Diagnostic performance and utility of very high-resolution ultrasonography in diagnosing giant cell arteritis of the temporal artery

Objective: Very-high resolution US (VHRU; 55 MHz) provides improved resolution and could provide non-invasive diagnostic information in GCA of the temporal artery. The objective of this study was to assess the diagnostic utility of VHRU-derived intima thickness (VHRU-IT) in comparison to high-resolution US halo-to-Doppler ratio (HRU-HDR) in patients referred for temporal artery biopsy. Methods: VHRU and HRU of the temporal artery were performed before a biopsy procedure in 78 prospectively recruited consecutive patients who had received glucocorticoid treatment for a median of 8 days (interquartile range 0-13 days) before imaging. Based on the final diagnosis and biopsy findings, the study population was divided into the following four groups: non GCA (n = 40); clinical GCA with no inflammation on biopsy (n = 15); clinical GCA with inflammation limited to adventitia (n = 9); and clinical GCA with transmural inflammation (TMI; n = 11). Results: Both VHRU and HRU were useful for identifying subjects with TMI, with VHRU outperforming HRU (area under curve: VHRU-IT 0.99, 95% CI 0.97, 1.00; HRU-HDR 0.74, 95% CI 0.52, 0.96; P=0.026). The diagnostic utility for diagnosing clinical GCA (negative biopsy) or inflammation limited to the adventitia was poor for both VHRU and HRU-HDR. From 5 days after initiation of glucocorticoid treatment, VHRU-IT was increased in eight of nine patients, whereas HRU-HDR was positive in three of seven patients. Both methods showed excellent inter-observer agreement (Cohen's κ: VHRU-IT 0.873; HRU-HDR 0.811). Conclusion: In suspected GCA, VHRU allows non-invasive real-time imaging of TMI manifestations of the temporal artery wall. VHRU-derived intimal thickness measurement seems to be more sensitive than the halo sign and HRU-HDR in detecting TMI in patients with prolonged glucocorticoid treatment.