Background:

Giant cell arteritis (GCA) is a relatively common form of primary systemic vasculitis, which, if left untreated, can lead to permanent sight loss. We compared ultrasound as an alternative diagnostic test with temporal artery biopsy, which may be negative in 9–61% of true cases.

Objective:

To compare the clinical effectiveness and cost-effectiveness of ultrasound with biopsy in diagnosing patients with suspected GCA.

Design:

Prospective multicentre cohort study.

Setting:

Secondary care.

Participants:

A total of 381 patients referred with newly suspected GCA.

Main outcome measures:

Sensitivity, specificity and cost-effectiveness of ultrasound compared with biopsy or ultrasound combined with biopsy for diagnosing GCA and interobserver reliability in interpreting scan or biopsy findings.

Results:

We developed and implemented an ultrasound training programme for diagnosing suspected GCA. We recruited 430 patients with suspected GCA. We analysed 381 patients who underwent both ultrasound and biopsy within 10 days of starting treatment for suspected GCA and who attended a follow-up assessment (median age 71.1 years; 72% female). The sensitivity of biopsy was 39% [95% confidence interval (CI) 33% to 46%], which was significantly lower than previously reported and inferior to ultrasound (54%, 95% CI 48% to 60%); the specificity of biopsy (100%, 95% CI 97% to 100%) was superior to ultrasound (81%, 95% CI 73% to 88%). If we scanned all suspected patients and performed biopsies only on negative cases, sensitivity increased to 65% and specificity was maintained at 81%, reducing the need for biopsies by 43%. Strategies combining clinical judgement (clinician’s assessment at 2 weeks) with the tests showed sensitivity and specificity of 91% and 81%, respectively, for biopsy and 93% and 77%, respectively, for ultrasound; cost-effectiveness (incremental net monetary benefit) was £485 per patient in favour of ultrasound with both cost savings and a small health gain. Inter-rater analysis revealed moderate agreement among sonographers (intraclass correlation coefficient 0.61, 95% CI 0.48 to 0.75), similar to pathologists (0.62, 95% CI 0.49 to 0.76).

Limitations:

There is no independent gold standard diagnosis for GCA. The reference diagnosis used to determine accuracy was based on classification criteria for GCA that include clinical features at presentation and biopsy results.

Conclusion:

We have demonstrated the feasibility of providing training in ultrasound for the diagnosis of GCA. Our results indicate better sensitivity but poorer specificity of ultrasound compared with biopsy and suggest some scope for reducing the role of biopsy. The moderate interobserver agreement for both ultrasound and biopsy indicates scope for improving assessment and reporting of test results and challenges the assumption that a positive biopsy always represents GCA.

Future work:

Further research should address the issue of an independent reference diagnosis, standards for interpreting and reporting test results and the evaluation of ultrasound training, and should also explore the acceptability of these new diagnostic strategies in GCA.

Funding:

The National Institute for Health Research Health Technology Assessment programme.

Article history

The research reported in this issue of the journal was funded by the HTA programme as project number 08/64/01. The contractual start date was in January 2010. The draft report began editorial review in June 2015 and was accepted for publication in July 2016. The authors have been wholly responsible for all data collection, analysis and interpretation, and for writing up their work. The HTA editors and publisher have tried to ensure the accuracy of the authors’ report and would like to thank the reviewers for their constructive comments on the draft document. However, they do not accept liability for damages or losses arising from material published in this report.

Declared competing interests of authors

Raashid Luqmani received honoraria from GlaxoSmithKline (GSK), Nordic and Chemocentryx for training in the use of the Birmingham Vasculitis Activity Score and Vasculitis Damage Index, and personal fees from Roche outside the submitted work. Raashid Luqmani received grants from Fundação para a Ciência e Tecnologia (Portugal), Canadian Institute of Health Research, Arthritis Research UK, Patient Centered Outcomes Research Institute, Oxford University Hospitals NHS Trust Innovation Challenge Competition and Vasculitis UK. Raashid Luqmani has patents pending for a mechanical arm to automate acquisition of ultrasound images and analysis for reviewing ultrasound images. Bhaskar Dasgupta received personal fees from GSK, Servier, Roche, Merck, and Mundipharma and grants from Napp outside the submitted work. Andrew Hutchings was funded by a Medical Research Council special training fellowship in health services research during the development of the study. Jennifer Piper has a patent pending for an ultrasound arm.