Anti-vimentin/cardiolipin IgA in the antiphospholipid syndrome: a new tool for “seronegative” diagnosis

Antiphospholipid syndrome (APS) is a systemic autoimmune disorder defined by the simultaneous presence of vascular clinical events, pregnancy morbidity and antiphospholipid antibodies (aPL). In clinical practice it is possible to find patients with APS who are persistently negative for the routine aPL tests (“seronegative APS”, SN-APS). Recently, the identification of aPL IgA and/or anti-β2-GPI IgA was shown to represent a further test in SN-APS patients. In this study we analyzed the presence of anti-vimentin/cardiolipin (aVim/CL) IgA in a large cohort of patients with SN-APS, evaluating their possible association with clinical manifestations of the syndrome. This study includes 60 consecutive SN-APS patients, 30 patients with APS and 40 healthy donors. aVim/CL IgA were detected by ELISA. Results show that twelve out of 30 APS patients (40%) and 16/60 SN-APS patients (26.7%) resulted positive for aVim/CL IgA. Interestingly, SN-APS patients tested positive for aVim/CL IgA showed a higher prevalence of arterial thrombosis (p=0.017, likelihood positive ratio of 5.7). This study demonstrates for the first time the presence of anti-Vim/CL IgA in sera of patients with APS. In particular, they revealed a potential usefulness in identification of a significant proportion of SN-APS patients. Moreover, since patients tested positive for aVim/CL IgA reported a high likelihood ratio to have the clinical features of APS, this test may be considered a suitable approach in the clinical evaluation of SN-APS.