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Comparison of serum and red blood cell folate microbiologic assays for national population surveys.

Authors :
Pfeiffer CM
Zhang M
Lacher DA
Molloy AM
Tamura T
Yetley EA
Picciano MF
Johnson CL
Source :
The Journal of nutrition [J Nutr] 2011 Jul; Vol. 141 (7), pp. 1402-9. Date of Electronic Publication: 2011 May 25.
Publication Year :
2011

Abstract

Three laboratories participated with their laboratory-specific microbiologic growth assays (MA) in the NHANES 2007-2008 to assess whether the distributions of serum (n = 2645) and RBC folate (n = 2613) for the same one-third sample of participants were comparable among laboratories. Laboratory (L) 2 produced the highest and L1 the lowest serum and RBC folate geometric means (nmol/L) in the NHANES sample (serum: L1, 39.5; L2, 59.2; L3, 47.7; and RBC: L1, 1120; L2, 1380; L3, 1380). Each laboratory produced different reference intervals for the central 95% of the population. Pearson correlation coefficients were highest between L3 and L1 (serum, r = 0.95; RBC, r = 0.92) and lowest between L2 and L1 (serum, r = 0.81; RBC, r = 0.65). Notable procedural differences among the laboratories were the Lactobacillus rhamnosus microorganism (L1 and L3: chloramphenicol resistant, L2: wild type) and the calibrator [L1: [6S]5-methyltetrahydrofolate (5-methylTHF), L2: [6R,S] 5-formyltetrahydrofolate ([6R,S] 5-formylTHF), L3: folic acid (FA)]. Compared with 5-methylTHF as calibrator, the folate results were 22-32% higher with FA as calibrator and 8% higher with 5-formylTHF as calibrator, regardless of the matrix (n = 30 serum, n = 28 RBC). The use of different calibrators explained most of the differences in results between L3 and L1 but not between L2 and L1. The use of the wild-type L. rhamnosus by L2 appeared to be the main reason for the differences in results between L2 and the other 2 laboratories. These findings indicate how assay variations influence MA folate results and how those variations can affect population data. To ensure data comparability, better assay harmonization is needed.

Details

Language :
English
ISSN :
1541-6100
Volume :
141
Issue :
7
Database :
MEDLINE
Journal :
The Journal of nutrition
Publication Type :
Academic Journal
Accession number :
21613453
Full Text :
https://doi.org/10.3945/jn.111.141515