Inter-laboratory Variability of Anti-β2-glycoprotein I Measurement

Guido Reber; Inger Schousboe; Angela Tincani; Marielle Sanmarco; Tanja Kveder; Philippe de Moerloose; Marie-Claire Boffa; Josiane Arvieux

doi:10.1055/s-0037-1613156

Thrombosis and Haemostasis, Table of Contents

Thromb Haemost 2002; 88(01): 66-73
DOI: 10.1055/s-0037-1613156

Review Article

Schattauer GmbH

Inter-laboratory Variability of Anti-β₂-glycoprotein I Measurement

A Collaborative Study in the Frame of the European Forum on Antiphospholipid Antibodies Standardization Group

Guido Reber

¹Haemostasis Unit, Geneva University Hospital, Switzerland

,

Inger Schousboe

²The Panum Institute, Copenhagen, Denmark

,

Angela Tincani

³Clinical Immunology Unit, Brescia Hospital, Italy

,

Marielle Sanmarco

⁴Laboratoire d’Immunologie, Hôpital de la Conception, Marseille, France

,

Tanja Kveder

⁵University Medical Center, Ljubljana, Slovenia

,

Philippe de Moerloose

¹Haemostasis Unit, Geneva University Hospital, Switzerland

,

Marie-Claire Boffa

⁶Department of Internal Medicine JC Piette, Hôpital de la Pitié, Paris, France

,

Josiane Arvieux

⁷Laboratoire d’Immunologie, CHU de Brest, France

› Author Affiliations

Abstract

Summary

Inter-laboratory variability of anti-β₂-glycoprotein I antibody measurements (IgG and IgM) was investigated in the frame of the European Forum on Antiphospholipid Antibodies and its Standardization Group. Twenty-eight samples from patients with autoimmune diseases, two samples from blood donors and a set of six calibrators obtained by dilution with normal plasma of a pool of patient samples were sent to 21 European centers. Six of them used commercial kits and the others home-made assays. Marked differences in the steepness of the calibration curves obtained with the calibrator provided were observed. The standard deviations of sample measurement were high. Cut-off of positivity varied from 7 to 90 Forum Units (FU) for IgG and from 10 to 138 FU for IgM, whereas the rate of positivity varied from 50 to 93% for IgG and from 13 to 70% for IgM. No clear relationship between cut-off values and positivity rate could be established for either isotype. Adopting a common cut-off did not markedly improve the overall agreement between centers in positive/negative sample classification. Because of the majority of low positive samples, excellent concordance between centers (as defined by kappa values from 0.8 and 1) occurred only in 13% of cases for IgG and in 6% of cases for IgM, because many selected samples were low-positive. Despite the large variability of anti-β₂-glycoprotein I measurements between centers, the agreement on results with highand medium-positive samples was good.

Keywords

Anti-β₂-glycoprotein I antibodies - assays - standardization

Full Text

References

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