[18F]fluorodeoxyglucose uptake as a predictor of large joint destruction in patients with rheumatoid arthritis

The present retrospective study investigated the relationship between [(18)F]fluorodeoxyglucose-positron emission tomography (FDG-PET) findings and subsequent progression of joint destruction on plain X-ray. Nineteen rheumatoid arthritis (RA) patients (59 joints) who underwent FDG-PET and whose joints could be evaluated on plain X-ray 5 years later were included in this retrospective investigation. The relationship between the standardized uptake value (SUV) on FDG-PET and Larsen grade progression on plain X-ray was investigated for each joint. Factors related to progression of joint destruction were also investigated. Joints with advanced joint destruction (Larsen grades IV and V) on X-ray imaging at the time of FDG-PET were excluded. On initial plain X-ray images taken at the time of FDG-PET, a significant correlation was observed between the initial SUV of each joint and the progression of joint destruction 5 years later (R = 0.47, P < 0.01). Significant correlations between the SUV and progression of joint destruction were observed in both load-bearing (R = 0.52, P < 0.01) and non-load-bearing joints (R = 0.52, P < 0.01). On logistic regression analysis, higher SUV and lower prednisolone dose were associated with greater risk of progressive joint destruction (P < 0.05). On receiver operating characteristics curve analysis, the optimum threshold for identifying preceding joint destruction was an SUVmean of 1.33. In RA joints, FDG uptake was seen mostly by inflammatory cells; therefore, FDG uptake reflected joint inflammation. Additionally, the activity seen on FDG-PET might be associated with future radiographic changes in RA patients.