PET/CT as a Diagnostic Test for Polymyalgia Rheumatica

Patients with suspected polymyalgia rheumatica (PMR) will be recruited and given information (in paper or electronic format) outlining the research project’s purpose, and participant involvement will be provided to eligible patients by a study investigator. All participants will be eligible for the associated sub-study “Predicting Autoimmunity” as they have an autoimmune rheumatic disease, with participation involving the additional collection of one heparin-containing, one EDTA-containing and one serum gel tube of blood at baseline and the 6-month follow-up visit. No additional time is required to complete this sub-study, as the biomarkers collected will be simply added to the existing biobank. Following enrolment, a baseline study visit (face-to-face) will be scheduled in the Rheumatology Department at Heidelberg Repatriation Hospital. Morning visits will be arranged (when PMR symptoms are typically at their worst). The estimated duration is 1 hour. The following clinical data will be collected: 1) Demographic: date of birth, sex and race. 2) History: disease onset, distribution of joint involvement (marked on a patient mannequin), severity of pain (Numeric Rating Scale [NRS]), severity (NRS) and duration of early morning stiffness (mins), and presence of constitutional symptoms (loss of weight [kg], fever and fatigue). 3) Examination: vital signs, body mass index, peripheral joint swelling/joint line tenderness and shoulder range of movement (elevation of upper limb score and goniometer degree). 4) Patient-reported outcomes: Visual Analogue Scale (VAS), Health Assessment Questionnaire-Disability Index (HAQ-DI), 36-item Short Form Survey (SF-36) and Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F). In order to generate a PMR-Activity Score (PMR-AS), the study investigator will also complete a Physician Global Score (PGS). Baseline investigations will comprise: 1) Laboratory: FBE, UEC, LFTs, CRP, ESR, rheumatoid factor, ACPA, ANA, ANCA, CK, TSH, Vitamin D, HbA1C and “Predicting Autoimmunity” samples for novel biomarker testing if opted in; 2) Radiology: x-ray of hands (to assess for erosive change), performed in the Radiology Department at Heidelberg Repatriation Hospital. 3) Whole body PET/CT: within 7 days of enrolment, performed in the Centre for Molecular Imaging and Therapy at the Austin Hospital using the Phillips PET/CT camera. This visit will take approximately 2 hours. Qualitative evaluation of 18F-FDG uptake at those musculoskeletal sites included in the Heidelberg algorithm and concise Leuven/Groningen score (the “simplified” methods for diagnosing PMR) will be undertaken by two experienced Nuclear Medicine Physicians, both of whom will not be privy to additional clinical information and will not require any further training given their experience with these methods. The Heidelberg algorithm utilises pre-specified qualitative scoring of abnormal 18F-FDG uptake at just three musculoskeletal sites – adjacent to the ischial tuberosities, in combination with either the peri-articular shoulder or interspinous bursa (Owen et al. Abnormalities at three musculoskeletal sites on whole-body positron emission tomography/computed tomography can diagnose polymyalgia rheumatica with high sensitivity and specificity. EJNMMI. 2020;47(10):2461-8). Participants will complete a standardised symptom and treatment diary at monthly intervals over the 6-month follow-up period. At 24 weeks post enrolment, a final study visit will be undertaken at Heidelberg Repatriation Hospital (visit duration 30 minutes). This shall comprise the same assessments carried out at baseline and repeat laboratory testing (FBE, UEC, LFTs, CRP, ESR and “Predicting Autoimmunity” samples for novel biomarker testing if opted in). The participant’s final clinical diagnosis will be determined by the treating rheumatologist.