Background It has been reported that 18FDG-PET (PET) is useful in the evaluation of RA and for monitoring the effects of treatment on the disease activity, so its utility for the evaluation of arthritis is expected. However, the mechanism underlying the uptake of FDG into the inflamed joint is still unclear.
Objectives The aim of this study was to investigate the associations among the amount of FDG uptake in RA joints, the inflammatory findings with regard to the pathology of the synovium and the clinical findings.
Methods We performed PET in 18 RA patients who underwent Total Knee Arthroplasty surgery in our hospital just prior to surgery. We calculated the FDG uptake as the standardized uptake value (SUV)max and scored it using the Rooney score, with the degree of inflammation of the synovial tissues used for the pathological evaluation. We evaluated the associations among the SUVmax, Rooney score, CRP level, ESR and MMP-3 level just before surgery.
Results The subjects were 18 cases with 20 joints, which were in four females and 14 males. At the time of surgery, the average age of the patients was 66.7±7.9 years old, and the mean disease duration was 20.8±14.0 years. Significant correlation was not observed between SUVmax and total Rooney score (r =0.056, p=0.814). But there were strong correlations between SUVmax and some of the individual items in Rooney score, including the “Synoviocyte hyperplasia”, and also between SUV max and “Diffuse infiltrates of lymphocytes” (r=0.512, p=0.021 and r=0.581, p=0.007, respectively).
Conclusions The accumulation of FDG was associated with the extent of “synoviocyte hyperplasia” and “diffuse infiltrates of lymphocytes”. It is estimated that accumulation of FDG is associated with relatively early stage of active inflammation of RA.
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Disclosure of Interest None declared