(P29-015-23) Adjusting Iron Status for Inflammation in Non-Pregnant Women of Reproductive Age in the United States (NHANES 2009-2010; 2015-2020)

Objectives: As biomarkers commonly used to measure iron status (serum ferritin (SF) and soluble transferrin receptor (sTfR)) are affected by inflammation, we examined the impact of adjusting for inflammation on the prevalence of iron deficiency (ID) in non-pregnant women in the United States.

Methods: Using data from the nationally representative National Health and Nutrition Examination Survey (NHANES) 2009-2010, 2015-2016, and 2017-2020, we compared unadjusted and inflammation-adjusted prevalence estimates of ID in non-pregnant women of reproductive age (WRA; 15 to 49 years). We examined two cut-offs to define ID using SF: 1) <15 µg/L (based on the World Health Organization’s (WHO) 2020 recommendations), and 2) < 25 µg/L (based on a physiologically-based threshold reflecting iron-deficient erythropoiesis). The cut-off to define ID using total body iron (a ratio of sTfR to SF) was ≤0 mg/kg. Iron status was adjusted for C-reactive protein (CRP), a measure of acute inflammation, using the regression approach developed by the Biomarkers Reflecting Inflammation and Nutrition Determinants of Anemia (BRINDA) project.

Results: In NHANES 2009-2010, 2015-2020, the prevalence of acute inflammation as measured by CRP >5 mg/L was 17.9% (95% confidence interval (CI) 16.5, 19.4) in WRA. The prevalence of ID in WRA varied depending on the biomarker and cut-offs used. Adjusting for inflammation significantly increased the prevalence of ID for both cut-offs of SF. In WRA overall, adjusting for inflammation increased the prevalence of low SF >15 µg/L from 15.5% (95% CI 14.1, 17.0) to 20.6% (95% CI 19.0, 22.1), low SF < 25 µg/L from 28.8% (95% CI 27.2, 30.5) to 37.7% (95% CI 35.9, 39.6), and low total body iron from 9.5% (95% CI 8.3, 10.8) to 11.9% (95% CI 10.6, 13.3).

Conclusions: The prevalence of ID as measured by low SF and low TBI may be underestimated if not adjusted for inflammation in WRA. Based on the WHO’s guidelines for ferritin, adjusting the WHO-recommended ferritin cut-off for inflammation moved the prevalence of ID from a mild to a moderate public health problem among WRA in the United States, while the prevalence of ID after adjusting the physiologically-based cut-off for inflammation almost reached the level of a high public health problem (≥40%).

Funding Sources: No funding was used for this analysis.