Iron Deficiency Prevalence Differs According to Definition Used for Women

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A higher serum ferritin threshold could lead to better diagnosis and treatment of more women with iron deficiency.

Multiple definitions of iron deficiency were associated with significantly different prevalences among women, notwithstanding self-reported age, pregnancy, or race and ethnicity, according to a recent cross-sectional study.

The three iron deficiency definitions used in the analysis consisted of a combined transferring saturation <10% and serum ferritin <15 ng/mL (Hemochromatosis and Iron Overload Screening Study [HEIRS]), serum ferritin <15 ng/mL (World Health Organization [WHO]), and serum ferritin <25 ng/mL (a threshold for iron-deficient erythropoiesis [IDE]).

“Using higher serum ferritin thresholds to define iron deficiency could lead to diagnosis and treatment of more women with iron deficiency and greater reduction of related morbidity,” wrote the investigative team, led by James C. Barton, MD, Southern Iron Disorders Center.

Impacting more than 2 million worldwide, young women and children are especially affected by iron deficiency. For women, iron deficiency increases the risk of fatigue, impaired muscular performance, cold intolerance, and adverse pregnancy outcomes.

The laboratory definition of iron deficiency typically consists of low serum iron, low transferrin saturation, and low serum ferritin — population studies tend to define iron deficiency by serum ferritin alone. In the current analysis, Barton and colleagues used the three definitions to compare the prevalence of iron deficiency in the HEIRS cohort of women.

HEIRS evaluated the prevalence, genetic and environmental determinants, and the clinical, personal, and societal outcomes of hemochromatosis, iron overload, and iron-related disorders in a sample of 101,168 adults enrolled from 2001 to 2003 at 5 field centers in the United States and Canada.

The sample comprised volunteer women aged ≥25 years recruited at primary care centers associated with the field centers. All women who had not heard of the HEIRS study, reported previous hemochromatosis and iron overload diagnosis, or met pertinent study criteria were included for analysis.

Among 62,685 women (mean age, 49.58 years), 1957 (3.12%) had iron deficiency according to the HEIRS definition, 4659 (7.43%) according to the WHO definition, and 9611 (15.33%) according to the IDE definition. Among 40,381 women aged 25 to 52, the prevalence rates of iron deficiency, according to these definitions, were 4.46%, 10.57%, and 21.23%, respectively.

Among those aged 25 to 44 years, who reported pregnancy, the prevalence rates of iron deficiency were 5.44% (n = 111), 18.05% (n = 368), and 36.10% (n = 736) according to the HEIRS, WHO, and IDE definitions, respectively.

Across racial and ethnic groups, the prevalence of iron deficiency increased significantly according to the definition used, from 3.12% for HEIRS, 7.43% for WHO, and 15.33% for IDE. These rates were notably higher among Black and Hispanic women than Asian and White women.

Overall, the relative iron deficiency prevalence among these women increased 2.4-fold (95% CI, 2.3 - 2.5; P <.001) using the WHO definition and increased 4.9-fold (95% CI, 4.7 - 5.2; P <.001) based on the IDE definition.

In a linked editorial, Michelle Sholzberg, MDCM, MSc, St Michael’s Hospital, University of Toronto, explained these data emphasized the importance of applying evidence-based definitions and screening for iron deficiency, particularly for women of color.

“It bears repeating: nonanemic iron deficiency and iron deficiency anemia are associated with morbidity and mortality,” Sholzberg wrote. “Nonanemic iron deficiency, iron deficiency anemia, and their consequences are preventable, but screening practices and guidelines are inconsistent.”

Sholzberg described how a woman with iron deficiency should not be considered normal in practice, pointing to the lack of screening programs for female individuals of reproductive age. Individuals of low socioeconomic status are at high risk of iron deficiency but are less likely to experience screening and treatment.

“Thus, the most vulnerable are also the least likely to be tested and treated, which further exacerbates the oppressive cycle imposed by a discriminatory structure,” Sholzberg added. “To facilitate better care, we must dismantle structural racism and sexism that is inappropriately normalizing nonanemic iron deficiency and iron deficiency anemia in women.”