Prospective Diagnostic Accuracy of Focused Frontal-Branch Ultrasonography in Giant Cell Arteritis

To evaluate the diagnostic accuracy, reproducibility, and acquisition time of focused bilateral frontal-branch ultrasonography based on intima-media thickness (IMT) in suspected giant cell arteritis (GCA).

In this prospective single-center study, 171 patients underwent color Doppler ultrasonography of the temporal and large arteries and ultrasonography-guided temporal artery biopsy. Bilateral mean frontal-branch IMT was evaluated against the expert diagnosis established at six months. Diagnostic performance was assessed using ROC analysis and multivariable logistic regression. Reproducibility was assessed in 100 randomly selected images.

GCA was diagnosed in 107 patients, including 96 biopsy-positive cases. Mean frontal-branch IMT had the highest observed area under the curve among the temporal artery segments (0.87). At the 0.28-mm cutoff, sensitivity was 71%, specificity 94%, LR+ 11.4, and LR- 0.31. Frontal IMT ≥ 0.28 mm was the strongest independent predictor of GCA (odds ratio 43.0). At a cutoff of ≥3, the exploratory PAMELA (Performance Analysis of a Monosegmental Ultrasonographic Evaluation of the Frontal-Branch of the Superficial Temporal Artery in Giant Cell Arteritis) score had a sensitivity of 74.8% and specificity of 93.7%. Focused bilateral frontal-branch assessment required 1.07 ± 0.24 minutes versus 7.62 ± 1.11 minutes for the complete temporal artery protocol. Intraobserver and interobserver intraclass correlation coefficients were 0.96 and 0.93.

Focused bilateral frontal-branch ultrasonography provides a highly specific, reproducible, and time-efficient initial cranial assessment in suspected GCA. However, the 0.28-mm cutoff and PAMELA score require external validation, and the remaining temporal and large-vessel territories should be examined when frontal findings are negative or equivocal.