Application of Hematologic Indices for Diagnosis of Iron Deficiency Anemia in Pregnancy [ID: 1378030]

INTRODUCTION: Prenatal care providers may omit iron studies if the complete blood count is suggestive of mild or moderate iron deficiency anemia (MMIDA). We investigated how sensitive the mean corpuscular volume (MCV) or red blood cell distribution width (RDW) are in identifying MMIDA that is diagnosed by ferritin measurement. METHODS: This IRB-approved retrospective cohort study from October 15, 2007 to October 14, 2021, included singleton pregnancies diagnosed with MMIDA and treated with iron for at least 4 weeks prior to delivery. Patients with comorbidities that predispose to anemia (eg, thalassemia) were excluded. The primary outcome was the percentage of patients whose MMIDA could be identified by low MCV or elevated RDW. Secondary outcomes included changes in hemoglobin, MCV, and RDW, and were assessed by persistence versus correction of MMIDA by delivery. RESULTS: Eight thousand eight hundred thirty-three patients met criteria; 1,141 (12.9%) had MMIDA diagnosed by low ferritin. The MCV or RDW was concordant with MMIDA diagnosis in 259 (22.7%). Hemoglobin significantly improved from 10.6 to 11.8 g/dL in the corrected group and did not change in the persistent group. Treatment with concurrent oral and IV iron resulted in greater hemoglobin increase (persistent, +0.4, versus corrected, +1.9 g/dL) versus oral iron alone (−0.1 versus +1.3 g/dL). The MCV decreased and RDW increased in both persistent (−2.7 fL, +1.0%) and corrected groups (−0.8 fL, +0.7%). CONCLUSION: Thirteen percent of providers ordered iron studies when MMIDA was suspected. Low MCV or elevated RDW are insensitive surrogates of ferritin. Iron studies remain the gold standard for diagnosis. Concurrent IV iron results in superior improvement of hemoglobin versus oral iron alone.