Optimising testing for phospholipid antibodies

Aim—To compare anticardiolipin (ACL) and anti-s2 glycoprotein 1 (s2gp1) 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 s2gp1 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-s2gp1 assay in the diagnosis of APS. Meta-analysis confirmed that neither assay is perfect, although the anti-s2gp1 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-s2gp1 assay is exploited where infection, connective tissue disease, or atheroma are present. Key Words: antiphospholipid syndrome • anticardiolipin antibodies • anti-s2 glycoprotein 1 • sensitivity