Optimising testing for phospholipid antibodies

Abstract

Aim: To compare anticardiolipin (ACL) and anti-beta2 glycoprotein 1 (beta2gp1) 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 beta2gp1 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-beta2gp1 assay in the diagnosis of APS. Meta-analysis confirmed that neither assay is perfect, although the anti-beta2gp1 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-beta2gp1 assay is exploited where infection, connective tissue disease, or atheroma are present.

Figure 1 Receiver operating characteristic curves for anticardiolipin (ALC) and anti-ß2 glycoprotein 1 (anti-ß2gp1) assays. Assays are: (A) non-quantitative total ACL, (B) quantitative total ACL, (C) IgG ACL, (D) IgM ACL, (E) IgG anti-ß2gp1, (F) IgM anti-ß2gp1.

Figure 2 Sensitivities (A) and specificities (B) for anticardiolipin (ACL) and anti-ß2 glycoprotein 1 (anti-ß2gp1) assays in individual reports and derived from pooled data.