Audit of temporal artery biopsies for giant cell arteritis performed at the new Royal Adelaide Hospital over a three year period

ABSTRACT

Background: Giant cell arteritis (GCA) is a sight-threatening disease requiring long-term immunosuppression, which carries inherent risk. Temporal artery biopsy (TAB) is the gold-standard investigation to confirm the diagnosis. Guidelines classically recommend a post-fixation sample length of 20 mm to achieve reliable histopathological results, but recent studies suggest sample lengths >6 mm are adequate. Benchmarking/Standard Various papers report a minimum TAB length ranging from >6 mm to >20 mm to avoid false negative histology results. No reports examine the effect of COVID lockdowns on GCA presentations and TABs. Methods: All TABs in South Australia processed by the public state-wide pathology provider from September 2017 until June 2020. Histological diagnosis and sample lengths were extracted from reports. Clinical information and biochemistry for cases at the Royal Adelaide Hospital were derived from medical records. Results: A total of 362 temporal artery biopsies were conducted;156 conducted at Royal Adelaide Hospital, of which 41% were performed by Ophthalmology. Thirty-one percent of Ophthalmology TABs were <10 mm compared to 20% outside Ophthalmology (p = 0.018). TABs performed by Ophthalmology were twice as likely to be positive (34.4% vs 17.2%). Visual symptoms (p = 0.046), older age (p = 0.02), elevated ESR (p = 0.002) and elevated platelets (p = 0.003) were significant predictors of positive histology. Length was not significantly associated with positive histology after adjusting for above factors (p = 0.617). COVID-19 precautions and lockdown in April-May 2020 did not significantly alter the number of TABs. Recommendations: Given that most TABs were performed by Ophthalmology registrars, more direct supervision and techniques such as ultrasound marking may increase sample length. However, TAB lengths <20 mm are acceptable.