Supplement Article |
OP21. ULTRASOUND IN GIANT CELL ARTERITIS
Medical Centre for Rheumatology Berlin-Buch, Berlin, Germany
Background: Several imaging studies have been recently applied in diagnosis of GCA. They display characteristic wall swelling, stenoses, and occlusions of arteries. Since resolution of ultrasound is as high as 0.1 mm, it detects characteristic pathologies not only in axillary and subclavian arteries but also in temporal and other rather small arteries.
Methods: A meta-analysis evaluated 23 studies on temporal artery ultrasound. The author has personally investigated >1000 subjects including >150 patients with active GCA, >25 of whom had large-vessel GCA. Colour Doppler ultrasound evaluates wall swelling. Duplex ultrasound additionally investigates blood flow characteristics for stenoses and occlusions.
Results: The meta-analysis describes a sensitivity of 87% and a specificity of 96% for duplex ultrasound with regard to clinical diagnosis. Sensitivity is similar in our cohort, but specificity is >99%. Results are varying considerably between studies. Sensitivities with regard to histology vary between 40% and 100% for colour Doppler and between 91% and 100% for duplex ultrasound. Specificities vary between 68% and 100% for histology and between 78% and 100% for the clinical diagnosis. According to the meta-analysis a pre-test probability of 10% correlates with post-test probabilities of 71% and 2% for positive and negative ultrasound, respectively. A pre-test probability of 50% correlates with post-test probabilities of 96% and 12%, and a 90% pre-test probability correlates with post-test probabilities of 99% and 55%. Four aspects are essential to receive good results: 1, sonographer experienced in vascular ultrasound who has performed >50 scans of subjects without temporal arteritis to be sure about the appearance of normal temporal arteries; 2, high-end ultrasound equipment with linear probes that cover frequencies of 9–15 MHz; 3, standardised machine adjustments including colour beam steering that make sure that the colour covers exactly the artery lumen; 4, consideration of wall swelling, stenosis, and occlusion for the ultrasound diagnosis. We routinely include ultrasound of the axillary arteries to detect large-vessel GCA. The ultrasound image is identical to that of the temporal arteries. In contrast to the temporal arteries pathologies do not resolve with treatment within two to three weeks but remain for months or years.
Conclusion: Duplex ultrasound of the temporal arteries but also of most of the other arteries is now widely used in diagnosis of GCA. It is a precise imaging study if an experienced sonographer uses good equipment with correct machine adjustments, and considers wall swelling, stenosis, and occlusions.