Pseudothrombocytopenia: An Immunologic Study on Platelet Antibodies Dependent on Ethylene Diamine Tetra-Acetate

Antibodies specifically reacting with platelets only in the presence of EDTA. by the platelet immunofluorescence test. were found in the serum of 20 patients with pseudo-thrombocytopenia due to in vitro EDTA-dependent platelet agglutination. These antibodies reacted optimally at 0-4’C. In 1 9 patients. IgG antibodies were detected; in 8 patients. 1gM or IgA antibodies were also found. In one patient. only IgM antibodies were found. In 14 patients. the lgG anti-bodies were IgGi. but lgG2. lgG3. and lgG4 antibodies P SEUDOTHROMBOCYTOPENIA is a phenom-enon in which antibodies, present in the patients’ sera, react with platelets in blood anticoagulated with EDTA, causing agglutination and a spuriously low platelet count.’ The platelet suspension immunofluorescence test (PSIFT), developed in our laboratory, enabled us to study the mechanism of the EDTA-dependent platelet agglutination in more detail. In this article we present the results of these investigations