Optimising testing for phospholipid antibodies

Aim-To compare anticardiolipin (ACL) and anti-beta2 glycoprotein 1 (beta 2gp1) enzyme linked immunosorbent assays (ELISAs) in the diagnosis of antiphospholipid syndrome (APS) and to incorporate these results into a meta-analysis of published data. Method-Three representative commercial ACL ELISAs and an in house beta 2gp1 assay were optimised and then assessed on 124 sera from normal donors, patients with infection, or patients with APS. A Medline search was screened for papers meeting defined criteria to conduct a meta-analysis. The performance of the assays used in this study was included. Results-A non-quantitative ACL assay performed at least as well as the anti-beta 2gp1 assay in the diagnosis of APS. Meta-analysis confirmed that neither assay is perfect, although the anti-beta 2gp1 assay had a higher specificity and lower sensitivity than the ACL assay. Conclusions-The pooled data suggest that the ACL assay is used to investigate thrombosis without overt underlying pathology and that the improved specificity of the anti-beta 2gp1 assay is exploited where infection, connective tissue disease, or atheroma are present.