Giant cell arteritis: A nationwide, population-based cohort study on incidence, diagnostic imaging, and glucocorticoid treatment.

Aim: The study investigated the development over time of the incidence, diagnostic imaging, and treatment of giant cell arteritis (GCA).

Method: This nationwide, population-based cohort study was conducted in Denmark using medical and administrative registries. Incident GCA cases from 1996-2018 were defined as patients aged ≥50 years registered with a first-time GCA diagnosis and ≥3 prescriptions for glucocorticoids (GCs) within 6 months after diagnosis. We determined incidence rates of GCA, the proportion of patients still receiving GCs >2 years after diagnosis, the proportion of patients receiving temporal artery biopsies (TAB) and diagnostic imaging including ultrasound, positron emission tomography, magnetic resonance, and/or computed tomography angiography at the time of diagnosis.

Results: We identified 9908 incident GCA cases. The incidence rates of GCA remained stable at 19-25 per 100,000 people aged >50 years from 1996-2018. The proportion of GCA patients receiving a TAB remained constant until 2016, after which it promptly declined from 70-80% to 29-39%. In contrast, the proportion of patients receiving diagnostic imaging increased from 2% to 66% from 2000-2018. The proportion of GCA patients remaining in GC treatment has steadily decreased from 1996-2016, but remains high at 64%, 40%, and 34% after 2, 5, and 10 years following the diagnosis, respectively. The cumulative GC dose has remained relatively stable.

Conclusion: Incidence rates of GCA have remained stable since 1996 despite increasing use of diagnostic imaging. There is a clear discrepancy between current international GCA treatment guidelines and the clinical practice up to 2018.