In an obese rheumatoid arthritis (RA) patient, a clinically assessed swollen joint (SJ) diagnosis is less likely to represent true synovitis, as measured by power Doppler (PDUS), according to a recent study. Disease activity in obese RA patients may be overestimated by clinical disease activity index (CDAI)/Disease Activity Score (DAS28) calculations and clinicians when considering change in therapy. Cross-sectional clinical and laboratory data were collected on 43 RA patients. PDUS was performed on 9 joints; DAS28 and CDAI were calculated. Patients were categorized by BMI: <25, 25–30, and >30. Researchers found:

• While demographics and clinically-determined disease activity were similar among BMI groups, PDUS scores significantly differed.
• Using PDUS activity as the reference standard for synovitis and clinically SJ as the test, the positive predictive value of SJ was significantly lower in higher BMI groups (0.71 in BMI < 25, 0.58 in BMI 25–30, and 0.44 in BMI < 30).