Polymyalgia rheumatica (PMR) is an inflammatory disorder primarily characterized by pain and stiffness in the shoulder and hip girdle regions. It commonly affects individuals over the age of 50, with women accounting for approximately 75 % of cases. The incidence of PMR peaks between the ages of 70 and 80 [1,2]. Traditionally, diagnosis relies heavily on clinical presentation and laboratory findings. In 2012, American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) published the latest provisional classification criteria for PMR [3], which incorporated ultrasound examination. While these methods are somewhat effective, they often suffer from limited sensitivity and specificity. Additionally, the operator-dependent nature and limitations of ultrasound examinations present challenges for early diagnosis.

In recent years, [18F] Fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) has emerged as a powerful imaging technique for evaluating inflammatory arthritis in rheumatic diseases [4], particularly in the diagnosis of PMR. A recent meta-analysis showed that PET/CT significantly enhances the diagnostic accuracy for PMR [5]. In a previous study conducted at our center [6], we found that the sensitivity of using the SUV index to diagnose PMR at characteristic sites was 84.6 %, with a specificity of 92.6 %. Furthermore, when the SUV index reached≥1.685, the likelihood of diagnosing PMR increased significantly. Studies have shown that fluorodeoxyglucose (FDG) uptake in PET/CT is most pronounced in the shoulder and hip joints, surrounding regions, and interspinous bursa, among other joint areas [7]. Based on this, various PET/CT scoring systems for PMR have been developed, with the Leuven scoring system exhibiting the highest diagnostic performance [8]. However, its requirement to assess multiple joints can be cumbersome, posing challenges in clinical practice. A study comparing the diagnostic performance of different PET/CT scoring systems proposed a simplified version of the Leuven score, which maintained diagnostic accuracy similar to the original [9]. While other groups have introduced scoring systems based on simplified algorithms, such as the Saint-Étienne, Heidelberg, and Copenhagen scores [[10], [11], [12]], these systems assess FDG uptake in only a few anatomical sites, resulting in further reductions in sensitivity and specificity. It is important to note that, in clinical practice, rheumatologists typically do not rely solely on PET/CT findings to diagnose PMR. Instead, they combine PET/CT results with clinical features. In a recent study [13], Nielsen A.W. et al. were the first to integrate the Leuven score with the ACR/EULAR clinical classification criteria, achieving a sensitivity of 80 % and specificity of 93 %. However, simply combining the Leuven score with the 2012 ACR/EULAR classification criteria is somewhat rigid. Currently, there is a preference for using more simplified PET/CT scoring systems. Based on this, the aim of this study is to develop a new simplified comprehensive scoring system using data from our center, which combines PET/CT results with clinical features. The goal is to improve its applicability in clinical settings and further enhance both the diagnostic specificity and sensitivity for polymyalgia rheumatica. Additionally, we are validating the diagnostic performance of the new scoring system in a validation cohort.