Currently submitted to: JMIR Research Protocols
Date Submitted: Jun 11, 2026
Open Peer Review Period: Jun 11, 2026 - Aug 6, 2026
(currently open for review)
Warning: This is an author submission that is not peer-reviewed or edited. Preprints - unless they show as "accepted" - should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.
Temporal artery applanation tonometry in giant cell arteritis (ATOM-GCA Pilot): Protocol for a single-center prospective pilot study
ABSTRACT
Background:
Giant cell arteritis (GCA) is the most common systemic vasculitis affecting adults over 50 years of age. Early diagnosis remains challenging because currently available diagnostic tools have important limitations. Applanation tonometry is a non-invasive vascular assessment technique that measures pulse wave velocity (PWV), a marker of arterial stiffness. Inflammation of the temporal arteries in GCA may alter arterial mechanical properties and could be detected through changes in PWV.
Objective:
The Applanation Tonometry in Giant Cell Arteritis (ATOM-GCA) pilot study aims to evaluate differences in temporal artery PWV between patients with and without GCA and to assess the feasibility, reliability, and acceptability of temporal artery applanation tonometry in patients undergoing investigation for suspected GCA.
Methods:
ATOM-GCA is a prospective, single-center pilot study conducted within the Canadian Vasculitis Research Network. Consecutive adults undergoing evaluation for a new episode of suspected GCA will undergo applanation tonometry of four temporal artery segments performed by two independent operators. Standard diagnostic assessments, including clinical evaluation, laboratory testing, and temporal artery ultrasound, will be performed by separate investigators blinded to tonometry findings. A centralized adjudication committee, blinded to tonometry results, will assign the final diagnosis of GCA after 6 months of follow-up. The primary outcome is the adjusted difference in temporal artery PWV between patients with and without GCA, modeled using predefined covariates to account for potential confounding factors. Secondary outcomes include recruitment feasibility, operational feasibility, intra- and inter-rater reliability, patient acceptability, and adherence to repeat tonometry assessments. Exploratory analyses will evaluate longitudinal changes in PWV during remission and relapse. A sample size of 146 participants will provide 90% power to detect a clinically meaningful between-group difference of 1 m/s in PWV.
Results:
The study has received ethics approval from the CIUSSS du Nord-de-l’Île-de-Montréal Research Ethics Committee. Participant recruitment started in 2025 and continue over approximately 24 months. Data collection and follow-up are anticipated to be completed by the end of 2027, with primary analyses and dissemination of results planned thereafter.
Conclusions:
The ATOM-GCA pilot study will provide the first prospective evaluation of temporal artery applanation tonometry as a diagnostic tool in GCA. If successful, this technology could offer non-invasive, and widely accessible method to support the diagnosis and monitoring of GCA and inform the design of future multicenter validation studies. Clinical Trial: ClinicalTrials.gov identifier: NCT05703763
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