A gel microtyping system for diagnosis of paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH), an acquired stem cell defect, is underdiagnosed because of its atypical symptoms in some patients and because available methods, which are time consuming and complicated, are not widely used. The hemolysis of PNH red blood cells (RBCs) is attributed to their enhanced susceptibility to complement lysis caused by a deficiency in glycosylsphosphatidylinositol (GPI)-anchored complement regulatory membrane proteins, especially membrane inhibitor of reactive lysis (MIRL [CD59]). We evaluated the diagnostic value of a simple hemagglutination test using the gel microtyping system by comparing it with lytic tests (the Ham test and the sucrose lysis test) and with flow cytometry (FC) assessment of expression of GPI-anchored proteins (CD59 and CD55). Examining 51 blood samples from 48 patients, we found that the gel test is useful as a screening test for PNH diagnosis and can replace the Ham test and the sucrose lysis test. The threshold of the gel test is about 10 percent of defective RBCs detected by FC. It should, however, be supplemented with FC so as to analyze precisely the defective RBCs and granulocytes in patients with positive gel test results, and, in case of negative results, to detect a small clone of defective cells in atypical cases. Due to the simplicity of the gel test, its wide use can facilitate the diagnosis of PNH.