Revised classification criteria for antiphospholipid syndrome and the thrombotic risk in patients with autoimmune diseases.

Summary. Background: The classification criteria for antiphospholipid syndrome (APS) were updated in 2006. Objective: The aim of the study was to analyze associations between clinical complications and laboratory test abnormalities typical for APS in a group of patients with autoimmune diseases, based on the recently updated criteria. Patients/methods: Three hundred and thirty-six patients were enrolled into the study, with the majority (n = 235) suffering from systemic lupus erythematosus. Laboratory determinations included: lupus anticoagulant (LA), anticardiolipin (aCL) and anti-beta2-glycoprotein I (anti-β2GPI) antibodies (ABs) [of both immunoglobulin G (IgG) and IgM class]. Results: A significant association was found between laboratory and clinical features of APS; odds ratios (ORs) for thrombosis associated with the presence of LA, aCL, and anti-β2GPI Abs were 4.04 [95% CI: 2.44–6.68], 3.71 (95% CI 2.32–5.92) and 2.57 (95% CI 1.60–4.1), respectively. Detailed analysis showed marked differences between the risk of clinical complications associated with the presence of an antibody in the IgG class (OR 4.15, 95% CI 2.42–7.12, and OR 4.77, 95% CI 2.37–9.61 for aCL and anti-β2GPI, respectively) and in the IgM class (OR 2.2, 95% CI 1.31–3.70, and OR 1.9, 95% CI 1.15–3.14 for aCL and anti-β2GPI, respectively). The postulated inclusion of anti-β2GPI antibody positivity into the previous laboratory criteria changed only slightly the number of patients diagnosed with APS (from 112 to 117). Conclusions: The updated APS classification criteria clearly represent a step forward. However, our results argue against the use of overall positivity for aCL or anti-β2GPI, and favor a clear distinction between the IgG and IgM classes of antiphospholipid ABs. Patients with both LA and anti-β2GPI IgG or LA and aCL IgG positivity may represent the subgroups at the highest risk of thrombotic complications.