Red Cell Folate Testing
Unwarranted and Overutilized in the Era of Folic Acid Supplementation
Folate
November 2010
Folate is a water-soluble B vitamin that is essential for adequate health. Folate, along with vitamin B12, is essential for DNA synthesis, repair, and methylation. Folate coenzymes are also integral in reactions involving one-carbon metabolism, and although there are various forms of methylated folate in the body, the primary form is 5-methyltetrahydrofolate. 5-methylTHF is also a cosubstrate required by methionine synthase for the conversion and demethylation of homocysteine to methionine. Therefore, in the setting of folate deficiency there will be an accumulation of homocysteine. Folate and vitamin B12 (or cobalamin) metabolism are linked by the reaction that transfers a methyl group from 5-methyltetrahydrofolate to B12. Homocysteine, along with methylmalonic acid, will also be elevated in the setting of B12 deficiency, and a combination of MMA and homocysteine has been proposed by some to distinguish between B12 and folate deficiency.
Folate |
Jump to section:
- Introduction
- Folate
- Folate
- Selected Food Sources of Folate and Folic Acid*
- Causes of Folate Deficiency
- Laboratory Diagnosis of Folate Deficiency
- Folate and Vitamin B12 Deficiency
- Quantitation of Folate: Methods
- Differences Between Folate Immunoassays
- Analytical Imprecision: RBC Folate (CAP Surveys)
- Equivalence of Serum and RBC Folate
- Modern Folate Deficiency is Rare
- Mayo RBC/Serum Folate Orders 1999-2009
- Conclusions
- Questions?
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