Background The diagnosis of giant cell arteritis (GCA) remains a clinical one. Temporal artery (TA) ultrasound (US) has been proposed as a new diagnostic tool in GCA.
Objectives To assess the performance characteristics of TA US and biopsy in routine clinical practice.
Methods All patients presenting with suspected GCA to our institutions are recruited to a prospective registry. Patients who had both a TA US and biopsy performed at the time of presentation were included in the current study. US was performed by 2 radiologists. The performance characteristics of both tests were compared to physician diagnosis at six months following presentation. Predictive factors for positive US and biopsy were explored in univariate and multivariable logistic regression analyses.
Results 162 patients were included, 123 (76%) with GCA. Mean (SD) duration of glucocorticoids was 6.6 days (19.4) at the time of TA US and 6.2 days (8.4) at the time of TA biopsy. US had a sensitivity of 52.8% (95% CI 43.7, 61.9) and specificity of 71.8% (95% CI 54.9, 84.5). There were 11 false positive US results; 5 with migraine, 2 other vasculitides, 2 local infections, 2 malignancies. Biopsy had a sensitivity of 48.8% (95% CI 39.7, 57.9) and specificity of 97.4% (95% CI 84.9, 99.9). A hypothetical sequential strategy of US followed by biopsy in the case of negative US had a sensitivity of 78.9% (95% CI 70.1, 85.5) and specificity of 71.8% (95% CI 54.9, 84.5), equivalent to a simultaneous testing strategy. Time on glucocorticoids did not significantly impact the results of US or biopsy. The only factor independently predictive of a positive US was male sex (OR 5.53, 95% CI 2.72 to 11.22, p<0.001). The only factor independently predictive of a positive biopsy was jaw claudication (OR 2.40, 95% CI 1.11, 5.21, p=0.027).
Conclusions TA US is a useful tool in the diagnosis of GCA; however false positive tests occur in 7% and thorough clinical assessment remains crucial. Prior glucocorticoid treatment has no clear impact on results.
Disclosure of Interest None declared