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Applying inappropriate cutpoints leads to misinterpretation of folate status in the U.S. population1–5
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12 2016
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Source: Am J Clin Nutr. 104(6):1607-1615
[PDF-116.24 KB]
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Alternative Title:Am J Clin Nutr
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Description:Background
Folate cutpoints for risk of deficiency vs. possible deficiency were originally derived differently (experimental vs. epidemiologic data) and their interpretation is different. Matching cutpoints derived from one assay with population-based data derived from another assay requires caution.
Objective
We assessed the extent of folate status misinterpretation using inappropriate cutpoints.
Methods
In the cross-sectional NHANES, serum and red blood cell (RBC) folate were first measured using a radioproteinbindingassay (RPBA, 1988–2006), then using a microbiologic assay (MBA, 2007–2010). We compared prevalence estimates for assay-matched (e.g., using RPBA cutpoint with RPBA data) and assay-mismatched (e.g., using MBA cutpoint with RPBA data) cutpoints for risk of deficiency based on megaloblastic anemia as a hematologic indicator in persons ≥4 y [e.g., <7 nmol/L serum folate, <305 nmol/L RBC folate, derived by MBA], possible deficiency based on rising homocysteine as a metabolic indicator in persons ≥4 y (e.g., <10 nmol/L serum folate, <340 nmol/L RBC folate, derived by RPBA), and insufficiency based on elevated risk of neural tube defects in women 12–49 y (e.g., <906 nmol/L RBC folate, derived by MBA).
Results
Pre-folic acid fortification (1988–1994), risk of deficiency for assay-matched vs. assay-mismatched cutpoints was 5.6% vs. 16% (serum folate) and 7.4% vs. 28% (RBC folate); it declined post-fortification (1999–2006) to <1% vs. <1% (serum folate) and <1% vs. 2.5% (RBC folate). Pre-fortification (1988–1994), risk of possible deficiency for assay-matched vs. assay-mismatched cutpoints was 35% vs. 56% (serum folate) and 37% vs. 84% (RBC folate); it declined post-fortification (1999–2006) to 1.9% vs. 7.0% (serum folate) and 4.8% vs. 53% (RBC folate). Post-fortification (2007–2010), risk of insufficiency was 23% (assay-matched) vs. 39% (assay-mismatched).
Conclusions
Applying assay-mismatched cutpoints leads to misinterpretation of folate status. This likely applies to clinical assays as no comparability data are available.
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Pubmed ID:27680995
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Pubmed Central ID:PMC5693380
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