Colour-doppler ultrasonography is the first measure to allow objective bedside assessment of Giant Cell Arteritis (GCA). This paper discusses the evidence using the OMERACT filter. Consensus definitions for ultrasonography changes were agreed by Delphi process, with the 'halo' and 'compression' sign being characteristic. The 'halo' is sensitive to change, disappearing within 2-4 weeks of starting glucocorticoids. Ultrasonography has moderate convergent validity with temporal artery biopsy in a pooled analysis of 12 studies including 965 participants (k = 0.44, 95% CI 0.38-0.50). The interobserver and intraobserver reliabilities are good (k = 0.6, k = 0.76-0.78) in live exercises, and excellent when assessing acquired images and videos (k = 0.83-0.87, k = 0.88). Discriminant validity has been tested against stroke and diabetes mellitus (k=-0.16 for diabetes). Machine familiarity and adequate examination time improves feasibility. Ultrasonography in follow-up is not yet adequately defined. Some patients have persistent changes in the larger arteries but these do not necessarily imply treatment failure or predict relapses.
Fiona L Coath, Chetan Mukhtyar