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THU0039 Relationship between Antiphosphatidylserine/Prothrombin Antibodies and Conventional Antiphospholipid Antibodies in Primary Antiphospholipid Syndrome
  1. A. Hoxha,
  2. A. Calligaro,
  3. M. Favaro,
  4. E. Mattia,
  5. L. Meneghel,
  6. M. Tonello,
  7. M. Facchinetti,
  8. A. Ruffatti,
  9. L. Punzi
  1. Department of Medicine, University of Padua, Padua, Italy


Background There is a large consensus regarding the association with APS clinical features of antiprothrombin antibodies, directed to phosphatidylserine/prothrombin complex.

Objectives As their diagnostic value remain matter to debate we designed a study to evaluate the prevalence of anti-phosphatidylserine/prothrombin (aPS/PT) in primary APS (PAPS) and their association with the conventional aPL.

Methods Plasma and serum samples were collected from 160 PAPS patients (137 females and 23 males, mean age = 44 years ±11.8 SD ranging between 18 and 77) attending Rheumatology Unit of Padua University. IgG/IgM aPS/PT antibodies were detected using commercial ELISA kits, kindly provided by INOVA Diagnostics, Inc. (San Diego, California, USA), following the manufacturer's instructions. IgG/IgM aCL and IgG/IgM antiβ2GPI antibodies were measured using “home-made” ELISA kits. LA was detected according to internationally accepted guidelines.

Results IgG aPS/PT antibodies alone were positive in 12 (7.5%), IgM alone in 41 (25.6%), and both IgG and IgM isotypes in 36 (22.5%) of PAPS patients. IgG aPS/PT antibodies were significantly associated with IgG aCL, IgG antiβ2GPI and LA (OR 11.8, 95% CI 4.7-29.5; OR 6, 95% CI 2.8-12.9 and OR 14.1, 95% CI 6.1-32; respectively). Instead, IgM aPS/PT antibodies were significantly associated only with LA (OR 6.9, 95% CI 3.7-12.9). The mean titres of IgG aPS/PT were significantly higher in IgG aCL positive (aCL+ve) vs IgG aCL negative (aCL-ve) in IgG antiβ2GPI positive (antiβ2GPI+ve) vs IgG antiβ2GPI negative (antiβ2GPI–ve) and in LA positive (LA+ve) vs LA negative (LA-ve) patients (p<0.0001 for all associations). The mean titres of IgM aPS/PT were significantly higher in IgM aCL+ve vs IgM aCL-ve in IgM antiβ2GPI+ve vs IgM antiβ2GPI-ve and in LA+ve vs LA-ve patients (p=0.02, p=0.02 and p<0.0001, respectively). Moreover, there was a significant correlation between IgG aPS/PT levels and IgG aCL, IgG antiβ2GPI levels and the presence of LA (rho=0.42, p<0.0001; rho=0.4, p<0.0001 and rho=0.5, p<0.0001, respectively). While IgM aPS/PT significantly correlate only with the presence of LA (rho=0.44, p<0.0001). We compare the prevalence of IgG and IgM aPS/PT antibodies in the different conventional aPL antibodies profile (triple vs double vs single aPL positivity). IgG aPS/PT is significantly frequent in triple than in double and in triple than in single positivity (OR 11, 95% CI 5.3-22.7; OR 19.9, 95% CI 8.4-47.4; respectively), but not in double vs single positivity. Even, IgM aPS/PT is significantly frequent in triple than in double and in triple than in single positivity (OR 5.8, 95% CI 3.2-10.9; OR 10, 95% CI 5.2-19.2, respectively), but not in double vs single positivity. Moreover, both IgG and IgM aPS/PT antibodies mean titres were significantly higher in triple aPL positivity than in triple aPL negative patients (p<0.0001 for both).

Conclusions As there was no correlation between IgM aPS/PT and IgM aCL and IgM antiβ2GPI, they might be considered a diagnostic tool for PAPS.

Disclosure of Interest : None declared

DOI 10.1136/annrheumdis-2014-eular.5799

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