Flow Cytometric Immunophenotyping of Acute Leukaemia at the University College Hospital, Ibadan, South West Nigeria: A Five-Year Analysis

This study analyses five years of flow cytometric immunophenotyping data for acute leukaemia cases at the University College Hospital (UCH), Ibadan, South West Nigeria, examining the distribution of leukaemia subtypes, immunophenotypic patterns, and their clinical correlates in the Nigerian context. Flow cytometry remains the cornerstone of acute leukaemia classification, yet Nigerian immunophenotyping data are limited to small single-centre case series that do not adequately represent the true disease landscape. A retrospective analytical study reviewed all acute leukaemia cases from January 2019 to December 2023, extracting immunophenotypic, morphological, and clinical data for 220 cases. All cases were classified according to the 2022 WHO haematopoietic tumour classification. Acute myeloid leukaemia (AML) constituted 62 percent, B-lymphoblastic leukaemia (B-ALL) 29 percent, and T-ALL 9 percent. Aberrant antigen co-expression was identified in 38 percent of all cases, complicating lineage assignment. CD34 negativity in AML was associated with a more differentiated phenotype and more frequent monocytic differentiation. Paediatric cases (below 15 years) were predominantly B-ALL (68%), while adult patients had predominantly AML (74%). CD56 expression in AML correlated with worse haematological response at six weeks. NK-cell immunophenotypes were present in 2.7 percent of cases, associated with aggressive clinical courses. These data provide the first five-year systematic immunophenotyping analysis from a West African teaching hospital and establish a local leukaemia subtype distribution framework. Keywords: flow cytometry, immunophenotyping, acute leukaemia, UCH Ibadan, leukaemia classification.