Research report
Measurement of anti-phospholipid antibodies by ELISA using β2-glycoprotein I as an antigen

https://doi.org/10.1016/0022-1759(91)90047-JGet rights and content

Abstract

The requirement of plasma cofactor β2-glycoprotein I for binding autoantibodies against anionic phospholipids has been reported. We describe the development of an enzyme-linked immunosorbent assay (ELISA) for anti-phospholipid antibodies using highly purified β2-glycoprotein I for coating microtitre plates. Intra- and interassay coefficients of variation, determined with serum pools of low, medium and high positivity, ranged between 3% and 18%. 54 sera from patients with systemic lupus erythematosus and related autoimmune disorders were analyzed by this assay; the results correlated well to those obtained in an ELISA using anionic phospholipids on the solid phase (r = 0.85, P < 0.001). The two ELISA systems showed similar sensitivities although 831 positive sera scored negative in the β2-glycoprotein I ELISA. The latter group of eight sera showed significantly higher anti-phosphatidylcholine/anti-phosphatidylserine binding ratios than the group of 23 sera which scored positive in both assays. This new assay should permit accurate measurement of most of the clinically relevant anti-phospholipid antibodies and avoid inconsistencies likely to arise from secondary interactions that characterize lipid-based ELISA.

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