Concordance Between Hemoglobin and Hematocrit Among Children and Pregnant Persons in National Health and Nutrition Examination Survey Data, 1999-2020

Maren E Wolf; Maria Elena D Jefferds; Lisa D Gardner; Zuguo Mei; Christine M Pfeiffer; O Yaw Addo

doi:10.1016/j.tjnut.2024.12.029

Concordance Between Hemoglobin and Hematocrit Among Children and Pregnant Persons in National Health and Nutrition Examination Survey Data, 1999-2020

J Nutr. 2024 Dec 30:S0022-3166(24)01256-2. doi: 10.1016/j.tjnut.2024.12.029. Online ahead of print.

Authors

Maren E Wolf¹, Maria Elena D Jefferds², Lisa D Gardner², Zuguo Mei², Christine M Pfeiffer³, O Yaw Addo⁴

Affiliations

¹ Epidemic Intelligence Service, Centers for Disease Control and Prevention, Atlanta, GA; International Micronutrient Malnutrition Prevention and Control (IMMPaCt) Program, Nutrition Branch, Division of Nutrition, Physical Activity, and Obesity, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA.
² International Micronutrient Malnutrition Prevention and Control (IMMPaCt) Program, Nutrition Branch, Division of Nutrition, Physical Activity, and Obesity, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA.
³ Nutritional Biomarkers Branch, Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA.
⁴ International Micronutrient Malnutrition Prevention and Control (IMMPaCt) Program, Nutrition Branch, Division of Nutrition, Physical Activity, and Obesity, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA. Electronic address: lyu6@cdc.gov.

PMID: 39742969
DOI: 10.1016/j.tjnut.2024.12.029

Abstract

Background: Hemoglobin and hematocrit are the two most common biomarkers used to identify anemia in clinical settings, but their results do not always agree.

Objective: To examine agreement between hemoglobin and hematocrit in identifying anemia among children aged 1-<5 years and pregnant persons.

Methods: Pregnant persons and children aged 1-<5 years with hemoglobin and hematocrit results from the same whole blood sample in National Health and Nutrition Examination Survey (NHANES,1999-2020) were included. We used the Centers for Disease Control and Prevention (CDC) anemia cutoff values for children, pregnancy status, trimester, and smoking adjustments. We examined concordance of anemia, sensitivity, and specificity among those with anemia based on at least one test overall and by race/ethnicity, sex, and income level. Cohen's kappa was used to measure concordance.

Results: Analytic samples included 7,052 children and 1,437 pregnant persons, of which 1,119 had trimester data. Among children, anemia prevalence was 3.7% (95% CI: 3.1-4.3) based on hemoglobin and 5.5% (95% CI: 4.7-6.3) based on hematocrit. Among pregnant persons, anemia prevalence based on hemoglobin was 7.7% (95% CI: 5.9-9.5) and 12.4% (95% CI: 10.1-14.6) based on hematocrit. Kappa scores overall and by sociodemographic characteristics ranged from 0.64-0.75 (moderate concordance) among children and 0.53-0.78 (weak to moderate concordance) among pregnant persons. Among those with anemia on at least one test, 53.5% of children and 61.5% of pregnant persons had anemia based on both tests.

Conclusions: We found substantial discordance between the two biomarkers; about 50% of children and 40% of pregnant women were identified by only one of the two biomarkers. Because hemoglobin and hematocrit may be used interchangeably in the clinical setting, individuals with anemia may be missed, not receive treatment, and therefore be at higher risk of adverse pregnancy, birth, and developmental outcomes.

Keywords: NHANES; anemia; children; concordance; discordance; hematocrit; hemoglobin; pregnant.