title: Prevalence and significance of anti-prothrombin (aPT) antibodies in patients with Lupus Anticoagulant (LA).
abstract: OBJECTIVE
  Anti-prothrombin (aPT) antibodies have been found in Lupus Anticoagulant (LA) positive patients. Their prevalence and relative contribution to thromboembolic risk in LA-positive patients is not well defined. The aim of this study was to determine their presence and association with thromboembolic events in a large series of patients with confirmed LA.
  
  
  METHODS
  Plasma from LA-positive patients was collected at Thrombosis Centers and sent to a reference central laboratory for confirmation. Positive plasma was tested using home-made ELISA for the presence of aPT and anti-beta(2)GPI antibodies.
  
  
  RESULTS
  LA was confirmed in 231 patients. Sixty-one of 231 (26%, 95%CI 22-33) LA positive subjects were positive for IgG aPT and 62 (27%, 95% CI 21-33) were positive for IgM aPT antibodies. Clinical features of Antiphospholipid Syndrome (APS) were not associated with the presence of IgG aPT [43 APS in 61 (70%) positive and 109 APS in 170 (64%) negative IgG aPT subjects, p=ns] or IgM aPT. Rate of positivity of IgG and IgM a beta(2)GPI was significantly higher than that of IgG and IgM aPT. Clinical events accounting for APS occurred in 97 of 130 (75%) IgG a beta(2)GPI positive and in 55 of 101 (54%) IgG a beta(2)GPI negative patients (OR 2.4, 95% CI 1.4 to 4.3, p=0.002). No significant association with clinical events in patients positive for both IgG aPT and IgG a beta(2)GPI as compared to those positive for one or another test was found. When patients negative for both IgG aPT and IgG a beta(2)GPI (LA positive only) were compared with remaining patients, a significantly lower association with clinical events was found (OR=0.4, 95% CI: 0.2 to 0.7, p=0.004).
  
  
  CONCLUSIONS
  As compared to IgG a beta(2)GPI, the prevalence of IgG aPT in patients with LA is significantly lower and not associated with the clinical features of APS.
authors.affiliation: Clinical Cardiology, Thrombosis Centre, University Hospital, Padova. vittorio.pengo@unipd.it
authors.forename: V
authors.initials: V
authors.lastname: Pengo
authors.forename: G
authors.initials: G
authors.lastname: Denas
authors.forename: E
authors.initials: E
authors.lastname: Bison
authors.forename: A
authors.initials: A
authors.lastname: Banzato
authors.forename: S Padayattil
authors.initials: SP
authors.lastname: Jose
authors.forename: P
authors.initials: P
authors.lastname: Gresele
authors.forename: F
authors.initials: F
authors.lastname: Marongiu
authors.forename: N
authors.initials: N
authors.lastname: Erba
authors.forename: F
authors.initials: F
authors.lastname: Veschi
authors.forename: A
authors.initials: A
authors.lastname: Ghirarduzzi
authors.forename: E
authors.initials: E
authors.lastname: De Candia
authors.forename: B
authors.initials: B
authors.lastname: Montaruli
authors.forename: M
authors.initials: M
authors.lastname: Marietta
authors.forename: S
authors.initials: S
authors.lastname: Testa
authors.forename: D
authors.initials: D
authors.lastname: Barcellona
authors.forename: A
authors.initials: A
authors.lastname: Tripodi
mesh_terms: D000328:Adult; D000906:Antibodies / Q000097:blood / Q000276:immunology*; D016736:Antiphospholipid Syndrome / Q000097:blood / Q000276:immunology*; D005260:Female; D006801:Humans; D016682:Lupus Coagulation Inhibitor / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011516:Prothrombin / Q000276:immunology*; D053482:beta 2-Glycoprotein I / Q000276:immunology*
chemical_list: D000906:Antibodies; D016682:Lupus Coagulation Inhibitor; D053482:beta 2-Glycoprotein I; D011516:Prothrombin