Choroidal thickness as a biomarker of inflammatory activity in patients with polymyalgia rheumatica receiving anti–IL-6 treatment

Objective In corticosteroid-dependent polymyalgia rheumatica (PMR), anti–interleukin-6 (IL-6) therapies are frequently used; however, they may limit the reliability of acute-phase reactants (APRs) as biomarkers of disease activity. Choroidal thickness (CT) may serve as an alternative inflammatory biomarker in these patients. So, the aim of this study is to evaluate changes in CT in patients with PMR initiating anti–IL-6 therapy over 6 months follow-up period, and to assess its correlation and level of agreement with other inflammatory parameters. Methods It is a prospective, observational, longitudinal pilot study. We included 24 patients with PMR who initiated anti–IL-6 therapy. Assessments were performed at baseline (treatment initiation), and at 1 and 6 months. Each visit included a physical examination, musculoskeletal ultrasound of the shoulders and hips, blood tests (including C-reactive protein [CRP]), and CT measurement by optical coherence tomography (OCT). Disease activity was assessed using the PMR Activity Score (PMR-AS) and its imputed version (PMR-ASimp). Results Mean baseline CT was 214 ± 71.13 μm. CT decreased significantly at 1 and 6 months after treatment initiation (208.46 ± 70.03 μm, p < 0.001 and 183.67 ± 70.37 μm, p < 0.001, respectively). A significant correlation was observed between the reduction in CT and the decrease in prednisone dose from 1 to 6 months ( r = 0.417, p = 0.043). No significant correlations were found between CT and the other assessed parameters. Agreement between changes in CT and CRP was 83.3% at 1 month and 79.1% at 6 months. Agreement between changes in CT and PMR indices was 83.3% at both 1 and 6 months. Conclusion In patients with active PMR, CT was increased at baseline and decreased significantly following initiation of anti–IL-6 therapy. Agreement between changes in CT and changes in CRP and PMR indices was high. These findings suggest that CT may be useful as a potential inflammatory biomarker in PMR, although further studies are needed to confirm this hypothesis.