Differential usefulness of various markers in the flow cytometric detection of paroxysmal nocturnal hemoglobinuria in blood and bone marrow

In this study, we examined the usefulness of various markers on blood cell populations in the diagnosis of paroxysmal nocturnal hemoglobinuria (PNH). We also evaluated bone marrow specimens, which generally are considered less suitable than blood owing to variable expression of glycosyl phosphatidylinositol (GPI)-linked antigens during hematopoietic cell differentiation. All 15 patients in our cohort had subpopulations of CD16/CD55-deficient granulocytes and CD14/CD55-deficient monocytes ("PNH clones"). The PNH clone size of granulocytes and monocytes was greater than that of erythrocytes or lymphocytes in the majority of the cases. It is interesting that CD59 showed limited usefulness for detecting PNH+ monocytes. Normal monocytes exhibited significantly dimmer CD59 expression than normal granulocytes. PNH-deficient monocytes expressed only marginally lower CD59, making it a less robust marker for highlighting PNH+ monocytes compared with CD14 or CD55. Finally, our study demonstrated the definitive usefulness of a limited combination of markers (CD16/CD55/CD45/CD14) in detecting GPI-deficient monocytes and granulocytes in bone marrow specimens submitted for flow cytometric evaluation of cytopenias.