Evaluation of the Different Antiphospholipid Antibodies for the Diagnosis of Antiphospholipid Syndrome

Objective: Antiphospholipid syndrome (APS) or Hughes syndrome is a frequently seen condition in Kuwait that is characterised by the presence of significant titres of a variety of antiphospholipid antibodies (aPL). The main clinical features of this syndrome include thrombosis (both venous and arterial), recurrent fetal wastage and thrombocytopenia. The aim of the present study was to find out the antibodies with a high predictive value for the diagnosis of APS. Methodology: The study included a total of 38 subjects. Nine of them were patients with proven primary APS, 10 with secondary APS and 19 were patients (controls) with weak clinical evidence of APS. After a complete clinical examination and routine investigations, the following categories of aPL were estimated by standard laboratory techniques: anticardiolipin antibodies of IgG and IgM isotypes (GPL and MPL, respectively), anti-β2-glycoprotein-I antibodies (anti-β2-GPI) of IgG and IgM isotypes and activated partial thromboplastin time as a surrogate for lupus anticoagulant (LAC). The tests were considered positive if the titres were more than a standard cut-off value provided by the manufacturer of the kits, and in one instance, the normal range was established in our laboratory (LAC). Results: The highest sensitivity (78.9%) and diagnostic accuracy (71.1%) were obtained by the estimation of GPL. However, excellent specificity (100%) and positive predictive value (100%) with almost as good a diagnostic accuracy (68.4%) were also obtained with anti-β2-GPI of IgG isotype. All the other tests performed poorly when compared with these two. There was no difference in the performance of these tests between primary and secondary APS. Conclusion: Of the various aPL estimated, GPL and anti-β2-GPI of IgG isotype were statistically sensitive and specific investigations for confirming the diagnosis of APS.