The Applanation Tonometry in Giant Cell Arteritis (ATOM-GCA) study will answer the following questions:

1. How does PWV, measured by applanation tonometry of temporal arteries, differ between patients with and without a final diagnosis of GCA (based on pre-defined criteria 6 months after inclusion)?

2. What is the diagnostic accuracy and positivity cutoff of the PWV, measured by applanation tonometry, in detecting:

   1. A clinical diagnosis of GCA (based on pre-defined criteria 6 months after inclusion)?
   2. Inflammation of temporal arteries on high-resolution ultrasound?

3. What is the acceptability and adherence of repeat applanation tonometry during the follow-up period in patients with GCA?

ATOM-GCA is a single-center, cross-sectional vanguard study.

Inclusion criteria:

To be included in ATOM-GCA, participants must meet all the following criteria:

1. Age > 50 years.
2. Referral for suspected, new-onset GCA.
3. Ability to understand and willingness to sign an informed consent form.
4. Willingness to comply with study visits and procedures.

Exclusion criteria:

An individual who meets any of these criteria will be excluded from ATOM-GCA:

1. Referral for a suspected GCA relapse.

2. Current use of systemic glucocorticoids, with the following duration at the baseline visit:

   1. ≥ 14 consecutive days of oral glucocorticoids in the previous 30 days, or
   2. ≥ 7 consecutive days of oral glucocorticoids if intravenous glucocorticoids were administered in the previous 30 days.

3. Current use of any conventional or biologic immunosuppressive therapy.

4. Temporal artery biopsy prior to the study visit.

Consecutive patients referred for suspected new-onset GCA