Antiplatelet antibodies in cases of Glanzmann's thrombasthenia with and without a history of multiple platelet transfusion.

Antiplatelet antibodies are known to be present in a wide spectrum of patients, which include chronic Idiopathic Thrombocytopenic Purpura (ITP), infections, etc., including Glanzmann's thrombasthenia (GT) patients who receive multiple platelet transfusions. The presence of natural antibodies to platelet receptors is not studied in cases of GT. We studied the antiplatelet antibodies in 23 patients with GT, 15 of which had received multiple transfusions and eight that had not received transfusions, along with 50 cases of chronic ITP. The prevalence and specificity of platelet-bound antibodies were detected by inhibition assays using O-group platelets on flow cytometry. The mean antiplatelet antibodies in 15 patients of GT who had not received transfusions and eight patients with multiple transfusions was 8427 + 2131.88 and 9038 + 2856 antibodies/platelet, respectively, while in case of the 50 ITP patients studied, it was 22166 + 5616 antibodies/platelet (Normal Range 1500–3200 antibodies/platelet). We conclude that GT patients who have not received transfusions may develop antiplatelet antibodies to the missing/abnormal receptor. Whether this is due to a molecular mimicry or due to some other mechanism needs to be explored.

Detection of Platelet Specific Antibodies by Modified Antigen Capture ELISA Test / 대한진단검사의학회지

BACKGROUND: Autoimmune thrombocytopenia (AITP) is characterized by autoantibody-induced platelet destruction. Although several studies have shown that pathogenic autoantibodies are mainly IgG directed platelet glycoproteins (GP), a platelet GP specific test is not available in clinical laboratories. The aim of this study was to evaluate the clinical usefulness of a Modified Antigen Capture Enzyme-linked immunosorbent assay (MACE) test in the diagnosis of AITP. METHODS: We investigated fifty-seven patients who showed a platelet count lower than 100 x 10(9)/L and underwent a bone marrow examination. They were classified into primary AITP (P-AITP) (n=21), secondary AITP (S-AITP) (n=15), and non-immune thrombocytopenia (NITP) (n=21) by bone marrow findings and clinical diagnosis. Platelet GP (IIb/IIIa, Ia/IIa, Ib/IX, IV)-specific antibodies and anti-HLA class I antibody were detected by MACE test. RESULTS: Among 57 samples, platelet GP specific antibodies were detected in 8 (22.2%) of 36 patients with AITP and 1 (4.8%) of 21 patients with NITP. The specificities were as follows: GP IIb/IIIa (n=4), GP Ia/IIa (n=5), GP Ib/IX (n=3) and GPIV (n=2). Of the nine patients with platelet GP specific antibodies, four (44.4%) had more than two platelet GP specific antibodies. The sensitivity, specificity, positive predictive value and negative predictive values of the MACE test for AITP were 22.2%, 95.2%, 88.9%, 41.7%, respectively. A previous transfusion history was associated with a higher detection rate of anti-HLA class I antibodies (P<0.05). CONCLUSIONS: The MACE test is a convenient method to detect platelet GP specific antibody and is very specific to diagnose AITP. In clinical practice, even though it is not sensitive, the MACE test would be useful in differentiating AITP from NITP.