In Reply—Giant Cell Arteritis: The Place of 18F-FDG PET/CT and Serum Haptoglobin Level

Abstract

We agree with Dr Yildiz1Yildiz H. Giant cell arteritis: the place of 18F-FDG PET/CT and serum haptoglobin level.Mayo Clin Proc. 2022; 97: 189Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar regarding the ongoing need for identifying readily available, quantifiable blood biomarkers and noninvasive imaging modalities that provide validated assessment strategies to determine disease activity in large-vessel vasculitis, specifically in patients receiving tocilizumab. The findings by Unizony et al2Unizony S. Morris R. Kreuzer J. Haas W. Stone J.H. OP0338 Massspectrometry identifies novel biomarkers in giant cell arteritis, useful in patients on interleukin -6receptor blockade.Ann Rheum Dis. 2020; 79: 207-208Crossref Google Scholar described by Dr Yildiz are noted and provide an area worthy of further investigation and confirmation. We chose to exclude guidance or suggestion of exploratory biomarkers in the recommendations of management because some proposed biomarkers are not commercially available to the practicing clinician. Serum haptoglobin is clinically available but has not yet been validated. Replicability of novel biomarkers across different giant cell arteritis cohorts has been a significant challenge, resulting in several preliminary and promising biomarkers from being used broadly.3Tombetti E. Hysa E. Mason J.C. Cimmino M.A. Camellino D. Blood biomarkers for monitoring and prognosis of large vessel vasculitis.Curr Rheumatol Rep. 2021; 23: 17Crossref PubMed Scopus (9) Google Scholar Thus, the overall utility of serum haptoglobin in the assessment of disease activity in patients with large-vessel vasculitis outside of the GiACTA trial is yet to be known and requires further investigation before routine use can be recommended. The authors agree that 18F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) can provide additional information about the presence of arterial hypermetabolism in the large vessels of patients with giant cell arteritis. The diagnostic accuracy of PET/CT in the diagnosis of large-vessel vasculitis has a pooled sensitivity of 83.3% and specificity of 89.6%4Lee Y.H. Choi S.J. Ji J.D. Song G.G. Diagnostic accuracy of 18F-FDG PET or PET/CT for large vessel vasculitis: a meta-analysis.Z Rheumatol. 2016; 75: 924-931Crossref PubMed Scopus (46) Google Scholar; however, the diagnostic value for monitoring activity while treatment is being received is lower, with a sensitivity of 77% and specificity of 71%.5van der Geest K.S.M. Treglia G. Glaudemans A. et al.Diagnostic values of 18F-FDG-PET/CT for treatment monitoring in large vessel vasculitis: a systematic review and meta-analysis.Eur J Nucl Med Mol Imaging. 2021; 48: 3886-3902Crossref PubMed Scopus (12) Google Scholar Whereas groups have reported that arterial hypermetabolism in some patients portends a higher risk of subsequent aortic complications,6de Boysson H. Liozon E. Lambert M. et al.18F-Fluorodeoxyglucose positron emission tonography and the risk of subsequent aortic complications in giant cell arteritis.Medicine (Baltimore). 2016; 95e3851Crossref Scopus (63) Google Scholar hypermetabolism can also be noted in patients with hypercholesterolemia7Quinn K. Rosenblaum J.S. Rimland C.A. Gribbons K.B. Ahlman M.A. Grayson P.C. Imaging acquisition technique influences interpretation of positron emission tomography vascular activity in large-vessel vasculitis.Semin Arthritis Rheum. 2020; 50: 71-76Crossref PubMed Scopus (17) Google Scholar as well as in vascular remodeling resulting from prior aortic injury8Kim J. Song H.C. Role of PET-CT in the evaluation of aortic disease.Chonnam Med J. 2018; 54: 143-152Crossref PubMed Google Scholar; therefore, interpretation of detectable arterial hypermetabolism in patients without clinical symptoms of disease activity must be done with caution. Large-scale prospective studies using systematically obtained noninvasive imaging are needed to understand the clinical applicability of advanced arterial imaging in the long-term management of patients with large-vessel vasculitis. Until such time, we agree with the current consensus recommendations that arterial imaging (such as PET/CT) is reasonable to use in patients for whom relapse is suspected, if imaging can assist in the confirmation of or exclusion of flare; however, advanced arterial imaging is not routinely recommended for patients in clinical and biochemical remission.9Dejaco C. Ramiro S. Duftner C. et al.EULAR recommendations for the use of imaging in large vessel vasculitis in clinical practice.Ann Rheum Dis. 2018; 77: 636-643Crossref PubMed Scopus (435) Google Scholar Giant Cell Arteritis: The Place of 18F-FDG PET/CT and Serum Haptoglobin LevelMayo Clinic ProceedingsVol. 97Issue 1PreviewI read with great interest the article by Garvey et al.1 They mentioned that treatment with tocilizumab induced a direct inhibition of the acute phase response, and thus C-reactive protein levels are difficult to interpret. This is why identifying active disease or relapse is a challenge in these patients. 18F-Fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) has been proposed as a useful tool to assess response and relapse. However, several studies reported that a complete normalization of PET/CT activity occurred in less than 30% of patients while they are in clinical remission. Full-Text PDF