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SAT0418 IGA Anti-Phosphatidylserin/Prothrombin Antibodies Present a Thrombotic Risk in Patients with Systemic Autoimmune Diseases
  1. P. Žigon,
  2. A. Ambrožič,
  3. M. Tomšič,
  4. S.S. Šemrl,
  5. S. Čučnik
  1. Department of Rheumatology, University Medical Centre, Ljubljana, Ljubljana, Slovenia


Background Studies on antiphospholipid antibodies (aPL) have mainly focused on the IgG and IgM isotypes, with only a few on the pathogenic significance of IgA aPL. Positive IgA anticardiolipin (aCL) and IgA anti-β2glycoprotein I (anti-β2GPI) were reported to be predominantly associated with other aPL, making it difficult to understand the role of IgA alone [1]. Recently, antibodies against phosphatidylserin/prothrombin (aPS/PT) IgG and IgM have been indicated as a potential marker for antiphospholipid syndrome (APS) [2, 3]. Our previous study reported that IgG and IgM aPS/PT showed highest association with lupus anticoagulant (LA) activity of all tested aPL [3], while no studies to date have investigated possible clinical benefits of IgA aPS/PT.

Objectives To determine the prevalence of IgA aPS/PT in patients with systemic autoimmune diseases and evaluate their association to thrombosis and obstetric complications.

Methods We examined 254 patients with systemic autoimmune diseases: 91 APS, 40 APS secondary to systemic lupus erythematosus (SLE), 47 SLE, 57 rheumatoid arthritis (RA) and 19 Sjögren's syndrome (SS) patients for LA, aCL, anti-β2GPI and aPS/PT (for IgG, IgM, IgA isotypes) [4]. 55 subjects experienced arterial thrombosis (AT), 60 venous thrombosis (VT) and 54 obstetric complications (OC).

Results An overall prevalence of 63/254 (25%) was found for IgA aPS/PT in our cohort of patients. IgA aPS/PT were statistically significantly associated to both AT and VT (p=0.026 and p=0.002, respectively), however no association was found to OC (p=0.534). 19/63 (30%) patients were solely positive for IgA aPS/PT and negative for IgG or IgM aPS/PT. Five of these patients (3 SLE, 1 RA and 1 SS) were concomitantly negative also for LA, aCL and anti-β2GPI. One of the solely positive IgA aPS/PT patients experienced AT, while the other four showed no clinical manifestations significant for APS. IgA aPS/PT showed significant association with LA activity (p<0.001; OR 4.7), comparable to IgG anti-β2GPI (OR 5.1) and higher than IgG/IgM aCL (OR<3.4) or IgM/IgA anti-β2GPI (OR<2.9).

Table 1

Conclusions IgA aPS/PT presented an independent risk factor for thrombosis, and highly correlated to LA activity. Larger studies are needed to confirm whether IgA aPS/PT testing could contribute to the assessment of thrombotic risk, especially in “seronegative” APS patients.


  1. Bertolaccini ML et. al., Autoimmunity reviews. 2014;13(9):917-30.

  2. Sciascia S, et al. Thrombosis and haemostasis. 2013;111(2).

  3. Zigon P, et al. Clinical and Developmental Immunology. 2013;2013:8.

  4. Zigon P, et al. Clin Chem Lab Med. 2011, 49:1011-1018

Disclosure of Interest None declared

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