Comment on: Incidence and prevalence of giant cell arteritis in Ontario, Canada: reply

Objective. To estimate trends in the incidence and prevalence of GCA over time in Canada. Methods. We performed a population-based study of Ontario health administrative data using validated case definitions for GCA. Among Ontario residents 50 years of age we estimated the annual incidence and prevalence rates between 2000 and 2018. We performed sensitivity analyses using alternative validated case definitions to provide comparative estimates. Results. Between 2000 and 2018 there was a relatively stable incidence over time with 25 new cases per 100 000 people >50 years of age. Age-standardized incidence rates were significantly higher among females than males [31 cases (95% CI: 29, 34) vs 15 cases (95% CI: 13, 18) per 100 000 in 2000]. Trends in age-standardized incidence rates were stable among females but increased among males over time. Incidence rates were highest among those 70 years of age. Standardized prevalence rates increased from 125 (95% CI 121, 129) to 235 (95% CI 231, 239) cases per 100 000 from 2000 to 2018. The age-standardized rates among males rose from 76 (95% CI 72, 81) cases in 2000 to 156 (95% CI 151, 161) cases per 100 000 population in 2018. Between 2000 and 2018, the age-standardized rates among females similarly increased over time, from 167 (95% CI 161, 173) to 304 (95% CI 297, 310) cases per 100 000 population. Conclusion. The incidence and prevalence of GCA in Ontario is similar to that reported in the USA and northern Europe and considerably higher than that reported for southern Europe and non-European populations. © The Author(s) 2020. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For permissions, please email: journals.permissions@oup.com