Antiphospholipid antibodies: what is new in 2022

Antiphospholipid syndrome (APS) is a clinicobiological entity defined by the association of thrombotic events and/or obstetric complications and the presence of persistent antiphospholipid antibodies (aPLs) detected by coagulation tests (lupus anticoagulant, LAC) and/or immunological assays (anticardiolipin and anti-glycoprotein-beta-I antibodies). The increased use of direct oral anticoagulants (DOAC) for the treatment of venous thromboembolism (VTE) is now a challenge for hematology laboratories for the diagnosis of APS. DOAC interfere with LAC screening and confirmation tests resulting in a risk of false positive results. To avoid these interferences, several solutions are suggested. Some of them rely on the use of DOAC-reversal systems (activated charcoal tablet, filter system) others on the use of reagents insensitive to DOAC presence in the sample. Detection of anti-phosphatidylserine/prothrombin antibodies may be helpful because they are strongly associated to the presence of LAC and are increasingly recognized as a useful tool in the diagnosis and prognosis of APS. Finally, positivity of LA in the setting of a viral infection is frequent and not specific to APS. During the Covid-19 pandemic, many patients developed arterial and VTE that could suggest testing for aPLs. The association between LAC and a risk of VTE or in-hospital mortality in hospitalized Covid-19 patients was not demonstrated. Moreover, aPLs do not persist after Covid-19. Currently, testing for aPLs in Covid-19 patients is not recommended.