title: Antibodies to Domain 4/5 (Dm4/5) of β2-Glycoprotein 1 (β2GP1) in different antiphospholipid (aPL) antibody profiles.
abstract: BACKGROUND
  Determination of the three recommended tests for the diagnosis of antiphospholipid syndrome [Lupus Anticoagulant (LA), anticardiolipin (aCL) and anti β2-Glycoprotein 1 (aβ2GP1) antibodies] allow physicians to allocate patients into classification (risk) categories.
  
  
  OBJECTIVE
  To measure antibodies of IgG isotype directed towards Domain 4/5 (Dm4/5) of β2GP1.
  
  
  METHODS
  In this cross-sectional study we measured IgG aβ2GP1-Dm4/5 in a group of individuals positive for IgG aβ2GP1 and classified as triple (LAC+, IgG aCL+, IgG aβ2GP1+, n=32), double (LAC-, IgG aCL+, IgG aβ2GP1+, n=23) or single positive (LA-, IgG aCL-, IgG aβ2GP1+, n=10).
  
  
  RESULTS
  Geometric mean and standard deviation of IgG aβ2GP1 values expressed as Chemiluminescent Units (CU) in triple, double, single positive groups and in 40 healthy individuals were 1795±783, 321±181, 29±8 and 5.0±1.0, respectively (ANOVA p<0.0001). Geometric mean and standard deviation of IgG aβ2GP1-Dm4/5 expressed as Optical Density (OD) in triple, double and single positive groups and in 40 healthy individuals were 0.16±0.13, 0.16±0.15 and 0.26±0.15, 0.13±0,11, respectively (ANOVA p<0.002). Individuals in the single positive group, expressed significantly higher values with respect to triple (p=0.04) and double (p=0.03) positive groups. Approximate OD cut-off value (99° percentile) calculated in 40 normal control subjects is 0.404. Positivity to IgG aβ2GP1-Dm4/5 according to this cutoff was found in only 5 individuals, 3 in triple positive and 2 in single positive groups and was not associated with thromboembolism.
  
  
  CONCLUSIONS
  Mean level of IgG aβ2GP1-Dm4/5 is higher in single positive group. There is no association between positivity to IgG aβ2GP1-Dm4/5 and thromboembolic events.
authors.affiliation: Clinical Cardiology, Thrombosis Centre, Department of Cardiac Thoracic and Vascular Sciences, University of Padua, Padua, Italy; Rheumatology Unit, Department of Medicine, University of Padua, Padua, Italy. Electronic address: vittorio.pengo@unipd.it.
authors.forename: V
authors.initials: V
authors.lastname: Pengo
authors.affiliation: Clinical Cardiology, Thrombosis Centre, Department of Cardiac Thoracic and Vascular Sciences, University of Padua, Padua, Italy; Rheumatology Unit, Department of Medicine, University of Padua, Padua, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Ruffatti
authors.affiliation: Clinical Cardiology, Thrombosis Centre, Department of Cardiac Thoracic and Vascular Sciences, University of Padua, Padua, Italy; Rheumatology Unit, Department of Medicine, University of Padua, Padua, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Tonello
authors.affiliation: Clinical Cardiology, Thrombosis Centre, Department of Cardiac Thoracic and Vascular Sciences, University of Padua, Padua, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Hoxha
authors.affiliation: Clinical Cardiology, Thrombosis Centre, Department of Cardiac Thoracic and Vascular Sciences, University of Padua, Padua, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Bison
authors.affiliation: Clinical Cardiology, Thrombosis Centre, Department of Cardiac Thoracic and Vascular Sciences, University of Padua, Padua, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Denas
authors.affiliation: Clinical Cardiology, Thrombosis Centre, Department of Cardiac Thoracic and Vascular Sciences, University of Padua, Padua, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Padayattil Jose
authors.affiliation: Clinical Cardiology, Thrombosis Centre, Department of Cardiac Thoracic and Vascular Sciences, University of Padua, Padua, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Zoppellaro
authors.affiliation: Clinical Cardiology, Thrombosis Centre, Department of Cardiac Thoracic and Vascular Sciences, University of Padua, Padua, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Bracco
authors.affiliation: Clinical Cardiology, Thrombosis Centre, Department of Cardiac Thoracic and Vascular Sciences, University of Padua, Padua, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Banzato
mesh_terms: D017152:Antibodies, Antiphospholipid / Q000097:blood / Q000276:immunology*; D016736:Antiphospholipid Syndrome / Q000097:blood / Q000276:immunology*; D003430:Cross-Sectional Studies; D000939:Epitopes / Q000737:chemistry / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology*; D017434:Protein Structure, Tertiary; D053482:beta 2-Glycoprotein I / Q000737:chemistry / Q000276:immunology*
chemical_list: D017152:Antibodies, Antiphospholipid; D000939:Epitopes; D007074:Immunoglobulin G; D053482:beta 2-Glycoprotein I
keywords: Antibodies; Antiphospholipid syndrome; Epitopes; Glycoproteins; Thrombosis