Non-criteria Antiphospholipid Antibodies: a narrative review

Viewpoint: The value of non-criteria antiphospholipid antibodies

In 2006, at a meeting in Sydney, Australia, consensus was reached by an international group of specialists to establish a number of serological criteria that identify patients with a history of thrombosis or pregnancy complications as having antiphospholipid syndrome (APS). These criteria were originally formulated for research purposes and to compare clinical trials in different centres. However, these same criteria are now generally used and accepted for the diagnosis and treatment of patients. The practice of using these criteria for direct patient care requires that these criteria are based on sound scientific evidence. Indeed, for all the autoantibodies that are officially included in the serological criteria, it has been shown that they induce thrombosis and fetal loss when infused into mice. There are also a number of additional autoantibodies that have been identified in these patients but for these antibodies there was not enough evidence to meet the official APS criteria in 2006. Seventeen years have now passed since the consensus meeting, therefore, this review examines whether additional studies performed with these 'non-criteria' autoantibodies have provided sufficient results to suggest the inclusion of these autoantibodies in the official serological criteria of APS.

Are antiphospholipid antibodies just a common epiphenomenon or are they causative of immune-mediated coagulopathy in COVID-19?

The coronavirus disease 2019 (COVID-19) is the largest public health emergency in recent times. A significant number of patients develop a severe form of COVID-19 characterized by coagulopathy, organ failure, and elevated mortality. In addition, an unusually high frequency of antiphospholipid antibodies (aPLs) has been found in patients with COVID-19. These clinical and serological manifestations closely resemble those seen in the antiphospholipid syndrome (APS), especially in its catastrophic form, suggesting a role of aPLs in immune-associated coagulopathy. However, government bodies such as the American Society of Hematology have spoken out against the systematic search for aPLs in patients with COVID-19. In an attempt to bridge the gap on this hot topic, we conducted a comprehensive review of currently available cohort studies and case series systematically evaluating aPLs in COVID-19 patients. In this Perspective, we seek to identify both the frequency and the type of aPLs found in patients with COVID-19, as well as the potential association of these aPLs with vascular thrombosis and other distinctive characteristics of COVID-19. Furthermore, we investigated whether there is evidence that allows us to define the occurrence of aPLs in COVID-19 as an epiphenomenon, as has been observed in other systemic viral infections, or as antibodies against self-antigens bearing hallmarks that suggest a pathogenic role in immune-mediated thrombosis. Defining whether aPLs represent an epiphenomenon or they are actually involved in hemostatic abnormalities of COVID-19 is crucial both for uncovering novel mechanisms of immune-mediated thrombosis and for identifying potential prognostic biomarkers in this devastating disease.

Management of patients with antiphospholipid antibodies: what to do in laboratory scenarios that do not fit the guidelines

Introduction: Some patients with positive antiphospholipid antibodies (aPL) have not been included in randomized clinical trials or observational registries and, therefore, information on their risk of obstetric or thrombotic recurrence and optimal treatment is scarce.Areas covered: In the present review, the existing evidence regarding the management of two laboratory scenarios not covered by the guidelines is presented: (1) patients with antiphospholipid syndrome (APS) clinical manifestations and aPL positivity not fulfilling APS laboratory criteria, and (2) the possibility of discontinuing anticoagulation in APS patients whose aPL become persistently negative.Expert opinion: Growing evidence suggests a role for low titers and 'non-criteria' aPL, especially in obstetric APS. Treatment is not formally recommended but might be considered according to the individual's risk profile. Regarding the question of whether or not to discontinue anticoagulants after the 'spontaneous' disappearance of aPL, there is no definite answer. Retrospective studies seem to suggest that withdrawal of anticoagulation could be safe in certain patients with APS, especially in those with a first provoked venous thrombosis and whose aPL became persistently negative during follow-up. Still, before the withdrawal can be recommended in routine clinical practice, multicenter and prospective studies are required to validate this hypothesis.