DOAC Versus VKA in Patients With Non-high-risk APS : Prospective Cohort Study

Antiphospholipid syndrome (APS) is a thrombotic disease requiring prolonged anticoagulation. Direct oral anticoagulants (DOACs) are indicated as 1st-line therapy in venous thrombosis, compared with VKAs, due to their easier handling and lower bleeding risk for equivalent efficacy. In APS, VKAs are still the reference treatment. However, DOACs are generally introduced in the acute phase of venous, before the diagnosis of APS. VKA have the disadvantage of numerous food and drug interactions, and therefore require close monitoring of INR, at least once a month. Because they are easier to use than VKAs, and the risk of bleeding is lower, patients are often reluctant to switch from DOACs to VKA. Studies have shown that APS patients with high thrombotic risk (positivity of all three antiphospholipid tests, history of arterial or small vessels thrombosis or cardiac valve damage) have an increased thrombotic risk during DOACs vs. VKA treatment. Since 2020, the ISTH guidelines have suggested avoiding DOACs in high-risk APS, but suggest continuing theim in other patients if they were introduced for venous thrombosis and if follow-up on DOACs is reassuring. In the case of high-risk APS patients, the relay is therefore systematic. For non-high-risk patients (the majority), there are no data to justify systematic switch. Given the quality-of-life advantages of DOACs over VKAs, patients are not always in favor of changing their anticoagulant therapy, especially if they have been on it for many years with good tolerability. For these reasons, a number of patients with non-high-risk APS remain on DOACs. Nevertheless, the limited data available on the efficacy of DOACs in non-high-risk patients are of low level of evidence and contradictory. In 2020, a literature review of non-high-risk SAPL patients treated with DOACs reported that 8.6% of them experienced thrombotic recurrence within 12 months, with no possible comparison with VKAs. A recent retrospective study with 96 patients reported that 15.4% of patients treated with DOACs had a recurrence, compared to 5.3% on VKAs. However, this difference was not statistically significant (p=0.15) due to a clear lack of power. The objective is to determine the frequency of thrombotic recurrences and to compare it according to the type of oral treatment, anti-Xa versus VKA, in non-high-risk APS, through a cohort study with prospective follow-up. The patient's usual antithrombotic treatment, DOAC and VKA, will be continued unchanged.

prospective cohort of APS patient treated with VKA or DOACs (specially oral Xa treatment). APS patients will be non high risk patients (no triple positivity, any previous arterial or small vessels thrombosis or cardiac involvment). the treatment taken by the patient at inclusion will not be modified. There will therefore be no change to the patient's usual management. all patients will have a blood sample taken at inclusion as part of a routine blood test. Patients will be prospectively follow up and the level of recurrence thrombotic event will be recorded