BMI and Ultrasound/Clinical Assessments of RA Disease Activity (RABODI)

Clinical evaluation of synovitis in rheumatoid arthritis (RA) is difficult in obese and overweighted patients, due to the fat pad located around the joint, that can over- or under estimate the number of joints regarded as swollen by clinical examination. RA in obese and overweighted patients has several distinctive characteristics as compared to the disease observed in normally weighted subjects: diease activity (assessed by composites scores such as Disease Activity Score (DAS28) or Simple Disease Activity Index (SDAI)) is higher, while response to treatment and severity (asessed by radiographic progression) are lower.

Objectives:

Primary end point: Comparison of the level of agreement between the number of joints considered abnormal by Power Doppler ultrasound synovitis (≥ grade 1 on a semi-quantitative scale) and clinical examination (swollen joint count (SJC) as componant of SDAI) in obese (i.e. BMI\>30) versus normally weighted RA patients.

Secondary end points :

* Comparison of the level of agreement between clinical and ultrasound findings in overweighted versus normally weighted patients, when joint count evaluation is based on another composite index ((DAS28-CRP et DAS44-CRP), based on the number of tender joints, and based on a joint by joint evaluation * Comparison of agreement between obese and non obese * Evaluation of the impact of other factors than BMI on the level of agreement between Power Doppler ultrasound defined number of synovitis and clinically defined swollen joint count * Reliability between Ultrasound and clinical examination across the different investigation centers Study design: prospective multicenter observational study Inclusion criteria: RA patients fulfilling ACR/EULAR 2010 criteria Exclusion criteria: patient simultaneously included in another study with blinded treatment; Steinbrocker class IV patients Outcome measure : Level of agreement between SJC and power Doppler US synovitis