Use of Blood Transfusions In Paroxysmal Nocturnal Hemoglobinuria Patients with and without Aplastic Anemia Enrolled In the Global PNH Registry

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare clonal hematopoietic stem cell disease characterized by complement-mediated hemolysis which can lead to life-threatening complications including thrombosis, kidney disease, pulmonary hypertension, pain, anemia, and severe fatigue. PNH clones occur in a number of patients with concomitant aplastic anemia (AA) and other bone marrow disorders (BMD). Some patients with PNH and/or BMD may require red blood cell (RBC) transfusions to treat anemia due to hemolysis or bone marrow hypoplasia.

To characterize the use of RBC transfusions among PNH patients with and without underlying AA.

Enrollment data from 117 clinical sites participating in the observational PNH Registry in 16 countries on 5 continents was analyzed. Patients are included in the Registry regardless of the proportion of cells with deficiency of glycosylphosphatidyl-inositol anchored proteins (GPI-AP), bone marrow pathology, symptoms, or treatments. Sites collect clinical history at enrollment and additional data every 6 months. Demographic data, use of transfusions and other treatments, lab results, and symptoms are summarized for PNH patients with and without AA.

As of June 30, 2010 there were 655 enrolled patients in the Registry (53% female, median age 43). At enrollment, 28% of patients had history of AA and 45% had no history of BMD. Patients with underlying AA had lower median GPI-AP deficient granulocytes than those without BMD (median = 53% vs. 86%, respectively, p<.01) and patients in both groups had similar evidence of hemolytic activity when stratified by clone size (median LDH fold above normal upper limit was 0.90 vs. 0.94, p=.39 for patients with and without AA and clone size <10%; median = 3.41 vs. 4.84, p=.08 for AA vs. no BMD and clone size ≥50%). Not all PNH patients required transfusions: 56% of all patients required transfusions in the year prior to enrollment. Although patients with and without AA were equally likely to be treated with blood transfusions in the year prior to study enrollment overall, some differences emerged when stratified by clone size. For patients with clone size <50%, AA patients were almost twice as likely to receive transfusion in the previous year as patients without BMD (39% vs. 20%, p=.08). However, regardless of underlying AA, the proportion of patients receiving transfusions, in the prior year increased as clone size increased (29%, 31%, and 69% for clone sizes <10%, 10–49%, and ≥50%, respectively, p<.01). When patients were stratified by percent reticulocytes at enrollment (below vs. above the median value of 4.16%), 45% vs. 75% received transfusion in the prior year (p<.01). Among patients receiving a transfusion in the year prior to enrollment, the mean number of RBC units transfused was 9.6 for patients with underlying AA and 7.9 for patients with no BMD (p=.10). However, approximately twice as many patients with AA received 20+ RBC units in that year compared to patients without BMD (20% vs. 11%, p=.09). Number of transfused units in that year was similar by clone size (mean 9.5 vs. 8.6 for clone size <50% vs. ≥50%, p=.57). Concomitant treatment with anticoagulants or immunosuppressants was similar among patients who had received a transfusion in the past year compared to patients with no transfusions (39% vs. 33%, p=.13 and 26% vs. 22%, p=.25 respectively). Patients with AA had more bruising and bleeding while patients without BMD had more hemoglobinuria, dysphagia, and abdominal pain. Transfused patients with AA had more fatigue than non-transfused patients with AA (68% vs. 48%, p=.02).

A substantial proportion (56%) of patients with PNH, but not all, required at least one transfusion in the year prior to enrolling in the registry, independent of underlying AA. The proportion of patients who had at least one transfusion increased with clone size. Among patients who had at least one transfusion, there was a trend for patients with underlying AA to receive more RBC units than patients without BMD. PNH patients with AA have fewer GPI-AP deficient granulocytes but demonstrate elevated hemolysis similar to patients without history of BMD when patients with similar clone sizes were compared. This Global PNH Registry, which remains open to accrual (pnhregistry@iconplc.com), should help to redefine prospectively the long-term natural history of PNH, its treatments, and the outcomes of treatment.

Schrezenmeier: Alexion Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees. Brodsky: Alexion Pharmaceuticals, Inc.: Membership on an entity's Board of Directors or advisory committees. Muus: Celgene: Membership on an entity's Board of Directors or advisory committees; Alexion: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Bessler: Alexion Pharmaceutical Inc: Consultancy; Novartis: Membership on an entity's Board of Directors or advisory committees; Taligen: Consultancy. Szer: Alexion Pharmaceuticals, Inc.: Membership on an entity's Board of Directors or advisory committees. Maciejewski: Celgene: Research Funding; Eisai: Research Funding; Alexion: Consultancy. Socié: Alexion: Honoraria, Membership on an entity's Board of Directors or advisory committees. Urbano-Ispizua: Alexion: Membership on an entity's Board of Directors or advisory committees. Kanakura: Alexion: Membership on an entity's Board of Directors or advisory committees. Hoechsmann: Alexion: Speakers Bureau. Rosse: Alexion: Consultancy, Membership on an entity's Board of Directors or advisory committees. Khursigara: Alexion Pharmaceuticals, Inc.: Employment, Equity Ownership. Karnell: Alexion Pharma International: Employment, Equity Ownership. Bedrosian: Alexion Pharmaceuticals, Inc.: Employment, Equity Ownership. Hillmen: Alexion Pharmaceuticals, Inc: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.