title: Anti-beta2-glycoprotein I ELISA: methodology, determination of cut-off values in 434 healthy Caucasians and evaluation of monoclonal antibodies as possible international standards.
abstract: Antibodies against beta2-glycoprotein I are among the most commonly detected subset of antiphospholipid antibodies. The inter-laboratory comparability of results is hardly possible due to methodological differences, lack of international standards and different cut-off values. We evaluated an ELISA for the detection of anti-beta2-glycoprotein I using the analytical goals based on biological variations for similar analytes (immunoglobulins). By our ELISA we fulfilled the optimal (IgA, IgM) or minimal (IgG) analytical goals in long-term imprecision. The determination of cut-off values was based on the frequency distribution of results obtained on 434 healthy Caucasians. To aim at a better inter-laboratory comparability we tested two monoclonal antibodies as possible calibrators: HCAL (IgG) and EY2C9 (IgM). Binding properties determined by dilutional curves showed great similarities with polyclonal sera, used as in-house standards. Cut-off values were expressed by concentrations of IgG and IgM monoclonal antibodies (4.5 and 25.3 microg/l). Our study shows the possibility for a successful application of analytical goals based on biological variation even when data for a particular analyte are not available. The expression of cut-off values, obtained on a large scale Caucasian population, by the concentration of IgG and IgM monoclonal antibodies could make possible a more reliable inter-laboratory comparison of data.
authors.affiliation: University Medical Centre, Department of Rheumatology, Ljubljana, Slovenia.
authors.forename: S
authors.initials: S
authors.lastname: Cucnik
authors.forename: A
authors.initials: A
authors.lastname: Ambrozic
authors.forename: B
authors.initials: B
authors.lastname: Bozic
authors.forename: M
authors.initials: M
authors.lastname: Skitek
authors.forename: T
authors.initials: T
authors.lastname: Kveder
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000276:immunology*; D002138:Calibration; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods* / Q000592:standards*; D005260:Female; D005780:Gelatin; D006023:Glycoproteins / Q000032:analysis / Q000276:immunology*; D006801:Humans; D007106:Immune Sera / Q000276:immunology; D007070:Immunoglobulin A / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D008297:Male; D008875:Middle Aged; D012015:Reference Standards; D015203:Reproducibility of Results; D012709:Serum Albumin; D044465:White People; D053482:beta 2-Glycoprotein I
chemical_list: D000911:Antibodies, Monoclonal; D006023:Glycoproteins; D007106:Immune Sera; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D012709:Serum Albumin; D053482:beta 2-Glycoprotein I; D005780:Gelatin