title: Measuring IgA Anti-β2-Glycoprotein I and IgG/IgA Anti-Domain I Antibodies Adds Value to Current Serological Assays for the Antiphospholipid Syndrome.
abstract: BACKGROUND
  Currently available clinical assays to detect antiphospholipid antibodies (aPL) test for IgG and IgM antibodies to cardiolipin (aCL) and β2-glycoprotein I (aβ2GPI). It has been suggested that testing for IgA aPL and for antibodies to Domain I (DI), which carries the key antigenic epitopes of β2GPI, could add value to these current tests. We performed an observational, multicenter cohort study to evaluate the utility of IgG, IgM and IgA assays to each of CL, β2GPI and DI in APS.
  
  
  METHODS
  Serum from 230 patients with APS (n = 111), SLE but not APS (n = 119), and 200 healthy controls were tested for IgG, IgM and IgA aCL, aβ2GPI and aDI activity. Patients with APS were further classified into thrombotic or obstetric APS. Logistic regression and receiver operator characteristic analyses were employed to compare results from the nine different assays.
  
  
  RESULTS
  All assays displayed good specificity for APS; IgG aCL and IgG aβ2GPI assays however, had the highest sensitivity. Testing positive for IgA aβ2GPI resulted in a higher hazard ratio for APS compared to IgM aβ2GPI. Positive IgG, IgM or IgA aDI were all associated with APS, and in subjects positive for aCL and/or aβ2GPI, the presence of aDI raised the hazard ratio for APS by 3-5 fold. IgG aCL, aβ2GPI, aDI and IgA aDI were associated with thrombotic but not obstetric complications in patients with APS.
  
  
  CONCLUSIONS
  Measuring IgG aDI and IgA aβ2GPI and aDI may be useful in the management of patients with APS, particularly thrombotic APS.
authors.affiliation: Centre for Rheumatology Research, Division of Medicine, University College London, London, United Kingdom.
authors.forename: Charis
authors.initials: C
authors.lastname: Pericleous
authors.affiliation: Centre for Rheumatology Research, Division of Medicine, University College London, London, United Kingdom.
authors.forename: Isabel
authors.initials: I
authors.lastname: Ferreira
authors.affiliation: Laboratory of Immuno-rheumatology, IRCCS Istituto Auxologico Italiano, Milan, Italy.
authors.forename: Orietta
authors.initials: O
authors.lastname: Borghi
authors.affiliation: Laboratory of Immuno-rheumatology, IRCCS Istituto Auxologico Italiano, Milan, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Pregnolato
authors.affiliation: Centre for Rheumatology Research, Division of Medicine, University College London, London, United Kingdom.
authors.forename: Thomas
authors.initials: T
authors.lastname: McDonnell
authors.affiliation: Structural Biology, MRC National Institute for Medical Research, London, United Kingdom.
authors.forename: Acely
authors.initials: A
authors.lastname: Garza-Garcia
authors.affiliation: Structural Biology, MRC National Institute for Medical Research, London, United Kingdom.
authors.forename: Paul
authors.initials: P
authors.lastname: Driscoll
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, University of Texas Medical Branch, Galveston, Texas, United States of America.
authors.forename: Silvia
authors.initials: S
authors.lastname: Pierangeli
authors.affiliation: Centre for Rheumatology Research, Division of Medicine, University College London, London, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Isenberg
authors.affiliation: Centre for Rheumatology Research, Division of Medicine, University College London, London, United Kingdom.|Arthritis Research UK Centre for Adolescent Rheumatology, UCL Hospital and Great Ormond Street Hospital, London, United Kingdom.
authors.forename: Yiannis
authors.initials: Y
authors.lastname: Ioannou
authors.affiliation: Centre for Rheumatology Research, Division of Medicine, University College London, London, United Kingdom.
authors.forename: Ian
authors.initials: I
authors.lastname: Giles
authors.affiliation: Laboratory of Immuno-rheumatology, IRCCS Istituto Auxologico Italiano, Milan, Italy.
authors.forename: Pier Luigi
authors.initials: PL
authors.lastname: Meroni
authors.affiliation: Centre for Rheumatology Research, Division of Medicine, University College London, London, United Kingdom.
authors.forename: Anisur
authors.initials: A
authors.lastname: Rahman
mesh_terms: D000328:Adult; D017153:Antibodies, Anticardiolipin / Q000097:blood*; D017152:Antibodies, Antiphospholipid / Q000276:immunology / Q000302:isolation & purification*; D016736:Antiphospholipid Syndrome / Q000097:blood* / Q000276:immunology / Q000473:pathology; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D005260:Female; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D012698:Serologic Tests; D013927:Thrombosis / Q000097:blood* / Q000276:immunology; D053482:beta 2-Glycoprotein I / Q000276:immunology / Q000302:isolation & purification*
chemical_list: D017153:Antibodies, Anticardiolipin; D017152:Antibodies, Antiphospholipid; D000939:Epitopes; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D053482:beta 2-Glycoprotein I