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Clinical Chemistry 54: 197-201, 2008; 10.1373/clinchem.2007.096545
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(Clinical Chemistry. 2008;54:197-201.)
© 2008 American Association for Clinical Chemistry, Inc.

Brief Communications

Influence of 5,10-Methylenetetrahydrofolate Reductase Polymorphism on Whole-Blood Folate Concentrations Measured by LC-MS/MS, Microbiologic Assay, and Bio-Rad Radioassay

Zia Fazili, Christine M. Pfeiffera, Mindy Zhang, Ram B. Jain and Deborah Koontz

Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia;

aaddress correspondence to this author at: Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, 4770 Buford Hwy, NE, Mail Stop F55, Atlanta, GA 30345. e-mail CPfeiffer{at}cdc.gov.


Abstract

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 (5CH3THF) vs 12% (9%–29%) and 14% (9%–51%) for forms other than 5-methyltetrahydrofolic acid (non-5CH3THF). Individuals with T/T (n = 32) genotype had 58% (22%–87%) 5CH3THF vs 42% (13%–78%) non-5CH3THF. 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 underrecovered 5CH3THF [51% (4.1%)] and 5-formyltetrahydrofolic acid [18% (0.1%)], and overrecovered THF [152% (19%)].

Conclusion: 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.






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