HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) 078451.Supplemental Data All Versions of this Article: clinchem.2006.078451v1 53/4/781    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Fazili, Z. Articles by Zhang, M. Search for Related Content PubMed PubMed Citation Articles by Fazili, Z. Articles by Zhang, M. Related Collections Nutrition

Comparison of Serum Folate Species Analyzed by LC-MS/MS with Total Folate Measured by Microbiologic Assay and Bio-Rad Radioassay

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 Highway, NE, Mail Stop F55, Atlanta, GA 30345; fax 770-488-4139, e-mail CPfeiffer{at}cdc.gov

Abstract

Background: The Bio-Rad QuantaPhase II radioassay (BR), used for 25 years to measure total folate (TFOL) concentrations for the National Health and Nutrition Examination Survey (NHANES), will be discontinued in 2007. Liquid chromatography–tandem mass spectrometry (LC-MS/MS) or a microbiologic assay (MA) will be used in the future.

Methods: We measured folate species by LC-MS/MS and TFOL by MA and BR in 327 serum samples.

Results: LC-MS/MS measured 5-methyltetrahydrofolic acid (5CH₃THF; 82%), folic acid (FA; 8%), 5-formyltetrahydrofolic acid (5CHOTHF; 6%), tetrahydrofolic acid (THF; 4%), and 5,10-methenyltetrahydrofolic acid (5,10CH=THF; 0%). The sum of the folate species correlated well with TFOL measured by MA (R² = 0.97) and BR (R² = 0.91). Compared with LC-MS/MS results, MA and BR values were significantly lower (–6% and –29%, respectively); however, these differences were concentration dependent. The MA almost completely recovered folates added to serum samples except for FA [69% (3%)] and THF [36% (10%)]. The BR underrecovered 5CH₃THF [61% (9%)] and 5CHOTHF [38% (14%)] and overrecovered 5,10CH=THF [234% (32%)]. Multiple linear regression models with log-transformed data yielded a good fit for converting BR data to MA or LC-MS/MS data and MA data to LC-MS/MS data.

Conclusions: The good correspondence between the sum of folate species determined by LC-MS/MS and TFOL determined by MA makes these 2 assays interchangeable. The BR produces much lower results, on average, probably because of 5CH₃THF underrecovery. The conversion equations provided could be used for future NHANES time trend analyses.

The following articles in journals at HighWire Press have cited this article:

				R. Hannisdal, P. M. Ueland, and A. Svardal Liquid Chromatography-Tandem Mass Spectrometry Analysis of Folate and Folate Catabolites in Human Serum Clin. Chem., June 1, 2009; 55(6): 1147 - 1154. [Abstract] [Full Text] [PDF]

				L. A Houghton, J. Yang, and D. L O'Connor Unmetabolized folic acid and total folate concentrations in breast milk are unaffected by low-dose folate supplements Am. J. Clinical Nutrition, January 1, 2009; 89(1): 216 - 220. [Abstract] [Full Text] [PDF]

				Z. Fazili, C. M. Pfeiffer, M. Zhang, R. B. Jain, and D. Koontz Influence of 5,10-Methylenetetrahydrofolate Reductase Polymorphism on Whole-Blood Folate Concentrations Measured by LC-MS/MS, Microbiologic Assay, and Bio-Rad Radioassay Clin. Chem., January 1, 2008; 54(1): 197 - 201. [Abstract] [Full Text] [PDF]