title: Prospective evaluation of the clinical usefulness of an antigen-specific assay (MAIPA) in idiopathic thrombocytopenic purpura and other immune thrombocytopenias.
abstract: The diagnosis of idiopathic immune thrombocytopenia remains a clinical diagnosis based on the exclusion of other causes of immune and nonimmune thrombocytopenia. Measurement of platelet-associated Ig (PAIg), while sensitive, is nonspecific for the diagnosis of immune thrombocytopenia. Published experience of antigen capture assays (including monoclonal antibody immobilization of platelet antigens or MAIPA) suggest a high sensitivity and specificity (70% to 80%) in selected groups of patients. In a prospective evaluation of 158 patients with thrombocytopenia from all causes, we report a sensitivity of 51% and specificity of 80% for direct MAIPA assays. MAIPA was considerably better in discriminating immune from nonimmune thrombocytopenia than two assays of PAIgG. Antiplatelet antibodies detected by MAIPA were more frequently directed against the glycoprotein (GP) IIb/IIIa than the GP Ib/IX complex. Our experience suggests that MAIPA assays are useful in the laboratory assessment of thrombocytopenia, should be performed before therapy, and that some patients with 'nonimmune' thrombocytopenia may have genuine antiplatelet antibodies.
authors.affiliation: Department of Hematology, Prince of Wales Hospital, University of New South Wales, Randwick, Sydney, Australia.
authors.forename: T A
authors.initials: TA
authors.lastname: Brighton
authors.forename: S
authors.initials: S
authors.lastname: Evans
authors.forename: P A
authors.initials: PA
authors.lastname: Castaldi
authors.forename: C N
authors.initials: CN
authors.lastname: Chesterman
authors.forename: B H
authors.initials: BH
authors.lastname: Chong
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D016824:Antigens, Human Platelet / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology*; D001327:Autoimmune Diseases / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D003937:Diagnosis, Differential; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D006801:Humans; D010980:Platelet Membrane Glycoproteins / Q000276:immunology*; D011446:Prospective Studies; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013921:Thrombocytopenia / Q000097:blood / Q000139:chemically induced / Q000209:etiology / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D016824:Antigens, Human Platelet; D001323:Autoantibodies; D001324:Autoantigens; D010980:Platelet Membrane Glycoproteins