Population RBC folate concentrations can be accurately estimated from measured whole blood folate, measured hemoglobin, and predicted serum folate—cross-sectional data from the NHANES 1988–2010
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Population RBC folate concentrations can be accurately estimated from measured whole blood folate, measured hemoglobin, and predicted serum folate—cross-sectional data from the NHANES 1988–2010

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  • English
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    Details:

    • Alternative Title:
      Am J Clin Nutr
    • Personal Author:
    • Description:
      Background:

      RBC folate (RBF) is an indicator of folate status and risk of neural-tube defects. It is calculated from whole blood folate (WBF), serum folate (SFOL), and hematocrit (Hct). SFOL and/or Hct are sometimes unavailable; hemoglobin (Hb) is generally available in surveys.

      Objectives:

      We assessed the ability of different RBF approximations to generate population data in women aged 12–49 y.

      Methods:

      Using SFOL, RBF, Hct, Hb, and mean corpuscular Hb content (MCHC) from prefortification (1988–1994) and postfortification (1999–2006, 2007–2010) NHANES we applied 6 approaches: #1) assume SFOL = 0; #2) impute SFOL (population median); #3) impute Hct (population median); #4) estimate Hct (Hb/MCHC); #5) assume SFOL = 0 and estimate Hct; and #6) predict SFOL (from WBF) and estimate Hct. For each approach, we calculated the paired percentage difference to the “true” RBF and estimated various statistics.

      Results:

      For 2007–2010 (unweighted data), the median relative difference from “true” RBF was lowest for approaches #2 (−0.74%), #4 (−0.96%), and #6 (−1.15%), intermediate for #3 (−3.36%), and highest for #5 (4.96%) and #1 (5.78%). The 95% agreement limits were smallest for approach #1 (2.33%, 13.0%) and largest for #3 (−20.8%, 11.3%). Approach #2 showed concentration-dependence (negative compared with positive differences at low compared with high RBF). Using weighted data, we found similar patterns across approaches for mean relative differences by demographic subgroup for all 3 time periods.

      Conclusions:

      We obtained the best agreement between estimated and “true” RBF when we predicted SFOL using a regression equation obtained from a subset of samples (approach #6). Alternatively, the consistent overestimation of RBF when assuming SFOL = 0 (~6%) could be addressed by adjusting the data (approach #5). Similar observations for pre- and postfortification periods suggest applicability to low and high folate status situations, but should be confirmed elsewhere. To estimate RBF, at least WBF and Hb are needed. Am J Clin Nutr 2020;111:601–612.

    • Subjects:
    • Source:
      Am J Clin Nutr. 111(3):601-612
    • Pubmed ID:
      31858145
    • Pubmed Central ID:
      PMC10059072
    • Document Type:
      Journal Article
    • Funding:
      CC999999/ImCDC/Intramural CDC HHSUnited States/
    • Name as Subject:
      National Health and Nutrition Examination Survey (U.S.)
    • Place as Subject:
      United States
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