Development of a certified reference material for anti-β2-glycoprotein I IgG - commutability studies

Objectives: In this paper, we describe the steps followed for the development of a certified reference material for immunoglobulin G antibodies against beta 2-glycoprotein I (also known as apolipoprotein H). These steps include processing of the material, commutability, the impact of dilution, the appropriate reconstitution conditions, homogeneity and stability during transport and storage. Methods: We analysed 69 clinical samples from patients suffering from antiphospholipid syndrome with several commercial enzyme-linked immunosorbent assays (ELISA) purchased from in vitro diagnostic manufacturers. Results: Analysis of the results indicated that the candidate reference material can be safely freeze-dried, and that the user should carefully follow the reconstitution instructions as small changes in e.g. temperature may have unwanted effects. The statistical analysis of the commutability studies indicated that the analytical response of the reference material upon dilution is similar to that of clinical samples, and that correlation between results may differ from assay to assay. Finally yet importantly, the presented and developed candidate reference material is commutable for most assays tested, homogeneous and stable. Conclusions: Immunoglobulin G antibodies against beta 2-glycoprotein I are associated with a higher risk of thrombosis and pregnancy complications. Their measurement is essential for the diagnosis and monitoring of antiphospholipid syndrome. These antibodies are detected by specific immunoassays, routinely used in clinical diagnostics, but various of these methods show enormous variability, in part due to the lack of a reference material.