title: Absolute Reticulocyte Count Acts as a Surrogate for Fetal Hemoglobin in Infants and Children with Sickle Cell Anemia.
abstract: Hemoglobin switching is largely complete in humans by six months of age. Among infants with sickle cell anemia (HbSS, SCA), reticulocytosis begins early in life as fetal hemoglobin (HbF) is replaced by sickle hemoglobin (HbS). The objective of this study was to determine if absolute reticulocyte count (ARC) is related to HbF levels in a cohort of pediatric SCA patients. A convenience sample of 106 children with SCA between the ages of 1 month and 20 years who were not receiving hydroxyurea or monthly blood transfusions were enrolled in this observational study. Hematologic data, including ARC and HbF levels, were measured at steady state. F-cells were enumerated by flow cytometry. Initial studies compared infants with ARC greater than or equal to 200 K/μL (ARC ≥ 200) based upon the previously reported utility of this threshold as a predictive marker for SCA severity. Mean HbF and F-cell levels were significantly lower in the ARC ≥ 200 group when compared to the ARC < 200 group. Both HbF and F-cell percentages were negatively correlated to ARC in infants and in children between the ages of 1 and 9 years. However, the inverse relationship was lost after the age of 10 years. Overall, decreased expression and distribution of HbF during childhood SCA is well-correlated with increased reticulocyte production and release into the peripheral blood. As such, these data further support the clinical use of reticulocyte enumeration as a disease severity biomarker for childhood sickle cell anemia.
authors.affiliation: Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America; Center for Cancer and Blood Disorders, Children's National Medical Center, Washington, D.C., United States of America; Department of Pediatrics, The George Washington University School of Medicine and Health Sciences, Washington, D.C., United States of America.
authors.forename: Emily Riehm
authors.initials: ER
authors.lastname: Meier
authors.affiliation: Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Colleen
authors.initials: C
authors.lastname: Byrnes
authors.affiliation: Laboratory Medicine Department, Hematology Service, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Maxine
authors.initials: M
authors.lastname: Weissman
authors.affiliation: Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Y Terry
authors.initials: YT
authors.lastname: Lee
authors.affiliation: Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Jeffery L
authors.initials: JL
authors.lastname: Miller
mesh_terms: D000293:Adolescent; D000755:Anemia, Sickle Cell / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005319:Fetal Hemoglobin / Q000378:metabolism*; D006801:Humans; D007223:Infant; D008297:Male; D017701:Reticulocyte Count; D012156:Reticulocytes / Q000166:cytology* / Q000378:metabolism; D055815:Young Adult
chemical_list: D005319:Fetal Hemoglobin