Background The rate of antiphospholipid antibody (aPL) negativization in antiphospholipid syndrome (APS) patients is uncertain, but it is estimated to be as high as 8%. Currently, a consensus definition of aPL negativization is lacking, as well as international recommendations on how to approach treatment in patients with a persistent aPL-negative seroconversion. Aim The aim of the Delphi survey was to evaluate the clinical approach and level of consensus among experts from the APS Study Group of the Italian Society for Rheumatology (SIR-APS) in different clinical scenarios. Methods Experts of SIR-APS were contacted using a survey methodology. Results A structured survey was circulated among 30 experts. Up to 90% of the interviewed experts agreed on defining aPL negativization as the presence of two negative determinations, 1 year apart (90%). Almost full consensus exists among experts in some clinical settings, including: (1) the role of aPL negativization in the management of a thrombotic event determined by concomitant presence of cardiovascular risk factors, both modifiable and not modifiable (90%); (2) approach to young patients with triple aPL positivity who experienced pulmonary arterial thrombotic events and tested negative for aPL detection after 5 years of vitamin K antagonist (VKA) treatment (90%); (3) the use of " extra criteria " aPL antibody testing before pondering VKA suspension (93%). Conclusion A substantial agreement exists among experts on how to define aPL negativization. VKA suspension should be embraced with extreme caution, particularly in case of previous thrombotic events and/or triple aPL positivity. Nevertheless, VKA cessation might be considered when risk factors are carefully monitored/treated and the presence of " extra criteria " aPL is ruled out.
