Diagnostic use of ultrasound in giant cell arteritis in Counties Manukau District Health Board, New Zealand

Abstract

Objectives A retrospective observational study was undertaken to assess the diagnostic performance (sensitivity and specificity) of colour duplex ultrasound (CDUS) compared with temporal artery biopsy (TAB) for the diagnosis of GCA in Counties Manukau District Health Board (CMDHB), New Zealand using clinical diagnosis as the reference standard. Methods The study population included patients with clinically suspected GCA who were referred to Middlemore hospital and underwent either CDUS or TAB, or both, between January 2019 and December 2020. Results Sixty-nine patients were included in the study. Sixty-one percent were over the age of 75, with no cases below 50 years and a female predominance of 71%. The sensitivity of CDUS was 26% [95% confidence interval (CI) 10% to 48%] and specificity 97% (95% CI 84% to 100%). The sensitivity of TAB was 57% (95% CI 34% to 77%) and specificity 100%. CDUS had a positive predictive value of 86% (95% CI 42% to 99%) and a negative predictive value of 65% (95% CI 49% to 78%). Conclusion Positive CDUS in patients with high risk for GCA may preclude the need for TAB due to the high specificity of CDUS in GCA. In contrast, patients with high risk for GCA with negative CDUS may still need TAB to confirm or exclude GCA. The duration from commencement of steroids to the time of CDUS is crucial in confirming GCA and for this, shortening waiting time in CMDHB would be necessary to ensure adequate test performance in practice.

Giant cell arteritis: A population-based retrospective cohort study exploring incidence and clinical presentation in Canterbury, Aotearoa New Zealand

“…Numerous methods for case ascertainment were applied to capture such patients; however, it is not possible to quantify how many may have been missed across various sectors. While this number is expected to be small, it may explain why the incidence seen in our cohort is slightly lower than that reported by Abdul-Rahman and Nagarajah ( 3 , 4 ). Finally, the cases of LV-GCA may suffer from selection bias, as imaging was performed at the discretion of the treating clinician, and therefore only those with symptoms of LV extra-cranial involvement underwent LV imaging.…”

“…Demographics are similar to those previously reported in NZ, with a mean age of 74.2 years, female predominance (incidence ratio 1.59), and primarily affecting those of European descent (93%). The mean annual incidence for biopsy-proven GCA was marginally lower than that reported elsewhere in NZ (3,4), at 10.5 per 100,000 over the age of 50, but correlates with a large population study from the UK (18), where many NZ Europeans in Canterbury are descendant. There were no differences in demographics between the LV-and C-GCA cohorts, which contrasts existing literature suggesting LV-GCA patients have a younger age at diagnosis (11,19,20), and may be a consequence of our small case numbers.…”

“…Little work has been published on the epidemiology of GCA in Aotearoa New Zealand (NZ). One retrospective cohort study reported a mean annual incidence of 12.7 per 100,000 over the age of 50 for biopsy-proven GCA ( 3 ) and a recent study assessing diagnostic performance of color duplex ultrasound reported an incidence in NZ Europeans and Māori of 13.2 and 12.2, respectively ( 4 ). Additional work has been conducted exploring seasonal influence on rates of GCA in NZ, with no meaningful trends identified ( 5 ).…”

Epidemiology of systemic vasculitis

“…In the second study from Counties Manukau District Health Board, New Zealand, it was 11.4 (95% CI 7.8–16.7) per 100 000 when all biopsy-proven and biopsy-negative cases were included. This study also demonstrated that GCA can manifest in different ethnicities, including the Maori population and Pacific Islanders [7].…”

Te hauora karu o te iwi Māori: A comprehensive review of Māori eye health in Aotearoa/New Zealand

“…There is limited published data on the epidemiology of giant cell arteritis (GCA) in Māori. One observational study of 69 patients in the Counties Manukau district found 9.7% of positive GCA cases were Māori 92 . Another study conducted in the Otago region of the South Island examined 363 consecutive patients with biopsy‐proven GCA of which 7.1% were of Māori descent 93…”