Assessment of the clinical relevance of isolated aPTT-LA positivity in the diagnosis of Antiphospholipid Syndrome.

• Grant number: 25/07064-1
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: July 01, 2025
• End date: June 30, 2026
• Field of knowledge: Health Sciences - Medicine - Medical Clinics
• Principal Investigator: Fernanda Loureiro de Andrade Orsi
• Grantee: Julia Noumi Mellis
• Host Institution: Centro de Hematologia e Hemoterapia (HEMOCENTRO). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Associated research grant: 22/13216-0 - Crosstalk between hemostasis and innate immunity (Immunothrombosis): pathogenic, diagnostic and therapeutic implications in infectious and inflammatory diseases, AP.TEM

Abstract

Antiphospholipid Syndrome (APS) is a systemic autoimmune disease characterized by the persistent positivity of one or more antiphospholipid antibodies (aPL), that recognize phospholipid-binding proteins such as ¿2-glycoprotein I (¿2GPI). This binding triggers the activation of inflammatory and prothrombotic cells, significantly increasing the risk of thrombosis and obstetric complications. The treatment of APS, particularly in its thrombotic form, is primarily based on long-term anticoagulation, while laboratory diagnosis relies on the detection of aPL through specific tests, including the lupus anticoagulant (LA), anticardiolipin antibodies (aCL), and anti-¿2-glycoprotein I antibodies (a¿2GPI). This study aims to evaluate whether patients with isolated positivity for the activated partial thromboplastin time sensitive to lupus anticoagulant (aPTT-LA) present clinical manifestations similar to patients with positive in more specific tests for aPL detection, such as the diluted Russell's viper venom test (dRVVT), aCL, and a¿2GPI. In this context, it is necessary to improve the specificity of laboratory diagnoses in APS, particularly considering the lower stability of aPTT-LA in relation to the dRVVT, which makes its isolated positivity questionable. This would enable a more accurate interpretation of test results, reducing the risk of misdiagnosis and, consequently, inappropriate therapeutic approaches. Patients diagnosed with primary thrombotic APS, according to the Sydney classification criteria, who have had at least one thrombotic event confirmed by imaging, laboratory, or histopathological evidence, will be included. At the end of the study, it is expected to determine the prevalence of isolated aPTT-LA positivity in patients with APS and positive LA test, and to compare its association with laboratory profiles, clinical characteristics, and thrombotic events. (AU)