Background/Purpose:

Giant cell arteritis (GCA) is a relatively common form of primary systemic vasculitis which if untreated can lead to permanent sight loss. It is a medical emergency, requiring urgent treatment and investigation. We compared the value of ultrasound, as an alternative diagnostic test to temporal artery biopsy, which is typically negative in 10-30% of true cases. Our objective was to compare the effectiveness and cost effectiveness of ultrasound with biopsy in the diagnosis of patients with suspected GCA.

Methods:

We undertook a prospective multicentre cohort study of temporal artery biopsy compared to ultrasound of temporal and axillary arteries for diagnosis of newly suspected GCA. Sonographers received training and examined 10 healthy subjects and 1 patient with active GCA before participating in the study. We recruited patients referred to secondary care with suspected new onset of GCA. The main outcome measures were sensitivity, specificity and cost-effectiveness using a reference diagnosis derived from the final clinical diagnosis, American College of Rheumatology classification criteria for GCA and expert review. Cost-effectiveness analysis compared treatment costs, the impact of steroid toxicity in false-positives and the impact of GCA complications in false-negatives for the two tests and different testing strategies in combination with clinical judgement. 

Results: We recruited 430 patients with suspected GCA from 20 centres between 2010 and 2013. We included 381 patients in the primary analysis (median age 71.1 years; 72% female) and 257 (67%) were given a reference diagnosis of GCA. The sensitivity of biopsy was 39% (95% CI 33-46%), significantly lower than previously published series and inferior to ultrasound (54%, 95% CI 48-60%); the specificity of biopsy was superior to ultrasound (100% vs 81%) compared to the gold standard defined by final diagnosis which included the results of the biopsy. Combining ultrasound with clinical judgement (sensitivity 93%, specificity 77%) was more cost-effective than biopsy with clinical judgement (sensitivity 91%, specificity 81%); incremental net monetary benefit was £493 (€546, US$703) per suspected case. A strategy of ultrasound for all suspected cases followed by biopsy in medium- and high-risk patients with a negative ultrasound was slightly more cost-effective (sensitivity 95%, specificity 77%, incremental net monetary benefit £498 [€552, US$710] per suspected case). 

Conclusion:

We evaluated the role of ultrasound compared to biopsy as diagnostic tests in patients with suspected giant cell arteritis. We demonstrated that as primary investigation of suspected GCA, ultrasound can improve sensitivity but not specificity, when compared to biopsy. A diagnosis of GCA requires clinical assessment, based on the history and examination of the patient; a combined strategy of scanning all patients followed by biopsy of scan negative cases provides an effective and cost effective method to evaluate patients with a medium to high index of suspicion of GCA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-role-of-ultrasound-compared-to-biopsy-of-temporal-arteries-in-the-diagnosis-and-treatment-of-giant-cell-arteritis-a-diagnostic-accuracy-and-cost-effectiveness-study/