CO093 | PROGNOSTIC ROLE OF ANTIPLATELET ANTIBODY TESTING IN IMMUNE THROMBOCYTOPENIA

G. Maraziti, C. Schiavone, A. Fiaccadori, A. Mezzasoma, C. Becattini | Internal and Emergency Medicine - Stroke Unit, S. Maria della Misericordia Hospital – University of Perugia, Perugia, Italy

Background and Aims. Antiplatelet antibody (APA) testing is considered an adjunct laboratory tool in the diagnosis of immune thrombocytopenia (ITP). The prognostic role of APA testing remains undefined. We aimed to assess the prognostic value of APAs in patients with ITP.
Methods. We conducted a retrospective study including patients referred for APA testing using the glycoprotein-specific indirect MAIPA assay (anti-GpIIb/IIIa, anti-GpIa/IIa, and anti-GpIb/IX) and subsequently diagnosed with ITP (February 2023-October 2025) at our center. Study outcomes were major bleeding (MBs), defined as moderate-to-severe bleeding according to the ISTH bleeding assessment tool, and thromboembolic events (TEs), defined as one among objectively confirmed acute coronary syndrome, ischemic stroke or TIA, proximal deep vein thrombosis, unusual site thrombosis, or pulmonary embolism, occurring within 30 days from the onset of acute thrombocytopenia. Remission was defined as a platelet count >100,000/µL for at least one month.
Results. A total of 336 patients with an ITP diagnosis were included, 75 with primary and 261 with secondary ITP. APAs were detected in 37.3% of primary and 47.1% of secondary ITP patients. One, two, and three positive APAs were detected in 22.7%, 10.7%, and 4.0% of primary ITP and in 24.9%, 17.2%, and 5.0% of secondary ITP, respectively. The most prevalent APA was anti-GpIIb/IIIa (35.1%), followed by anti-GpIa/IIa (27.1%) and anti-GpIb/IX (8.0%). MBs occurred in 46 patients (13.7%), TEs in 21 (6.2%), and remission in 170 (50.6%). No association was found between MBs and the presence, number, or type of APAs. Anti-GpIb/IX positivity was independently associated with TEs (OR 6.43, 95% CI 1.82–22.27; p=0.003). APAs were independently associated with lower odds of remission (OR 0.54, 95% CI 0.32–0.91; p=0.021), mainly driven by anti-GpIa/IIa (OR 0.45, 95% CI 0.23–0.86; p=0.017).
Conclusions. In our cohort of ITP patients, indirect MAIPA-based APA positivity—particularly anti-GpIa/IIa—was associated with reduced probability of remission but not with the risk of MB. The observed association between anti-GpIb/IX antibodies and TEs warrants confirmation in further studies.