Hemoglobin and red cell indices correlated with serum ferritin concentration in late pregnancy

Objective: To study the correlation between third-trimester serum ferritin concentration and hemoglobin and red cell indices to select the best hematologic characteristic to identify women who need iron therapy. Methods: In a prospective study, blood was drawn from pregnant women with hemoglobin above 10 g/dL, and thalassemia trait excluded at booking, at 28–30 weeks’ gestation to study the correlation (Spearman ρ value) between serum ferritin concentration and hemoglobin level, mean corpuscular volume, mean cell hemoglobin, mean cell hemoglobin concentration, and hematocrit. The best relationship was identified using receiver operating characteristic (ROC) curves. Results: Serum ferritin concentration correlated significantly with hemoglobin (ρ = .211), mean corpuscular volume (ρ = .332), mean cell hemoglobin (ρ = .304), and hematocrit (ρ = .199). The area under the ROC curve was largest for hemoglobin. Conclusion: Serum ferritin concentration at the early third trimester correlated best with hemoglobin level. If a hemoglobin level of 11 g/dL or below (25% of all patients) was used as the cutoff, 64% of women who needed iron therapy were identified.