Background/Purpose: In some antiphospholipid syndrome (APS) patients, the antiphospholipid antibodies (aPL) becomes persistently negative. Discontinuation of anticoagulation has been proposed, however the long term follow-up after negativization is uncertain.The purpose of this study is to evaluate the clinical outcome after aPL negativization in primary APS patients.

Methods: From a cohort of 70 patients diagnosed with primary APS, we selected patients with positive aPL determinations at onset and ≥2 subsequent negative aPL determinations during the last 5 years. In order to corroborate the immunologic profile, a cross-sectional analysis was made. We determined IgG/IgM aCL antibodies, IgG/IgM antiβ2GPl, anti-annexin A5 antibodies (Enzyme Linked Immunosorbent Assay,ELISA) and lupus anticoagulant (LA) (Russell viper venom). All patients continued treatment with oral anticoagulants. We reviewed clinical charts to obtain clinical data and aPL determinations at onset and after negativization. Statistical analysis: descriptive statistics and Kaplan-Meier analysis.

Results: We found 24 patients with persistently negative aPL, including the last immunologic profile, 17 females, 7 males, mean age 51.7, disease evolution 16.3 years, mean of 4 aPL previous positive determinations. aCL was found positive at onset in 87.5% and 21% had double aPL positivity at onset (aCL/LA). Deep venous thrombosis (DVT) was the most frequent manifestation at onset in 33%,ischemic stroke in 29% and pulmonary embolism in 12%. INR range: 2-3.The most frequent concomitant cardiovascular risk factors were dyslipidemia (29%), overweight (20.8%) obesity (16.7%). Mean time with aPL positive 109.4± 80.7 months. The median of thrombotic events was 2 (range 2-19). After 60 months of follow-up since negativization of aPL, Kaplan-Meier analysis: 40% of patients presented thrombosis recurrence, of these, DVT was observed in 29.2%, and ischemic stroke in 4,2%, despite optimal anticoagulant treatment. Other non-thrombotic APS manifestations were chronic ulcers in lower extremities in16.7%, and severe thrombocytopenia in 8%

Conclusion: This study suggest, that in primary APS, persistent negativization of aPL, is not an indication to interrupt oral anticoagulant therapy. Additional risk factors and other aPL can contribute to the recurrence of thrombosis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/recurrence-of-thrombosis-despite-negativization-of-antiphospholipid-antibodies-in-primary-antiphospholipid-syndrome-a-follow-up-to-5-years/