Epidemiology of giant cell arteritis in Waikato, Aotearoa New Zealand

AIM

Giant cell arteritis (GCA) is the most common primary vasculitis in adults over 50 years of age. Our primary objective was to assess the incidence and prevalence of GCA in Waikato in a bid to deepen our understanding of the epidemiology of GCA in Aotearoa New Zealand.

METHODS

From January 2014 to December 2022, cases of GCA were identified prospectively and retrospectively through temporal artery ultrasound request lists and temporal artery biopsy histology reports. Using electronic health records, data were collected retrospectively on patient demographics and clinical features. These were used to calculate the incidence, prevalence and standardised mortality ratio (SMR) of GCA in Waikato.

RESULTS

There were 214 patients diagnosed with GCA over the 9-year period. The majority of patients were European (93.9%, 201/214) with Māori patients being significantly younger than European patients. The mean annual incidence of clinical GCA was 14.7 per 100,000 people over 50 years (95% confidence interval [CI] 12.7-16.6). The SMR was 1.18 (95% CI 0.83-1.52).

CONCLUSION

This is the largest study to date on the epidemiology of GCA in Aotearoa New Zealand. The incidence of GCA is comparable to other studies performed in Aotearoa New Zealand and appears to be stable over time. GCA is uncommon in Māori, Pacific Islander and Asian ethnic groups.

Performance of a fast-track pathway for giant cell arteritis in Waikato, Aotearoa New Zealand

AIMS

Giant cell arteritis (GCA) is the most common primary vasculitis in adults over 50 years of age. To facilitate early diagnosis and reduce harms from corticosteroids and temporal artery biopsies, fast-track pathways have been established. We review the benefits of the fast-track pathway set up in Waikato, Aotearoa New Zealand.

METHODS

Patients were collected prospectively as part of the fast-track pathway from 2014 to 2022. Their records were then reviewed retrospectively to collect data on clinical features, investigations and treatment.

RESULTS

There were 648 individual patients over the study period who had a colour Doppler ultrasound (CDUS) of the temporal arteries. There were 17 true positive CDUS, giving a sensitivity of 10.3% (95% confidence interval [CI] 6.3-15.5%) and specificity of 99.8% (95% CI 99.1-100%). Patients with GCA and a positive scan had significantly fewer steroids than those with GCA and a negative scan (p=0.0037). There were 376 patients discharged after a CDUS who did not have a diagnosis of GCA, resulting in reduced corticosteroid and temporal artery biopsy exposure.

CONCLUSIONS

This is a real-life study that reflects the benefits of fast-track pathways in Aotearoa New Zealand to patients and healthcare systems. It also shows the effect of corticosteroids on positive CDUS, an important consideration when setting up an fast-track pathway.