Utility of biomarkers and temporal artery biopsy length for investigating giant cell arteritis in Western Australia

AIM: To explore demographic characteristics, biopsy length, and blood biomarker performance in an Australian cohort of patients who have undergone temporal artery biopsy (TAB) for giant cell arteritis (GCA). METHODS: We extracted data on biopsies performed for GCA between January 2016 and December 2020 at public hospitals in Perth. Sensitivity, specificity, and area under the curve (AUC) were calculated for blood results. We evaluated the proportion of biopsies with post‐fixation length less than 15 mm and explored several length associations. RESULTS: We retrospectively reviewed biopsies of 360 patients (65.8% female, mean age 72.1 years). Biopsy‐positive patients were older (6.0 years, P < 0.01), and had higher C‐reactive protein (CRP) (44.5 mg/L, P < 0.01), erythrocyte sedimentation rate (ESR) (18.9 mm/h, P < 0.01), and platelets (86.8 × 10(3)/μL, P < 0.01) compared with biopsy‐negative patients. CRP and platelets had the highest AUCs at 0.76 and 0.71, respectively. Sensitivities for CRP and ESR were 96.2% and 91.5%, respectively. Specificities were comparatively low at 41.3% for CRP and 37.4% for ESR. The proportion of biopsies with sub‐optimal length was 55.9% and this varied significantly by site (P < 0.01). Smaller sites performed worse, with a sub‐optimal biopsy rate of 87% amongst the three smallest sites. CONCLUSION: ESR and CRP are helpful preliminary investigations, especially in identifying low‐risk patients, but their specificity is limited. Smaller centers had a higher proportion of biopsies with sub‐optimal length. Considering the importance of biopsy length for TAB diagnostic value, reviewing biopsy data may assist services in developing improvement strategies.