Immunophenotypic characterisation of morphologically diagnosed cases of Acute Myeloid Leukaemia (AML): Immunophenotyping and Aberrant phenotype in AML

Objective: To determine immunophenotypic pattern in newly diagnosed cases of acute myeloid leukaemia by flow cytometry and its correlation with morphological findings.

Methods: This study was conducted at Haematology (Pathology) department, Army Medical College, in collaboration with Immunology Department Armed Forces Institute of Pathology, Rawalpindi from 16 November 2016 to 16 November 2017. One hundred and six patients of both genders and all age groups diagnosed as acute myeloid leukaemia were included in the study. Demographic data was noted. Complete blood counts, bone marrow examination and cytochemical stains were carried out and evaluated microscopically for blast percentage and morphology. Immunophenotyping was performed by flow cytometry using standard panel on peripheral blood or bone marrow samples. The surface and cytoplasmic antigens of interest were analysed and correlated with morphological findings.

Results: The most commonly expressed antigens were CD13, CD33, CD45 and HLA-DR. Almost all blasts expressed CD45 with no remarkable difference among the subtypes of AML. The mean positivity for CD13 among all AML subtypes was 57% and for CD33 was 67%. Aberrant expression of CD7 and CD19 were expressed in 26.4% and 1.1% of all cases respectively. There was concordance rate of 90% between morphology and FCM in our study.

Conclusion: Flow cytometric analysis of acute leukaemia done by a combination of patterns and intensity of antigen expression improves diagnostic yield in AML. CD13, CD33 and CD45 are the most frequently expressed antigens in AML. Our findings suggest a 90% concordance between morphology and flow cytometry. It is pertinent to conclude that flow cytometry results interpreted with morphology are complementary.