Role of Immature Reticulocytes as an Early Indicator of Engraftment in Bone Marrow Transplantation in Thalassemia Major Patients

Background: Absolute neutrophil count (ANC) is the conventional indicator of bone marrow engraftment. Recently, new reticulocyte parameters like Immature Reticulocyte Fraction (IRF) and High Fluorescence Reticulocyte (HFR) have been used as new markers of engraftment. HFR provides a very early and sensitive index of marrow erythropoietin activity. Our aim is to study the role of Immature Reticulocyte parameters as early indicators of engraftment in BMT patients.Methods: In this hospital-based prospective observational study, all allogenic BMT cases of thalassemia major (n=30) were recruited over 18 months period. Complete blood count (CBC) parameters including ANC, Absolute monocyte count (AMC), Absolute reticulocyte count, Reticulocyte%, IRF and HFR were determined from the day before the BMT, the infusion day (day 0), and thereafter on a daily basis until achievement of engraftment (ANC >500/µl).Results: Out of 30 cases, 26 patients achieved engraftment. The mean day of achievement of ANC>500/ul was 20.77 (median day 20) and IRF>10% was 15.39 ± 4.34 (median day 16). Median day of IRF was achieved 4 days before ANC. Mean day of HFR>3% was 15.25 (Median day 14). Median day of HFR was achieved 6 days before ANC. These correlations were significant (P value10%, HFR >3% and AMC >100/μl should be routinely used to trace hematopoietic restoration after BMT because these parameters preceded standard neutrophil recovery (ANC >500/μl) which is a traditional marker of engraftment after BMT.