Red cell distribution width and reticulocyte hemoglobin content as predictors of iron depletion in children with cyanotic congenital heart disease

Background: Iron-deficiency anemia is challenging to diagnose in patients with cyanotic congenital heart disease (CCHD) because of the high hemoglobin concentration as a compensatory mechanism for cyanosis. Purpose: This study aimed to identify predictive parameters of iron depletion status and assess the prevalence of iron deficiency in patients with CCHD. Methods: A descriptive study enrolled patients with CCHD aged 6 months to 15 years between September 2022 and September 2023. Participants were categorized into iron depletion and iron sufficiency groups defined by a serum ferritin level <30 ng/mL or transferrin saturation <15%. The clinical characteristics and laboratory parameters were compared between groups. The Youden index was used to determine the optimal cutoff points, maximizing both sensitivity and specificity for the red cell indices. Results: Among the 110 enrolled patients with CCHD, 28 (25.5%) had iron depletion. While hemoglobin (Hb) and hematocrit (Hct) levels were comparable between groups, the iron-depleted group exhibited significantly lower reticulocyte hemoglobin content (CHr) and higher red cell distribution width (RDW). A multivariate analysis identified an RDW ≥18.8% (odds ratio [OR], 7.79; P=0.001) and CHr <28 pg (OR, 4.97; P=0.004) as independent predictors of iron depletion. The diagnostic accuracy improved to 85.4% when these parameters were combined. Conclusion: Iron depletion is highly prevalent in patients with CCHD. Because conventional parameters, such as Hb and Hct, fail to differentiate iron status owing to compensatory mechanisms, CHr and RDW serveas effective predictive tools. This combination offers a practical diagnostic alternative, especially in resource-limited settings, where standard iron studies are unavailable.