title: International standards for IgG and IgM anti-β2glycoprotein antibody measurement.
abstract: International standards for anti-beta2 glycoprotein I (anti-β2GPI) testing are needed. We evaluated the suitability of polyclonal/monoclonal candidate reference materials (RM) for the assay. IgG/IgM anti-β2GPI were affinity-purified (AP) from high-positive antiphospholipid syndrome sera and IgG from HCAL clone supernatant. Igs were tested for purity by SDS-PAGE, pooled, concentrated, sterile-filtered and the protein concentration determined. One unit was defined as the binding activity of 1 µg/ml of AP anti-β2GPI Ig. IgG/IgM RM were each assigned a unit value using the respective AP material as a calibrator. Polyclonal/monoclonal RM and 30 samples were evaluated for linearity, unit equivalency and commutability. Polyclonal AP material was assigned a value of 100 U IgG and 15 U IgM anti-β2GPI, respectively. IgG-RM had a value of 270 IgG and the IgM-RM of 220.3 IgM anti-β2GPI U. The linearity (R (2)) of each RM curve for the various assays ranged from 0.96 to 0.99. Commutability samples fit very well within 95% prediction intervals and had excellent correlation when comparing assays. IgG and IgM polyclonal and IgG monoclonal RM displayed excellent linearity and commutability, being good candidates for better standardization of anti-β2GPI immunoassays.
authors.affiliation: Rheumatology and Internal Medicine, University of Texas Medical Branch, Galveston, TX, USA pierluigi.meroni@unimi.it.
authors.forename: R
authors.initials: R
authors.lastname: Willis
authors.affiliation: Experimental Laboratory of Immunological and Rheumatologic Researches, IRCCS Istituto Auxologico Italiano, Milan, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Grossi
authors.affiliation: Experimental Laboratory of Immunological and Rheumatologic Researches, IRCCS Istituto Auxologico Italiano, Milan, Italy Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Orietta Borghi
authors.affiliation: European Commission Joint Research Centre, Institute for Reference Materials and Measurements (IRMM), Geel, Belgium.
authors.forename: G
authors.initials: G
authors.lastname: Martos-Sevilla
authors.affiliation: European Commission Joint Research Centre, Institute for Reference Materials and Measurements (IRMM), Geel, Belgium.
authors.forename: I
authors.initials: I
authors.lastname: Zegers
authors.affiliation: Protein Reference Unit, St George's Hospital, London, UK.
authors.forename: J
authors.initials: J
authors.lastname: Sheldon
authors.affiliation: Experimental Laboratory of Immunological and Rheumatologic Researches, IRCCS Istituto Auxologico Italiano, Milan, Italy Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy.
authors.forename: P L
authors.initials: PL
authors.lastname: Meroni
mesh_terms: D001323:Autoantibodies / Q000097:blood*; D006801:Humans; D007118:Immunoassay / Q000592:standards; D007074:Immunoglobulin G / Q000097:blood*; D007075:Immunoglobulin M / Q000097:blood*; D012015:Reference Standards; D053482:beta 2-Glycoprotein I / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D053482:beta 2-Glycoprotein I
keywords: Anti-β2glycoprotein I antibodies; reference materials; standardization