ORIGINAL ARTICLE Abnormalities at three musculoskeletal sites on whole-body positron emission tomography/computed tomography can diagnose polymyalgia rheumatica with high sensitivity and specificity Claire E. Owen 1,2 & Aurora M. T. Poon 2,3 & Victor Yang 1 & Christopher McMaster 1 & Sze Ting Lee 2,3,4 & David F. L. Liew 1,2 & Jessica L. Leung 1,2 & Andrew M. Scott 2,3,4 & Russell R. C. Buchanan 1,2 Received: 7 October 2019 /Accepted: 17 February 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract Purpose To evaluate the sensitivity and specificity of PET/CT findings in PMR and generate a diagnostic algorithm utilizing a minimum number of musculoskeletal sites. Methods Steroid-naïve patients with newly diagnosed PMR (2012 EULAR/ACR classification criteria) were prospec- tively recruited to undergo whole-body 18 F − FDG PET/CT. Each PMR case was age- and sex-matched to four PET/ CT controls. Control scan indication, diagnosis and medical history were extracted from the clinical record. Qualitative and semi-quantitative scoring (maximum standardized uptake value [SUV max ]) of abnormal 18 F-FDG uptake at 21 musculoskeletal sites was undertaken for cases and controls. Results informed the development of a novel PET/CT diagnostic algorithm using a classification and regression trees (CART) method. Results Thirty-three cases met the inclusion criteria and were matched to 132 controls. Mean age was 68.6 ± 7.4 years for cases compared with 68.2 ± 7.3 for controls, and 54.5% were male. Median CRP was 49 mg/L (32–65) and ESR 41.5 mm/h (24.6–64.4) in the PMR group. The predominant control indication for PET/CT was malignancy (63.6%). Individual musculoskeletal sites proved insufficient for diagnostic purposes. A novel algorithm comprising 18 F-FDG uptake ≥ 2 adjacent to the ischial tuberosities in combination with either abnormalities at the peri-articular shoulder or interspinous bursa achieved a sensitivity of 90.9% and specificity of 92.4% for diagnosing PMR. Conclusions The presence of abnormal 18 F-FDG uptake adjacent to the ischial tuberosities together with findings at the peri- articular shoulder or interspinous bursa on whole-body PET/CT is highly sensitive and specific for a diagnosis of PMR. Trial registration Clinical Trial Registration: Australian New Zealand Clinical Trials Registry, http://www.anzctr.org.au, ACTRN1261400696695 Keywords Polymyalgia rheumatica . Whole-body positron emission tomography/computed tomography . Diagnosis . Sensitivity . Specificity This article is part of the Topical Collection on Infection and inflammation Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00259-020-04731-z) contains supplementary material, which is available to authorized users. * Claire E. Owen claire.owen@austin.org.au 1 Department of Rheumatology, Austin Health – Repatriation Campus, Level 1, North Wing, 300 Waterdale Road, Heidelberg West, VIC 3081, Australia 2 Department of Medicine, University of Melbourne, Parkville, VIC, Australia 3 Department of Molecular Imaging and Therapy, Austin Health, Heidelberg, VIC, Australia 4 Olivia Newton-John Cancer Research Institute, and School of Cancer Medicine, La Trobe University, Heidelberg, VIC, Australia European Journal of Nuclear Medicine and Molecular Imaging https://doi.org/10.1007/s00259-020-04731-z