Reticulocyte Hemoglobin Use for Prediction of Iron Deficiency Anemia in Pregnancy.

OBJECTIVE: The objective of this study is to determine the optimal first trimester reticulocyte hemoglobin cutoff to predict iron deficiency anemia at 24 to 28 weeks' gestation and to compare its performance to first trimester ferritin. STUDY DESIGN: This prospective, observational cohort study enrolled pregnant patients in the first trimester (last menstrual period to 136/7 weeks) at NYU Langone Health between February 2022 and June 2022. Eligible participants were nonanemic (hemoglobin ≥ 11.0 g/dL), ages 18 to 65, with singleton gestation enrolled before 140/7 weeks. Patients with first trimester anemia or blood transfusion 3 months prior to pregnancy were excluded. Iron deficiency anemia was defined as hemoglobin < 10.5 g/dL and ferritin < 30 µg/L. Optimal cutoffs were calculated using the receiver operating characteristic curve and the sensitivity/specificity pairs with the largest Youden index. RESULTS: Of 600 nonanemic, pregnant participants enrolled, 499 participants were eligible for analysis at 24 to 28 weeks' gestation; 40 (8%) had iron deficiency anemia. The area under the curve of reticulocyte hemoglobin was 0.69 (95% confidence interval [CI]: 0.61-0.78) compared with 0.73 (95% CI: 0.65-0.81) for ferritin. The optimal first trimester cutoff was 32.6 pg for reticulocyte hemoglobin (sensitivity 42.5%, specificity 86.9%) and 29 µg/L for ferritin (sensitivity 47.5, specificity 87.6%). CONCLUSION: First trimester reticulocyte hemoglobin did not outperform ferritin in predicting iron deficiency anemia at 24 to 28 weeks' gestation. Both reticulocyte hemoglobin and ferritin were weak predictors of iron deficiency anemia at 24 to 28 weeks and were more effective in identifying patients at low risk of iron deficiency anemia at 24 to 28 weeks.