PLATELET ANTIBODY IN IDIOPATHIC THROMBOCYTOPENIC PURPURA AND OTHER THROMBOCYTOPENIAS - A QUANTITATIVE, SENSITIVE, AND RAPID ASSAY

  • 1 January 1980
    • journal article
    • research article
    • Vol. 96  (4) , 640-653
Abstract
Platelet-associated Ig was measured by the use of fluorescent anti-IgG antibody. The method is simple, rapid and sensitive and provides a precise quantitive assay of bound (direct) and free (indirect) IgG with platelet specificity. This test was evaluated in 30 normal volunteers and in 50 patients with immune and nonimmune, treated and untreated thrombocytopenias. All patients with immune thrombocytopenias (acute and chronic idiopathic thrombocytopenic purpura and systemic lupus erythematosus) having platelet counts < 100,000/.mu.l had elevated levels of platelet-bound IgG; 86% had also positive results in the indirect assay. All patients with nonimmunological thrombocytopenias showed normal results in the direct and indirect assay of platelet-associated Ig. In patients studied repeatedly during the course of their illness, an inverse relation was found between platelet count and level of platelet-bound IgG. Patients with systemic lupus erythematosus presented clear exceptions to this rule. Investigations of the absorbability of platelet autoantibodies and alloantibodies showed that this assay can readily differentiate between these 2 antibody species and can also identify specificities of alloantibodies.