ANTICARDIOLIPIN ANTIBODIES AND ACTIVITY OF GIANT CELL ARTERITIS

Background: Anticardiolipin antibodies (aCL) can be detected in newly diagnosed GCA as reactive antibodies to endothelial lesions. Their prognostic role, as a marker of disease activity, has not been extensively studied in GCA. Objectives: Our aim was to determine whether aCL IgG might represent laboratory marker of active GCA. Methods: We included patients with new clinical diagnosis of GCA supported by histology or imaging between September 2011 and July 2019, who completed at least a 48-week follow-up at our secondary/tertiary rheumatology center. Follow up visits with predetermined clinical and laboratory tests, including aCL IgG, were performed 12, 24, 48, and 96 weeks after diagnosis. GCA relapse was defined as worsening or new disease activity after initial remission. Other reasons for the disease-related symptoms, elevated inflammatory markers (C reactive protein or erythrocyte sedimentation rate) had to be excluded. aCL IgG were determined in the patients’ sera samples at baseline and at follow up visits, using an in-house solid phase enzyme-linked immunosorbent assay . A value above the 99 percentile of the healthy control population was taken as significant. Results: During the observation period we identified 288 newly diagnosed GCA patients. Two hundred and twelve GCA patients (66.5% females, median (IQR) age 73.9 (67.0–78.7) years) fulfilled the study inclusion criterion, among them 145 patients completed the 96-week follow up visit. At baseline, 129/212 (60.8%) GCA patients had positive aCL IgG. During in total 781 follow up visits, we recorded 77 (9.9%) episodes of active/relapsing GCA (clinical, laboratory or combined in 4 (5.2%), 48 (62.3%), 25 (32.5%) episodes, respectively). aCL IgG were present at 155/781 (19.8%) measurements (at 24/77 episodes of relapsing/active and 131/573 episodes of quiescent GCA). The correlation between active/relapsing GCA and aCL IgG positivity was only weekly positive (r coefficient=0.094; p= 0.015). Conclusion: The role of aCL IgG as a biomarker for GCA activity seems to be rather limited. REFERENCES: [1]Božič B, et al. Int Arch Allerg Immunol. 1997; 112:19-26. doi.org/ 10.1159/000237426 Disclosure of Interests: None declared Citation: Ann Rheum Dis, volume 80, supplement 1, year 2021, page 1201Session: Vasculitis – large vessel vasculitis (Publication Only)