Fluorescein labeled proaerolysin

Fluorescein-labeled proaerolysin (FLAER) is a flow cytometric assay used to diagnose paroxysmal nocturnal hemoglobinuria (PNH). The assay takes advantage of the action of proaerolysin, a prototoxin of aerolysin, a virulence factor of the bacterium Aeromonas hydrophila. Proaerolysin binds to the glycophosphatidylinositol(GPI) anchor in the plasma membrane of cells. Cells affected by PNH lack GPI anchoring proteins, and thus are not bound by proaerolysin. Of note, normal erythrocytes and platelets cannot be used to evaluate for expression of GPI anchoring proteins.