Incidence of biopsy-proven giant cell arteritis (GCA) in South Australia 2014-2020

Jem Ninan; Carlee Ruediger; Kathryn A Dyer; Thomas Dodd; Rachel J Black; Suellen Lyne; Ernst M Shanahan; Susanna M Proudman; Susan Lester; Julian McNeil; Catherine L Hill

doi:10.3389/fmed.2023.1173256

Incidence of biopsy-proven giant cell arteritis (GCA) in South Australia 2014-2020

Front Med (Lausanne). 2023 Apr 20:10:1173256. doi: 10.3389/fmed.2023.1173256. eCollection 2023.

Authors

Jem Ninan^{1

2}, Carlee Ruediger^{1

3}, Kathryn A Dyer^{1

3}, Thomas Dodd⁴, Rachel J Black^{1

3

5}, Suellen Lyne^{1

3}, Ernst M Shanahan^{6

7}, Susanna M Proudman^{1

5}, Susan Lester^{1

3}, Julian McNeil^{1

2}, Catherine L Hill^{1

3

5}

Affiliations

¹ Discipline of Medicine, University of Adelaide, Adelaide, SA, Australia.
² Rheumatology Unit, Northern Adelaide Local Health Network, Modbury, SA, Australia.
³ Rheumatology Unit, The Queen Elizabeth Hospital, Woodville, SA, Australia.
⁴ SA Pathology, Adelaide, SA, Australia.
⁵ Rheumatology Unit, Royal Adelaide Hospital, Adelaide, SA, Australia.
⁶ School of Medicine, Flinders University, Bedford Park, SA, Australia.
⁷ Rheumatology Unit, Southern Adelaide Local Health Network, Bedford Park, SA, Australia.

Abstract

Objective: To determine the incidence of biopsy proven giant cell arteritis (GCA) in South Australia.

Methods: Patients with biopsy-proven GCA were identified from pathology reports of temporal artery biopsies at state-based pathology laboratories, from 1 January 2014 to 31 December 2020. Incidence rates for biopsy-proven GCA were calculated using Australian Bureau of Statistics data for South Australian population sizes by age, sex, and calendar year. Seasonality was analyzed by cosinor analysis.

Results: There were 181 cases of biopsy-proven GCA. The median age at diagnosis of GCA was 76 years (IQR 70, 81), 64% were female. The estimated population incidence for people over 50 was 5.4 (95% CI 4.7, 6.1) per 100,000-person years. The female: male incidence ratio was 1.6 (95% CI 1.2, 2.2). There was no ordinal trend in GCA incidence rates by calendar year (p = 0.29). The incidence was, on average, highest in winter, but not significantly (p = 0.35). A cosinor analysis indicated no seasonal effect (p = 0.52).

Conclusion: The incidence of biopsy-proven GCA remains low in Australia. A higher incidence was noted compared to an earlier study. However, differences in ascertainment and methods of GCA diagnosis may have accounted for the change.

Keywords: South Australia; biopsy; giant cell arteritis (GCA); incidence; positive.