The following is a summary of  “Articular 18Fluorodeoxyglucose Uptake Is Associated With Clinically Assessed Swollen Joint Count in Patients With Rheumatoid Arthritis” published in the December 2022  issue of  Rheumatology by Ferraz-Amaro et, al.

The disease activity of rheumatoid arthritis (RA) cannot be accurately assessed with traditional examination and radiographic imaging of the joints. Researchers used  18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) to quantify joint inflammation in RA patients to ascertain whether or not PET-derived uptake factors were connected with RA disease activity markers. In a substudy of the Rheumatoid Arthritis Study of the Myocardium, researchers conducted cross-sectional studies on 34 individuals with RA (RHYTHM). 

To compensate for attenuation and anatomically co-register the Positron emission tomography (PET) of 18F-FDG in all patients, CT scans were performed. Articular FDG uptake, expressed as standardized uptake values(SUVs), was modeled using linear regression to examine relationships between disease activity ratings and uptake (SUVs). As global variables of the total volume of joint inflammation in each patient, researchers derived weighted joint volume SUVs (wjSUVs) at 25%, 50%, 75%, and maximal (100%) uptake. Statistics showed a strong correlation between the number of swollen joints and the calculated wj25SUV (Spearman ρ=0.39, P=0.04), wj50SUV (ρ =0.39, P=0.04), and wj75SUV (ρ=0.37, P=0.045).

Simplified Disease Activity Index showed similar substantial relationships with 28 joints, although Clinical Disease Activity and Disease Activity Score did not. Articular FDG uptake was not linked to any RA-related factors outside of the joints (i.e., disease duration, seropositivity, or RA treatments). Although biochemical indicators of inflammation were not substantially linked with articular FDG absorption in RA patients, the number of swollen joints did.