Serum ferritin, soluble transferrin receptor, and total body iron for the detection of iron deficiency in early pregnancy: a multiethnic population-based study with low use of iron supplements

Abstract

Which blood-based indicator best reflects the iron status in pregnant women is unclear. Better assessments of iron status in today's multiethnic populations are needed to optimize treatment and clinical recommendations. We aimed to determine the prevalence of anemia (hemoglobin <11.0g/dL in first and <10.5g/dL in second trimester) and iron deficiency (ID) by the iron indicators serum ferritin <15µg/L, serum soluble transferrin receptor (sTfR) >4.4mg/L, and calculated total body iron <0mg/kg, and their associations with ethnicity. This was a population-based cross-sectional study from primary antenatal care of 792 healthy women in early pregnancy in Oslo, Norway. We categorized the women into 6 ethnic groups: Western European, South Asian, Middle Eastern, Sub-Saharan African, East Asian, and Eastern European. Anemia was found in 5.9% of women (Western Europeans: 1.8%; non-Western: 0-14%, P<0.05). ID from ferritin was found in 33% (Western Europeans: 15%; non-Western: 27-55%, P<0.05). ID from sTfR was found in 6.5% (Western Europeans: 0.3%; non-Western: 0-20%, P<0.01). Calculated total body iron indicated ID in 11% (Western Europeans: 0.6%, non-Western: 7.0-28%, P<0.01). The prevalence of ID was significantly higher by all measures in South Asian, Sub-Saharan African, and Middle Eastern than in Western European women, and the ethnic differences persisted after adjusting for confounders. South Asians, Sub-Saharan Africans, and Middle Easterners had lower iron concentrations by all measures for all hemoglobin intervals. Anemia related to ID varied from 35% (sTfR) to 46% (total body iron) and 72% (ferritin) depending on the iron indicator used. Women at the highest risk of ID and anemia were of South Asian, Middle Eastern, and Sub-Saharan African origin. The prevalence of ID differed considerably depending on the iron indicator used.