IMMUNE THROMBOCYTOPENIA - USE OF A COOMBS ANTIGLOBULIN-TEST TO DETECT IGG AND C3 ON PLATELETS

We applied a Radio-labeled Coombs antiglobulin test to the diagnosis and management of immune thrombocytopenia in adults and children. This assay substantiated that the majority of patients with idiopathic thrombocytopenic purpura have increased levels of IgG on their platelets. Platelet-associated C3 was elevated in a subset of these patients, some of whom had normal levels of platelet-associated IgG, thus suggesting a role for C3 in the pathogenesis of the thrombocytopenia. The assay enabled us to anticipate a change in clinical status, establish the presence of immunologic remission after splenectomy and propose several mechanisms by which corticosteroids act. Platelets from a patient with the post-transfusion-purpura syndrome also carried increased IgG, indicating a role for IgG antibody or IgG-containing immune complexes in the destruction of host platelets in this disease. The Radio-labeled Coombs test provides a general means to help diagnose, manage and study immune platelet disorders. (N Engl J Med 300:106–111, 1979) THE diagnosis of immune thrombocytopenia can be difficult to establish. The quantitative methods developed by Dixon and Rosse1,2 and Luiken3 and their co-workers to directly assess anti-platelet antibodies have considerably improved the capacity to diagnose immune thrombocytopenia. Nevertheless, since these assays were not primarily developed for clinical use, there appears to be a need for a quantitative assay to readily identify platelet-associated antibody and complement in a clinical setting. The Coombs antiglobulin test is a rapid and sensitive means for diagnosing immune hemolytic anemia by detecting IgG and C3, the third complement component, on the erythrocyte surface. We have developed. © 1979, Massachusetts Medical Society. All rights reserved.