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Objective We aimed to analyse the prevalence of non-criteria anti-phospholipid (aPL) antibodies and their role in the diagnosis, treatment and prognosis in a cohort of patients with clinical features consistent with a diagnosis of antiphospholipid syndrome (APS), but persistently negative for criteria aPL – anti-cardiolipin antibodies (aCL), anti-β2-glycoprotein I antibodies (aβ2-GPI) and lupus anticoagulant (LA) – named seronegative APS (SN-APS). Methods Sera from SN-APS patients were tested for aCL by TLC-immunostaining, anti-vimentin/cardiolipin (aVim/CL) and anti-phosphatidylserine/prothrombin (anti-PS/PT) by ELISA. Control groups of our study were APS patients and healthy controls. Results We enrolled 114 consecutive SN-APS patients, 69 (60.5%) resulted positive for at least one non-criteria test in two occasions 12 weeks apart. Among the persistently positive patients to these tests, 97% resulted positive for aCL by TLC-immunostaining, 52.3% for aVim/CL and 17.4% for aPS/PT. SN-APS patients with double positivity (aCL by TLC-immunostaining and aVim/CL) showed a likelihood positive ratio of 8 to present mixed thrombotic and obstetrical features. Among SN-APS patients tested positive, after the therapeutic changes, three cases of recurrent thrombosis were observed [median follow-up 41 months (IQR 39.5)]. Twenty pregnancies were recorded in 17 SN-APS patients after the detection of unconventional aPL and 12 of them (60%) experienced a good outcome under conventional treatment for APS. Conclusions This is the largest monocentric study demonstrating that aCL tested by TLC-immunostaining and aVim/CL can detect aPL positivity in SN-APS. It may encourage clinicians to monitor and provide adequate targeted therapy, which improve SN-APS prognosis. [ABSTRACT FROM AUTHOR]

Objectives To compare clinical features, laboratory data and fetal-maternal outcomes between 1000 women with obstetric APS (OAPS) and 640 with aPL-related obstetric complications not fulfilling Sydney criteria (non-criteria OAPS, NC-OAPS). Methods This was a retrospective and prospective multicentre study from the European Registry on Obstetric Antiphospholipid Syndrome. Results A total of 1650 women with 5251 episodes, 3601 of which were historical and 1650 latest episodes, were included. Altogether, 1000 cases (OAPS group) fulfilled the Sydney classification criteria and 650 (NC-OAPS group) did not. Ten NC-OAPS cases were excluded for presenting thrombosis during follow-up. All cases were classified as category I (triple positivity or double positivity for aPL) or category II (simple positivity). Overall, aPL laboratory categories showed significant differences: 29.20% in OAPS vs 17.96% in NC-OAPS (P < 0.0001) for category I, and 70.8% in OAPS vs 82% in NC-OAPS (P < 0.0001) for category II. Significant differences were observed when current obstetric complications were compared (P < 0.001). However, major differences between groups were not observed in treatment rates, livebirths and thrombotic complications. In the NC-OAPS group, 176/640 (27.5%) did not fulfil Sydney clinical criteria (subgroup A), 175/640 (27.34%) had a low titre and/or non-persistent aPL positivity but did meet the clinical criteria (subgroup B) and 289/640 (45.15%) had a high aPL titre but did not fulfil Sydney clinical criteria (subgroup C). Conclusion Significant clinical and laboratory differences were found between groups. Fetal-maternal outcomes were similar in both groups when treated. These results suggest that we could improve our clinical practice with better understanding of NC-OAPS patients. [ABSTRACT FROM AUTHOR]

A correction to the article "Comparative study of obstetric antiphospholipid syndrome (OAPS) and non-criteria obstetric APS (NC-OAPS): report of 1640 cases from EUROAPS registry" is presented.