Risk Assessment and Antithrombotic Strategies in Antiphospholipid Antibody Carriers

Anti-phospholipid autoantibodies in human diseases

Anti-phospholipid autoantibodies are a group of antibodies that can specifically bind to anionic phospholipids and phospholipid protein complexes. Recent studies have reported elevated serum anti-phospholipid autoantibody levels in patients with antiphospholipid syndrome, systemic lupus erythematosus, rheumatoid arthritis, metabolic disorders, malaria, SARS-CoV-2 infection, obstetric diseases and cardiovascular diseases. However, the underlying mechanisms of anti-phospholipid autoantibodies in disease pathogenesis remain largely unclear. Emerging evidence indicate that anti-phospholipid autoantibodies modulate NETs formation, monocyte activation, blockade of apoptotic cell phagocytosis in macrophages, complement activation, dendritic cell activation and vascular endothelial cell activation. Herein, we provide an update on recent advances in elucidating the effector mechanisms of anti-phospholipid autoantibodies in the pathogenesis of various diseases, which may facilitate the development of potential therapeutic targets for the treatment of anti-phospholipid autoantibody-related disorders.

Added value of antiphosphatidylserine/prothrombin antibodies in the workup of thrombotic antiphospholipid syndrome: Communication from the ISTH SSC Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibodies

BACKGROUND

Diagnosis of antiphospholipid syndrome (APS) requires persistent presence of lupus anticoagulant (LAC), anticardiolipin (aCL) IgG/IgM, or anti-β2 glycoprotein I (aβ2GPI) IgG/IgM antibodies. Other antiphospholipid antibodies (aPL) such as antiphosphatidylserine/prothrombin antibodies (aPS/PT) are promising in assessment of thrombotic APS (TAPS).

AIM

To evaluate the added value of aPS/PT IgG and IgM in TAPS.

MATERIAL AND METHODS

aPS/PT IgG/IgM, aCL IgG/IgM, aβ2GPI IgG/IgM, and LAC were determined in 757 patients (TAPS and controls). aPS/PT cut-off values were calculated, and aPS/PT titers and positivity were compared between TAPS and controls, type of thrombosis, and antibody profiles. Likelihood ratios (LR), odds ratios (OR), and aPL score were determined.

RESULTS

aPS/PT IgG and IgM were associated with TAPS and triple positivity. In-house calculated cut-offs were higher for IgM (43 units), compared to manufacturer's cut-off (30 units). Thresholds of 90 (IgG) and 200 (IgM) units were determined as high-titer cut-off. Higher aPS/PT titers were observed in triple positive patients and showed higher LR and OR for TAPS. aPS/PT was independently associated with TAPS when adjusted for aCL/aβ2GPI, but not when adjusted for LAC. In isolated LAC positive patients, aPS/PT was positive in 27.1% TAPS patients and in 77.3% patients with autoimmune disease. Diagnostic value of aPL score did not differ with and without including aPS/PT.

CONCLUSION

aPS/PT positivity, especially with high antibody titer, is associated with TAPS diagnosis. Analysis on top of current laboratory criteria is not essential in TAPS diagnosis, but aPS/PT could be useful in patients with thrombosis and a double positive aPL profile (aCL+/aβ2GPI+).

Antiphospholipid antibodies in the obstetric antiphospholipid syndrome: Detection and antibodies profile at the Maternity and Neonatal Medicine Center of Monastir, Tunisia

PURPOSE

This study aimed to implement lupus anticoagulant (LAC) detection techniques according to the International Society on Thrombosis and Hemostasis (ISTH) recommendations, in the Biological Laboratory of the Maternity and Neonatal Medicine Center (Monastir, Tunisia) and to evaluate the profile and the prevalence of antiphospholipid antibodies (aPL) in the obstetric antiphospholipid syndrome (OAPS).

METHODS

We collected two groups: a "case group" (53 women who presented one or more obstetrical criteria of APS) and a "control group." LAC was detected following the four steps recommended by ISTH 2009. Anticardiolipin (aCL) and antibeta-2-glycoprotein I (aβ2GPI) antibodies testing were performed by enzyme-linked immunosorbent assay (ELISA).

RESULTS

aPL were found in five patients: three patients with isolated LAC, one patient with isolated IgG aCL, and one patient with triple positivity (LAC, aCL IgM, aβ2GPI IgM). Concerning LAC, 13 (24.52%) of 53 patients had a screening step with at least one positive test. The mixing step was positive in four patients and then confirmed in the confirmatory test. Thus, the prevalence of LAC in our study group is 7.54%. Surprisingly, among these positive patients, one patient had an associated combined factor V (FV) and factor VIII (FVIII) deficiency.

CONCLUSION

There is no single test and no algorithm that can detect all types of LAC. It seems that the recent 2020 ISTH algorithm allows a better detection of low activity LAC than the 2009 algorithm. In our study, the most frequently identified antiphospholipid antibodies were LAC more than aCL and aβ2GPI.

Detection of IgA Antiphospholipid Antibodies Does not Improve Thrombotic Antiphospholipid Syndrome Classification: A two-Center Study

Background

Thrombotic antiphospholipid syndrome (APS) is a systemic autoimmune disease; its diagnosis requires meeting both clinical and laboratory criteria. Prevalence rates of immunoglobulin (Ig) A anticardiolipin antibodies (aCL) and IgA anti-β₂ glycoprotein I antibodies (aβ₂GPI) remain unknown, and the clinical value of these antibodies to APS classification remains controversial. Therefore, we aimed to examine both items in the Chinese population.

Methods

Using chemiluminescence immunoassay, antiphospholipid antibodies (aPL) were quantified in 12,582 hospital-based general population, 278 thrombotic APS patients, and 233 healthy controls.

Results

In the general population, the positive rates of IgA aCL and IgA aβ₂GPI antibodies were 2.87% and 1.99%, respectively. Furthermore, isolated IgA aPL-positivity rate was 0.72% in patients with APS, which was comparable to those in the general population (0.68%, p = 1) and in healthy controls (0.43%, p = 1). Among the IgA aPL-positive individuals in the general population, isolated IgA-positive individuals had lower serum levels of IgA antibodies (p = 0.007 for IgA aCL and p = 0.059 for IgA aβ₂GPI). Regarding to APS classification, adding IgA aPL into conventional aPL assays may not improve and may even deteriorate the net reclassification index for APS; besides, no association between thrombosis and IgA aPL was observed.

Conclusions

this study assessed the prevalence of various aPL in Chinese population. IgA aPL may not enhance the classification ability of established laboratory criteria for thrombotic APS. Our data do not support the addition of IgA aPL to conventional aPL assays.

Anti-Phospholipid Antibodies and COVID-19 Thrombosis: A Co-Star, Not a Supporting Actor

Background: COVID-19 clinical features include a hypercoagulable state that resembles the antiphospholipid syndrome (APS), a disease characterized by thrombosis and presence of antiphospholipid antibodies (aPL). The relationship between aPL-presence and the appearance of thrombi as well as the transience or permanence of aPL in COVID-19 patients is not sufficiently clear. Methods: A group of 360 COVID-19 patients were followed-up for 6 months. Classic aPL, anti-B2GPI IgA, anti-phosphatidylserine/prothrombin IgG/M and anti-SARS-CoV-2 antibodies were determined at acute phase and >12 weeks later. The reference group included 143 healthy volunteers of the same age-range distribution. Results: aPL prevalence was similar in COVID-19 patients and the reference population. aPL presence in both determinations was significantly associated with thrombosis (OR: 2.33 and 3.71), strong agreement being found for classic aPL and anti-B2GPI IgA (Weighted kappa: 0.85–0.91). Thrombosis-associated aPL occurred a median of 17 days after hospital admission (IQR: 6–28) vs. 4 days for the rest (IQR: 3–7). Although anti-SARS-CoV-2 antibodies levels increased during convalescence, aPL hardly changed. Conclusions: Most COVID-19 patients would carry these aPL before the infection. At least two mechanisms could be behind thrombosis, early immune-dysregulation-mediated thrombosis after infection and belated-aPL-mediated thrombosis, with SARS-CoV-2 behaving as a second hit.