PNH by Flow Cytometry

NOTICE:

The University of Washington Hematopathology laboratory is currently receiving requests for flow cytometry testing that exceed our capacity. We anticipate that turnaround times will be delayed in a subset of MRD flow cytometry cases, and we will no longer be able to regularly provide STAT call backs for MRD flow cases. Additionally, UW Hematopathology is unable to accept flow cytometry reference testing from new clients and will be limiting service to a subset of current clients.

In Paroxysmal Nocturnal Hemoglobinuria (PNH), a clonal marrow stem cell population gives rise to circulating mature hematopoietic cells lacking the expression of a variety of different cell surface proteins whose common feature is their linkage to the cell membrane via a glycosyl-phosphatidyl-inositol (GPI) linkage, a linkage that is deficient in the PNH clone. Similar findings may also be seen in aplastic anemia and myelodysplasia, although the frequency of GPI-deficient cells is lower. GPI-deficiency is most easily assessed in the erythroid, granulocytic and monocytic lineages, and flow cytometry is the method of choice for their detection. The flow cytometric assay evaluates for a loss of expression of the following GPI-linked antigens: CD59 on red cells, CD14 and FLAER on monocytes, and CD24 and FLAER on granulocytes. The assay can detect as little as 0.01% GPI-deficient cells in each cell lineage.