Systemic Lupus Erythematosus (SLE) is associated with an increased cardiovascular disease risk not fully explained by traditional factors. This retrospective study investigated the frequency and clinical relevance of platelet-specific glycoprotein (GP) autoantibodies and antiphospholipid antibodies (aPL) in SLE. Serum from 89 patients with SLE (≥4 ACR 1982 criteria) was analyzed at higher (H) and lower (L) disease activity (median SLEDAI-2K: H = 9.6 and L = 2.1). Platelet GPIIb/IIIa-, GPV- and GPIb/IX-autoantibodies were detected using the indirect Monoclonal Antibody immobilization of Platelet Antigens (MAIPA) assay, while IgM/IgG anti-phospholipid (anti-PL), anti-β2 Glycoprotein 1 (aβ2GP1), anti-cardiolipin (anti-CL), anti-phosphatidylserine/prothrombin complex (anti-PS/PT) and anti-annexin V (anti-AV) antibodies were measured by ELISA. At high activity, 64% (57/89) of patients tested positive for at least one anti-GP antibody, compared to 42% (37/89) with low disease activity. Anti-GPIIb/IIIa prevalence was stable (~30%), whereas anti-GPV and anti-GPIb/IX were more frequent during H (48% 43/89 vs 24% 21/89 and 49% 44/89 vs 27% 24/89, respectively). Anti-GPV levels correlated positively with SLEDAI-2K (r=0.34, p=0.001) and negatively with C3 and C4. Twenty-four patients developed unprovoked thromboembolic events during follow-up. In multivariate analysis, anti-GPV and C3 independently predicted thrombosis (HR 2.17, 95% CI 1.39-3.36, p=0.001 and HR 2.16, 95% CI 1.32-3.54, p=0.002). Platelet counts remained within the normal range irrespective of disease activity, antibody status or thrombotic events. In summary, platelet-specific anti-GP antibodies are prevalent in SLE patients. Anti-GPV, previously not studied in this context and complement C3, independently predicted thrombotic events.
Bengtsson et al. (Thu,) studied this question.