Diagnostic yield of axillary artery ultrasound in addition to temporal artery ultrasound for the diagnosis of giant cell arteritis.

OBJECTIVES

There are limited data on the additional diagnostic yield of axillary artery ultrasound (axUS) in addition to temporal artery ultrasound (tempUS) for the diagnosis of giant cell arteritis (GCA).

METHODS

Retrospective study of consecutive patients with suspected GCA who underwent a standardized axUS and tempUS between 01/2015 and 03/2017. The diagnostic yield of axUS in addition to ultrasound of the temporal arteries with respect to the final clinical diagnosis was assessed, with a positive axUS defined as circumferential, hypoechogenic thickening of the far wall axillary artery intima media thickness (axIMT) ≥1.3 mm. A subgroup of patients underwent PET-CT within one week before or after the sonographic study. Separate analyses were performed regarding certain subgroups according to clinical presentation and to clinical pre-test probability for cranial GCA.

RESULTS

Out of 228 patients, 92 received a final diagnosis of GCA. From the 92 patients with a final diagnosis of GCA, 50 (54.3%), 13 (14.1%) and 15 (16.3%) had a positive tempUS, positive axUS, and combined positive tempUS and axUS, respectively. The sensitivity of sonographic imaging for the final diagnosis of GCA increased from 69.6% to 84.8%, when axUS results were considered in addition to tempUS, while the specificity remained high (no false positive axUS). The diagnostic yield of axUS was highest in patients with a low clinical probability of cranial GCA and lowest in patients with symptoms of ocular ischemia. We observed a substantial rate (42.1%) of discordant results between axUS and PET-CT in a subgroup of 38 patients.

CONCLUSIONS

In conclusion, axUS offers a substantial diagnostic yield in addition to tempUS in subjects with suspected GCA, mainly in those subjects with low clinical probability for cranial GCA.