 75]. The whole-blood folate pattern [median (range)] was similar for individuals with C/C (n = 73) and C/T (n = 66) genotype: 88% (71%-91%) and 86% (50%-91%), respectively, for 5-methyltetrahydrofolic acid (5CH(3)THF) vs 12% (9%-29%) and 14% (9%-51%) for forms other than 5-methyltetrahydrofolic acid (non-5CH(3)THF). Individuals with T/T (n = 32) genotype had 58% (22%-87%) 5CH(3)THF vs 42% (13%-78%) non-5CH(3)THF. Compared with microbiologic assay results, LC-MS/MS (r = 0.94) and BR (r = 0.87) results were significantly lower (-10% and -45%, respectively); however, these differences were concentration dependent and also genotype dependent for the BR assay (-48% for C/C+C/T and -31% for T/T). The microbiologic assay completely recovered [mean (SD)] folates added to a whole blood hemolysate, except for tetrahydrofolic acid (THF) [46.4% (8.1%)]. The BR assay under-recovered 5CH(3)THF [51% (4.1%)] and 5-formyltetrahydrofolic acid [18% (0.1%)], and over-recovered THF [152% (19%)].


CONCLUSIONS
MTHFR C677T polymorphism influences the folate pattern in whole blood. The agreement between total folate by LC-MS/MS and microbiologic assay, independent of the MTHFR genotype, allows the use of one regression equation. Because BR results are genotype dependent, different regression equations should be used.
Fazili
Zia
Z
Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, 4770 Buford Highway NE, Atlanta, GA 30345, USA.
Pfeiffer
Christine M
CM
Zhang
Mindy
M
Jain
Ram B
RB
Koontz
Deborah
D
D001771:Blood Banks; D002853:Chromatography, Liquid; D005492:Folic Acid / Q000097:blood*; D006801:Humans; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000235:genetics*; D008828:Microbiological Techniques; D011110:Polymorphism, Genetic; D011869:Radioligand Assay; D012044:Regression Analysis; D053719:Tandem Mass Spectrometry
D005492:Folic Acid; D042965:Methylenetetrahydrofolate Reductase (NADPH2)