Differential Cell Count of Bone Marrow Aspirates in Steady-state Sickle Cell Anaemia Patients

Summary Background: Megaloblastic arrest of the bone marrow is one of the causes of anaemic crises in patients with sickle cell anaemia. The diagnosis of this condition will require that the reference level of megalobalastosis during steady state be properly documented. Objectives: To document a reference differential cell count in the bone marrow aspirates of patients with sickle cell anaemia and determine the level of megaloblastosis that can be regarded as indicating megaloblastic crisis in such patients. Design: Systematic counting of haematopoietic cells in the bone marrow of children with confirmed Hb phenotype SS who are in steady state. Subjects and Methods: The subjects were 11 of 68 children with sickle cell anaemia attending the paediatric outpatient clinic at the Lagos University Teaching Hospital, Lagos, in respect of whom parental consent for bone marrow aspiration was obtained. About 4.5 ml of blood was obtained from the antecubital vein of each child, for full blood count. Bone marrow was aspirated from the posterior superior iliac spine. Slides were stained with MayGrünwald-Giemsa stain. Proportions of erythroid, myeloid, lymphoid and megakaryocytic cells out of 250 nucleated bone marrow cells were determined. Results: Steady state mean packed cell volume (PCV) was 0.2 +0.017 L/L. The mean reticulocyte count was 5.9 percent (95% CI, 5.3 - 7.0%) and the mean cell volume was 91.8 £ 2.7 fl. Erythroid precursors constituted 34.5 percent of the total nucleated bone marrow cells (NBMC). Of these, polychromatic and orthochromatic erythroid blasts predominated, constituting 49 and 36 percent respectively, of total erythroid precursors. Polychromatic and orthochromatic megaloblasts constituted 16.5 percent (95% CI, 7-25%) of total NBMC or 47.8 percent of erythroid precursors. The myeloid erythroid ratio was 1:1. The reference range of megaloblasts was 8-26 percent of the NBMC. Conclusion: Patients with sickle cell anaemia in steady-state may show megaloblastic bone marrow, changes even with routine folate supplements. Megaloblastic crisis should not be diagnosed until megaloblasts are in excess of 26 percent of the total NBMC.