Sir, We read with interest the recent article by Monti et al.  describing the experience of Nutfield Orthopaedic Centre’s Rheumatology Department in utilizing colour duplex sonography (CDS) of the superficial temporal (STA) and axillary arteries to assist in diagnosing GCA and monitoring disease flares. This publication follows on from the recent Temporal Artery Biopsy vs ULtrasound in Diagnosis of GCA (TABUL) study , which also assessed the diagnostic role of CDS in a large number of suspected GCA patients. We commend the authors for adding to the body of knowledge in this area and do feel there is an important role for duplex US in the assessment of patients with GCA. We do, however, have a number of reservations regarding the reported specificity of 100% in patients scanned within 7 days and the implicit suggestion that temporal artery biopsy (TAB) may not be required in this group. Indeed, this appears to be the current practice of the authors. Our concerns relate to study methodology, prior US literature describing variable diagnostic accuracy in suspected GCA patients, placing the same prognostic weight on a positive CDS as a TAB and our own experience assessing patients with GCA and atherosclerosis in our dedicated vascular US laboratory. The reference standard in this study was the clinical diagnosis made by the treating rheumatologist who was aware of the US results. Unblinding of the CDS findings undermines the independence of the reference standard from the index test (CDS) and raises concerns about the robustness of the reported diagnostic accuracy . Importantly, the perfect specificity of 100% of a halo on CDS for GCA reported for patients scanned within 7 days compares with a much lower specificity of 81% in the TABUL study where clinicians were blinded at the 2 week clinical review . Given this diagnostic uncertainty, we would also caution against disregarding the value of a TAB in patients with a positive CDS. While the authors describe studies reporting false-negative TAB results in up to 60% of GCA cases, literature in this area is fraught with many poor-quality studies and varying gold standards. One important large study that established the prognostic importance of TAB described a false-negative TAB rate of just 9%. This was in a cohort where biopsy-negative patients were followed for extended periods without long-term corticosteroid treatment . In Monti et al.’s cohort , nine patients with a positive CDS underwent TAB. Of these, only four (44%) had a positive TAB. This is in keeping with another recent paper published in this journal  where only 13/23 (57%) patients with a halo on CDS had corresponding transmural inflammation on US-guided biopsy. Clearly a halo on CDS does not equate with a positive TAB and thus clinicians must be mindful of not attributing the prognostic implications of a positive TAB to patients with a halo on CDS. Our final comment regarding this study relates to our own dedicated vascular US laboratory experience. As a centre that scans patients for primary vascular diseases, we have found that patients with traditional or novel cardiovascular risk factors with atherosclerosis of the carotid arteries may exhibit increased intima-media thicknesses of the axillary artery in the absence of vasculitis. Indeed, it is not uncommon for these patients to have an axillary intima-media thickness of >1 mm. Furthermore, our centre is reluctant to report vasculitis of the STA in the absence of clearly hypoechoic artery walls with a thickness ⩾0.6 mm. We believe that the minimum wall thickness cut-offs quoted by Monti et al.  for axillary arteries of 0.9 mm and STA of 0.4 mm may be normal for some patients with atherosclerotic disease. Further study is clearly needed to better define the confounding effects of atherosclerosis on axillary and STA wall thickness . In summary, we applaud Monti et al.  for their report of temporal and axillary artery US findings in their GCA cohort. However, we caution clinicians against inferring from this study that a positive CDS has a specificity of 100% for GCA and that a halo on CDS has the same prognostic implications as a positive TAB. Funding: No specific funding was received from any bodies in the public, commercial or not-for-profit sectors to carry out the work described in this article. Disclosure statement: The authors have declared no conflicts of interest. References 1 Monti S , Floris A , Ponte CB et al. The proposed role of ultrasound in the management of giant cell arteritis in routine clinical practice . Rheumatology 2018 ; 57 : 112 – 19 . Google Scholar CrossRef Search ADS PubMed 2 Luqmani R , Lee E , Singh S et al. The role of ultrasound compared to biopsy of temporal arteries in the diagnosis and treatment of giant cell arteritis (TABUL): a diagnostic accuracy and cost-effectiveness study . Health Technol Assess 2016 ; 20 : 1 – 270 . Google Scholar CrossRef Search ADS PubMed 3 Whiting PF , Rutjes AW , Westwood ME et al. QUADAS-2: a revised tool for the quality assessment of diagnostic accuracy studies . Ann Intern Med 2011 ; 155 : 529 – 36 . Google Scholar CrossRef Search ADS PubMed 4 Hall S , Persellin S , Lie JT et al. The therapeutic impact of temporal artery biopsy . Lancet 1983 ; 2 : 1217 – 20 . Google Scholar CrossRef Search ADS PubMed 5 Germano G , Muratore F , Cimino L et al. Is colour duplex sonography-guided temporal artery biopsy useful in the diagnosis of giant cell arteritis? A randomized study . Rheumatology 2015 ; 54 : 400 – 4 . Google Scholar CrossRef Search ADS PubMed 6 De Miguel E , Beltran LM , Monjo I , Deodati F , Schmidt WA , García-Puig J. Ultrasound cut-off in giant cell arteritis: a solution to arteriosclerosis pitfall in the halo sign [abstract] . Arthritis Rheumatol 2017 ; 69(Suppl 10) :abstract 261. © The Author(s) 2018. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: email@example.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)
Rheumatology – Oxford University Press
Published: Mar 2, 2018
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