(807) Utility of reticulocyte hemoglobin equivalent in screening for iron deficiency in pregnancy

Objective: Reticulocyte hemoglobin equivalent (Ret-He) is the measure of functional iron available in hemoglobin of reticulocytes and may be an early indicator of iron deficiency (ID) prior to other red blood cell parameters. It has gained popularity in screening for ID in non-pregnant populations due to its convenience of testing, rapidity of results and cost-effectiveness. Unlike ferritin, Ret-He is not an acute phase reactant and not affected by inflammation. The objective of this study was to determine the accuracy of Ret-He in detecting ID in pregnancy compared to ferritin.

Study Design: This was a prospective cohort study which included 200 pregnant patients. Participants were recruited in any trimester if a complete blood count (CBC) was drawn as part of routine prenatal care. For those who agreed to participate, Ret-He and ferritin were collected simultaneously with the CBC. Exclusion criteria included age < 18 , multifetal gestations, thalassemia or sickle cell disease and chronic kidney or liver disease. Ferritin level below 30 ng/mL was considered the gold standard for diagnosing ID. Spearman correlation was conducted to test the association between Ret-He and ferritin. Sensitivity and specificity were calculated for different Ret-He cutoff points. Receiver Operating Curve (ROC) analysis with area under the curve (AUC) was performed to assess the value of Ret-He in identifying ID.

Results: Of 200 pregnant women recruited, 52, 72 and 76 were enrolled in the first, second and third trimesters, respectively. There was a weak but statistically significant correlation between ferritin and Ret-He (r_s=0.48, p< .0001). A Ret-He cutoff of 30.3, the lower threshold used by our laboratory for non-pregnant individuals, had a sensitivity of 30% and specificity of 90%. Alternatively, a Ret-He cutoff point of 34.0 had a sensitivity of 72% and specificity of 54%. The AUC for Ret-He was 0.65, predicting poor discrimination between patients with and without ID.

Conclusion: Ret-He is a poor predictor of ID in pregnancy. If it is used, a higher cutoff value may be more appropriate for diagnosing ID.