Objective: To assess the findings of temporal artery colour duplex sonography (CDS) in GCA characterized by a histological pattern of periadventitial small vessel vasculitis (SVV) and/or vasa vasorum vasculitis (VVV) and compare it with those observed in classic GCA with transmural vasculitis.
Methods: We studied 30 patients with SVV and/or VVV, 63 patients with classic GCA and 67 biopsy-negative patients identified over a 9-year period. CDS of the temporal arteries was performed in all patients by one ultrasonographer. Temporal artery biopsy was used as the reference standard. Sensitivities, specificities and likelihood ratios (LRs) were calculated.
Results: The frequency of the halo sign on CDS was significantly lower in the patients with SVV and/or VVV compared with those with classic GCA (20% vs 82.5%, P = 0.0001). The halo sign had a sensitivity of only 20% (95% CI 8.4, 39.1%) and a specificity of 80.6% (95% CI 68.7, 88.9%) for the diagnosis of SVV and/or VVV. The negative LR was 0.992 (CI 0.824, 1.195), and the positive LR was 1.030 (CI 0.433, 2.451). The halo sign for the diagnosis of biopsy-proven classic GCA had a higher sensitivity of 82.5% (CI 70.5, 90.5%), the same specificity of 80.6% (CI 68.7, 88.9%) and a higher positive LR (4.253; CI 2.577, 7.021).
Conclusion: The halo sign is infrequently found in GCA characterized by a histological pattern of SVV and/or VVV. This limits the sensitivity of CDS in correctly identifying patients with GCA.
Keywords: giant cell arteritis; halo; periadventitial small-vessel vasculitis; transmural vasculitis; ultrasonography.