Anti‐vimentin/cardiolipin IgA in the anti‐phospholipid syndrome: A new tool for ‘seronegative’ diagnosis

Anti‐phospholipid syndrome (APS) is a systemic autoimmune disorder defined by the simultaneous presence of vascular clinical events, pregnancy morbidity and anti‐phospholipid 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 immunoglobulin (Ig)A and/or anti‐β2‐glycoprotein‐I (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 enzyme‐linked immunosorbent assay (ELISA). Results show that 12 of 30 APS patients (40%) and 16 of 60 SN‐APS patients (26.7%) resulted positive for aVim/CL IgA. Interestingly, SN‐APS patients who tested positive for aVim/CL IgA showed a higher prevalence of arterial thrombosis (p = 0.017, likelihood positive ratio = 5.7). This study demonstrates for the first time, to our knowledge, the presence of aVim/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, as 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.