Fc III receptors (FcRIII) on granulocytes: a specific and sensitive diagnostic test for paroxysmal nocturnal hemoglobinuria (PNH).

The FcRIII on human granulocytes is a glycosyl-phosphatidylinositol-anchored membrane protein. In PNH, proteins with this type of membrane linkage are known to be deficient on blood cells. The purpose of this study was to assess the diagnostic value of flow cytometric FcRIII quantification on granulocytes in PNH. Immunofluorescence measurements were performed in 105 patients, including 7 patients with PNH, 16 patients with aplastic anemia, and 12 with myelodysplastic syndrome, by a whole blood immunofluorescent staining procedure using monoclonal antibodies to FcRIII. In all 7 PNH patients and in 3 patients with aplastic anaemia, a distinct FcRIII-deficient granulocyte population of variable size was found. None of the remaining patients showed a similar population of FcRIII-deficient granulocytes. Quantification of FcRIII-deficient neutrophils is shown to be a highly specific and sensitive diagnostic test for PNH. It is easy, fast and highly reproducible and, therefore, suitable for routine diagnostic and follow-up studies in PNH patients and patients with aplastic anemia.