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Vasculitis
Original research
Probability-based algorithm using ultrasound and additional tests for suspected GCA in a fast-track clinic
  1. Alwin Sebastian1,
  2. Alessandro Tomelleri1,2,
  3. Abdul Kayani1,
  4. Diana Prieto-Pena1,3,
  5. Chavini Ranasinghe1 and
  6. Bhaskar Dasgupta1
  1. 1 Rheumatology, Southend University Hospital NHS Foundation Trust, Westcliff-on-Sea, UK
  2. 2 Unit of Immunology, Rheumatology, Allergy and Rare Diseases, San Raffaele Scientific Institute, Milan, Italy
  3. 3 Rheumatology, Marques de Valdecilla University Hospital, Santander, Spain
  1. Correspondence to Bhaskar Dasgupta; bhaskar.dasgupta{at}southend.nhs.uk

Abstract

Objectives Clinical presentations of giant cell arteritis (GCA) are protean, and it is vital to make a secure diagnosis and exclude mimics for urgent referrals with suspected GCA. The main objective was to develop a joined-up, end-to-end, fast-track confirmatory/exclusionary, algorithmic process based on a probability score triage to drive subsequent investigations with ultrasound (US) and any appropriate additional tests as required.

Methods The algorithm was initiated by stratifying patients to low-risk category (LRC), intermediate-risk category (IRC) and high-risk category (HRC). Retrospective data was extracted from case records. The Southend pretest probability score (PTPS) overall showed a median score of 9 and a 75th percentile score of 12. We, therefore, classified LRC as PTPS <9, IRC 9–12 and HRC >12. GCA diagnosis was made by a combination of clinical, US, and laboratory findings. The algorithm was assessed in all referrals seen in 2018–2019 to test the diagnostic performance of US overall and in individual categories.

Results Of 354 referrals, 89 had GCA with cases categorised as LRC (151), IRC (137) and HRC (66). 250 had US, whereas 104 did not (score <7, and/or high probability of alternative diagnoses). In HRC, US showed sensitivity 94%, specificity 85%, accuracy 92% and GCA prevalence 80%. In LRC, US showed sensitivity undefined (0/0), specificity 98%, accuracy 98% and GCA prevalence 0%. In IRC, US showed sensitivity 100%, specificity 97%, accuracy 98% and GCA prevalence 26%. In the total population, US showed sensitivity 97%, specificity 97% and accuracy 97%. Prevalence of GCA overall was 25%.

Conclusions The Southend PTPS successfully stratifies fast-track clinic referrals and excludes mimics. The algorithm interprets US in context, clarifies a diagnostic approach and identifies uncertainty, need for re-evaluation and alternative tests. Test performance of US is significantly enhanced with PTPS.

  • Giant Cell Arteritis
  • Ultrasonography
  • Glucocorticoids
http://creativecommons.org/licenses/by-nc/4.0/

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

https://doi.org/10.1136/rmdopen-2020-001297

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    Footnotes

    • Twitter Bhaskar Dasgupta @profbdasgupta.

    • Acknowledgements All authors would like to thank the Research and Development department at Southend University Hospital.

    • Contributors AS, AT and BD contributed to the conception or design of the work. AT, AK, DP-P, CR and BD contributed to acquisition of data including ultrasound scans which were all done or personally supervised by BD. AS, AT and BD contributed to the analysis or the interpretation of data. All authors were involved in drafting the work or revising it critically for relevant intellectual content. All authors provided final approval of the version published.

    • Funding AS received an international educational (Bresnihan-Molloy) fellowship grant from the Royal College of Physicians of Ireland.

    • Competing interests BD reports grants and personal fees from Roche, personal fees from GSK, BMS, Sanofi and Abbie, outside the submitted work. All other authors have nothing to declare.

    • Patient consent for publication Not required.

    • Ethics approval This is a retrospective study where Research Ethics Committee approval is not required according to the local ethics guidelines.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Data availability statement All data relevant to the study are included in the article or uploaded as supplemental information.

    • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.