Identification of patients with triple antiphospholipid antibody positivity is platform and method independent.

Abstract

The risk of clinical complications in antiphospholipid syndrome (APS) increases when a patient is positive for all 3 types of antiphospholipid (aPL) antibodies. However, there is a considerable disagreement between various platforms for aCL and anti-β2-glycoprotein I (anti-β2GPI) measurement, which leads to discrepancies between these platforms in assessing aPL antibody positivity. The aim of this retrospective cross-sectional study was to assess whether 2 different platforms, the QUANTA Lite enzyme-linked immunosorbent assay and the QUANTA Flash chemiluminescent immunoassay, identify the same subjects as triple positive in a group of patients with APS and comorbid autoimmune diseases. The study included 220 patients with systemic autoimmune diseases (74 with primary APS; 47 with secondary APS; and 99 with systemic lupus erythematosus without APS). All patients were tested for IgG and IgM aCL and anti-β2GPI antibodies using both platforms. The agreement between the positive results for individual antibodies obtained using both platforms was not full, ranging from 81.8% to 90.9% in a pair-wise comparison. However, the number of patients with triple aPL antibody positivity was similar (80 by QUANTA Lite and 86 by QUANTA Flash); the agreement between the 2 platforms for the identification of patients with triple antibody positivity was 95.5% (Cohen's kappa coefficient = 0.90). This resulted in a similar risk for APS-related clinical complications: an odds ratio of 24.9 for QUANTA Lite and of 24.7 for QUANTA Flash. Our results confirm a strong association between triple aPL antibody positivity and APS and indicate that the identification of patients with triple antibody positivity is platform independent. When aPL antibody profiles are assessed, the agreement between various methods is much higher than that for individual antibodies.