OPTIMA 試験：高精度フローサイトメトリー法によるGPI アンカー膜蛋白欠損血球の検出

抄録

Paroxysmal nocturnal hemoglobinuria (PNH) is a hematologic disorder characterized by the clonal expansion of hematopoietic stem cells that are incapable of glycosylphosphatidylinositol (GPI) -anchor biosynthesis, due to an acquired somatic mutation in the phosphatidylinositol glycan class A-gene. The detection of GPI-anchored protein deficient cells by flow cytometry (FCM) is essential for the diagnosis of PNH. Moreover, it helps to predict response to immunosuppressive therapy in patients with bone marrow failure (BMF) such as aplastic anemia (AA). However, the clinical significance of such PNH-type cells has not been assessed in a multi-centered, large-scale study. A nationwide multi-center prospective observational study (OPTIMA study) was conducted to determine the prevalence of increased PNH-type cells and its correlation with prognosis in patients who develop BMF. PNH-type cells were detected with a high-resolution FCM method with liquid fluorescent aerolysin and antibodies against CD55 and CD59 that was established by Kanazawa University. The sensitivity and specificity of the assay (granulocytes, ≧0.003%; erythrocytes, ≧0.005%) were validated by six laboratories using a positive sample containing 0.01% PNH-type cells as well as a negative sample from a healthy individual. Of 664 cases examined so far, 240 (36.1%) had PNH-type cells and 76 (11.4%) had ≧1% PNH-type cells. In patients who had ≧1% PNH-type cells, 50% showed lactate dehydrogenase levels ≧1.5×upper limits of normal cases. Thus, we confirmed the feasibility for different laboratories to detect PNHtype cells less than 0.1% precisely with a standardized high-resolution FCM method.