Background/Purpose: At the age of Giant Cell Arteritis (GCA) atherosclerosis is common. The ultrasonographic (US) appearance of athermanous plaque is usually easily differentiated from the hypoechoic halo of GCA. However, the US increase of the intima-media-thickness (IMT) in an atherosclerotic arteries may have a similar appearance as the halo sign (homogenous, hypoechoic wall thickening, well delineated towards the luminal side, visible in longitudinal and transverse planes). The new US high frequencies probes make possible not only to see the halo sign but also measure the increase of the intima-media-thickness (IMT), in this sense the aim of this study was to explore the better cut-off in the IMT of temporal arteries (TA) to minimise the number of false-positive GCA diagnosis caused by atherosclerosis.

Methods: Consecutive non selected patients, ≥50 years-old with high vascular risk according to European Guidelines on cardiovascular disease prevention, and without signs or symptoms of GCA, were included.

Ultrasonography of carotid artery: Carotid US examinations were performed on a Mylab Seven (Esaote Medical Systems, Italy) with a 4–13 MHz linear-array. The system employed dedicated software radiofrequency-tracking technology to obtain IMT (QIMT®).

Ultrasonography of temporal superficial artery: A color Doppler ultrasound (CDU) and grey scale measure of the IMT/halo sign in both TA and its branches was performed by a second experienced sonographer. A Mylab Twice equipment (Esaote, Geneve, Italy) was used, with a 22 MHz frequency for grey scale and a 12.5 MHz for CDU (color gain of 51, PRF of 2 kHz). The sonographer was blind to the clinical and carotid ultrasound IMT data.

Results: Forty patients were studied, 28 men (70%), with a mean age of 70.6 ± 6.9 years. Three patients were active smokers and 27 ex-smokers. Arterial hypertension was present in 39 (97.5%), dyslipidaemia in 34 (85%) and diabetes in 19 (47.5%). The mean erythrocyte sedimentation rate was 13.6 ± 11.0. Eighty carotids were studied, 50 had plaques and 30 did not with a IMT ranged from 0.528 to 1.480 mm. A increase in the carotid IMT is associated with an increase in the IMT of the TA with a weak Spearman correlation (parietal branches 0.282 p = 0.012 and frontal branches 0.228 p = 0.048). The table shows that an IMT > 0.30 mm (halo sign) was seen in at least 1 TA branch of 18 patients (45%) with 33 TA branches affected (20.6%). An IMT cut-off > 0.34 mm, was present in 4 patients (10 %). When at least two affected branches with this measure were required to make the US diagnosis (criteria recommended to improve specificity) only one patient (2.5%) produced a false-positive halo sign.

Conclusion: Carotid atherosclerosis increase the IMT in TA and is a potential cause of false-positive halo sign. We propose a cut-off of AT IMT > 0.34 mm in at least two branches to minimise the number of false positives in GCA diagnosis.