Background/Purpose

Ultrasound (US) has not yet superseded temporal artery biopsy as a diagnostic test. This may reflect poor consistency of the scanning technique, due to the lack of a standardised scanning protocol.  We have developed a standardised protocol which was implemented in a prospective study of 857 participants: 439 healthy controls and 418 patients with suspected GCA (Temporal Artery Biopsy versus Ultrasound, TABUL).  We assessed each patient for evidence of typical ultrasound features of GCA: the presence of a halo surrounding the vessel wall, stenosis or occlusion of the vessel.

Methods

A detailed scanning protocol was developed for all cases and controls.  We recorded the presence or absence of ultrasound features of GCA in each segment of each temporal artery (common, parietal, frontal proximal and frontal distal) and both axillary arteries.  Sonographers were asked to acquire video and static images for each patient to ensure accuracy of findings. The sonographer measured and documented: halo diameter (based on a normal range of up to 0.3 mm for the temporal artery and up to 1.0 mm in the axillary artery) and length; pulse Doppler measurements prior to and within a stenosis (confirmed if the highest maximum systolic velocity was over twice the lowest maximum systolic velocity) and arterial occlusion. Each study site sonographer was required to be proficient in the protocol by scanning at least 10 healthy controls, passing an online test showing normal and abnormal scans (pass mark >75%) and scanning a patient with ultrasound evidence of active GCA.

Results

The US scanning protocol was started by 33 sites, with only 22 sites completing the training in 6.7 months [range 0.2 – 16.4 months].  A total of 439 controls were scanned across 31 sites (1 sonographer covered 3 sites).  The online test was passed by 39 sonographers (multiple sonographers at some sites) with an average of 2 attempts [range 1-4]); 22 sonographers successfully scanned an active GCA patient, validated by the expert panel. The longest delay in completing the training was due to difficulty in recruiting a patient with active GCA (hot case), which was necessary for each site prior to it joining the main study. Common issues encountered were a lack of time away from clinical duties and locating a new suspected GCA case for the hot case assessment.

We have created a bank of 857 sets of consistently recorded US images of temporal and axillary arteries from 418 patients with suspected GCA and 439 healthy controls.  Expert review of the first 263 suspected patients has confirmed positive US findings of GCA in 100 patients and no US evidence in 163 cases.

Conclusion

Quality and accuracy are imperative for the clinical use of ultrasound data in the diagnosis of GCA. We have developed an effective training program and scanning protocol which ensures consistency and proficiency. The methodology can be adapted and extended to allow for additional artery assessment, including carotid, vertebral and subclavian arteries, extending the value of a structured approach. We recommend the TABUL study scanning protocol as the standard approach for diagnosis of GCA using ultrasound.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-diagnostic-protocol-for-giant-cell-arteritis-gca-using-ultrasound-assessment/