AB0672 18f-fdg whole body pet/ct as a diagnostic test for polymyalgia rheumatica in patients with normal inflammatory markers

Background Despite abnormal C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) being required in the 2012 EULAR/ACR classification criteria, 7%–20% of polymyalgia rheumatica (PMR) patients possess normal inflammatory markers at diagnosis. 1 A characteristic pattern of 18 F-fluorodeoxyglucose ( 18 F-FDG) uptake is seen on whole body positron emission tomography/computed tomography (PET/CT) in PMR, hence this imaging modality may be a useful diagnostic test in this clinical scenario. Objectives To report the utility of whole body PET/CT for diagnosing PMR in patients with normal inflammatory markers and compare the clinical and radiologic characteristics of this subgroup with patients from the Melbourne Predictors of Relapse in PMR (MPR-PMR) study. Methods Patients presenting with clinical features of PMR according to the 2012 EULAR/ACR classification criteria but normal CRP and ESR underwent 18 F-FDG PET/CT as part of their diagnostic work-up. A whole body scan from skull vertex to feet (including dedicated hand views) was performed using the Phillips T/F machine prior to prednisolone commencement. Qualitative and semi-quantitative (standardised uptake value maximum [SUV max ]) scoring of abnormal 18 F-FDG uptake was undertaken. Newly diagnosed and untreated PMR patients who underwent the same 18 F-FDG PET/CT protocol as part of the MPR-PMR study were used as the comparator group. Statistical analysis was conducted using Stata 13.1 (StataCorp, College Station, TX, USA). Results Three patients with normal inflammatory markers (Median CRP 1 [0.9–2], median ESR 6 1 – 7 ) underwent 18 F-FDG PET/CT. Mean age was 60.15±7.55 years, two patients (66.67%) were male and all were Caucasian. Shoulder and hip pain was present in all cases, but only one patient reported peripheral joint involvement. Median early morning stiffness (EMS) was 30 min. 15 – 60 On whole body PET/CT, characteristic 18 F-FDG uptake was visualised in each patient at the shoulder capsule, trochanteric bursae and adjacent to the ischial tuberosities, with hip capsule involvement similarly present in 2/3. When compared with 35 patients from the MPR-PMR study, there were no statistically significant differences in the clinical characteristics nor the distribution or intensity of abnormal 18 F-FDG uptake between the two populations. Conclusions In patients with suggestive clinical features but normal inflammatory markers, whole body PET/CT may be utilised to confirm a diagnosis of PMR. Reference [1] Cantini F, Salvarani C, Olivieri I, et al. Erythrocyte sedimentation rate and C-reactive protein in the evaluation of disease activity and severity in polymyalgia rheumatica: a prospective follow-up study. Seminars in Arthritis u0026 Rheumatism. 2000;30(1):17–24. Disclosure of Interest None declared