Accuracy of Temporal Artery Ultrasound vs Biopsy in the Diagnosis of Giant Cell Arteritis

Giant cell arteritis (GCA) is one of the most concerning conditions encountered by eye care providers because of its potential to be both sight-threatening and life-threatening. Emergent diagnosis and treatment are needed to prevent acute irreversible vision loss and stroke. Although temporal artery biopsy has historically been the gold standard for confirming the diagnosis of GCA, it is invasive with potential complications, not always easily accessible in an emergent time frame, and can have false-negative results owing to skip lesions. In recent years, temporal artery ultrasound has become an emerging diagnostic tool for GCA and has even been regarded by some as the first-line diagnostic procedure in patients with predominantly cranial symptoms of GCA when performed by a skilled sonographer.

In order to test the real-world clinical performance of ultrasound as a first-line diagnostic procedure compared with the current gold standard of clinical diagnosis and biopsy, the authors conducted a cross-sectional study of patients suspected of having GCA over a 10-month period. For all patients, glucocorticoid treatment was initiated, and a diagnostic ultrasound was immediately performed prior to biopsy within 14 days of symptom onset. The diagnostic performance of ultrasound and biopsy in detecting GCA was ultimately compared with the final clinical diagnosis made by experienced physicians at 6-month follow-up.

The study included 78 patients, 35 (45%) of whom were determined to have a clinical diagnosis of GCA at the 6-month follow-up. Of these 35 patients with confirmed GCA, 24 had positive temporal artery biopsy results, with a sensitivity of 0.69. There were no positive biopsy results obtained among those without confirmed GCA, with a specificity of 1.00. Expert sonographers performed the ultrasound procedures, and the diagnostic performance of three separate ultrasonographic features, including compression sign, halo sign, and reduced flow, were compared with that of biopsy. A reduced flow was present in 2 patients in the GCA group and 3 patients in the non-GCA group, with a sensitivity of only 0.06 and a specificity of 0.93. The halo sign, defined as homogenous hyperechoic wall thickening, was positive in 16 patients in the GCA group and 5 patients in the non-GCA group, with a sensitivity of 0.47 and a specificity of 0.77. Positive compression sign, defined as a thickened arterial wall that remains visible upon compression with the ultrasound probe, was positive in 22 patients in the GCA group and 9 patients in the non-GCA group, with a sensitivity of 0.63 and a specificity of 0.79. Thus, the compression sign had the best diagnostic performance among the three ultrasound features and was found to have a sensitivity comparable to that of biopsy for the first-line diagnosis of GCA. This study, therefore, supports recent European League Against Rheumatism recommendations advocating the use of temporal artery ultrasound, when performed by a skilled sonographer, as the first-line imaging examination for diagnosing GCA.

Eye care providers should be aware of the changing guidelines and logistics for GCA diagnosis. Many European hospitals have begun establishing GCA fast-track clinics, which incorporate the use of ultrasound of the temporal artery as a first-line imaging modality for diagnosing GCA; this practice is also starting to gain traction in the United States. In the future, we hope to see more GCA fast-track clinics, with sonographers specifically trained in this area. Eye care providers should investigate whether a GCA fast-track clinic is available through a hospital-based rheumatology department in their geographic region.