For a study, researchers sought to find out if early rheumatoid arthritis (RA) patients may have whole-body positron emission tomography/computed tomography (PET/CT) with a macrophage tracer to scan their RA.

In addition to clinical assessment (Disease Activity Score in 44 joints [DAS44]), 35 clinically active early RA patients who were previously untreated received whole-body PET/CT scanning with the macrophage tracer (R)-[11C]PK11195. Tracer uptake was quantified and evaluated using standardized uptake values (SUVs). Additionally, 2 readers who were blind to the clinical evaluation graded the joints’ tracer uptake visually. Where appropriate, clinical and PET variables were compared using Cohen, linear regression/correlation, and t tests.

All patients except 1 had increased tracer uptake in at least one joint. The PET scan revealed visible signs of 12% of all joints (171/1470), most often the tiny joints in the foot (40%) and hands (37%), then the wrists (15%). There were no or weak correlations between visual scores and clinical data at the patient and joint levels. The strongest association was seen in the feet (R2=0.29, P<0.01), whereas average SUVs in the hands, feet, and entire body had significant relationships with DAS44 scores.

Patients with early RA who were clinically active showed higher joint absorption of a macrophage PET tracer, particularly in the foot. In addition, the complete body and joint groups, especially the feet, demonstrated quantitative but not visual PET measurements of moderately and statistically significant relationships with clinical outcomes.