Overweight and obesity affect clinical assessment of synovitis in rheumatoid arthritis: comparison of ultrasonography and clinical exam.

OBJECTIVE

Body mass index (BMI) might affect rheumatoid arthritis (RA) outcomes. Clinical assessment of swollen joint count (SJC) might also be affected by obesity in terms of obesity-related excess adipose tissue. In this study, we compared ultrasonography (US) and clinical examination in assessing the effect of BMI on RA disease activity assessment.

METHODS

This was a single-centre study including RA (ACR/EULAR criteria) patients. US assessment was performed by one trained rheumatologist blinded to clinical data. US synovitis was defined as grey-scale score ≥2 and/or power Doppler score ≥1. The primary outcome measure was difference in SJC (ΔSJC) between clinical and US assessment (US-clinical examination). The secondary outcome was to evaluate the difference between clinical and US assessment of the Disease Activity Score in 28 joints (ΔDAS28) in the 3 BMI subgroups according to the WHO classification.

RESULTS

We included 76 RA patients (mean age 53.8 ± 11.8 years; 67% female). Overall, 28 (36.8%), 33 (43.4%) and 15 (19.7%) were normal weight, overweight and obese, respectively. Baseline characteristics did not differ between the 3 BMI subgroups. US-determined SJC was significantly higher than clinical-determined SJC for overweight and obese RA patients: p=0.001 and p=0.049, respectively. The DAS28 was higher with US than clinical examination within the overweight group only (p=0.002). One-way analysis of variance (ANOVA) revealed a significant difference between ΔDAS28 among the 3 BMI subgroups (p=0.046).

CONCLUSIONS

In high BMI RA patients both SJC and DAS28 seem to be undervalued by clinical assessment when compared to US.