Ultrasound-detectable grey scale synovitis predicts future fulfilment of the 2010 ACR/EULAR RA classification criteria in patients with new-onset undifferentiated arthritis

OBJECTIVE: To determine the clinical outcomes for patients with new-onset undifferentiated arthritis (UA), not fulfilling the 2010 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) rheumatoid arthritis (RA) classification criteria, and the clinical and imaging predictors of disease progression in these patients. METHODS: A prospective observational study was conducted in treatment-naïve UA patients. Baseline ultrasound involved semiquantitative assessment of grey scale (GS) synovitis and power Doppler activity (PD) at 26 joints. Outcomes were fulfilment of 2010 RA criteria (joint involvement determined clinically) and initiation of methotrexate over 12 months. Cox proportional hazards analysis was used to investigate predictors of outcome. RESULTS: Of 60 patients, 13(22%) progressed to RA and 32(53%) ever received methotrexate. Analyses of predictors of outcome were conducted in the subgroup (n=41) of patients with complete baseline data. The presence of GS was associated with progression to RA and methotrexate use: HRs (95% CI) were 1.25(1.07 to 1.45) and 1.16(1.02 to 1.32), respectively, for the number of joints with GS≥ grade 2 after adjustment for swollen joints. PD was not predictive in the low levels at which it was observed. Progression to RA was also associated with fulfilment of the 2010 criteria using ultrasound synovitis for enumerating joint involvement, higher baseline disability and radiographic erosion. CONCLUSIONS: This is the first report of ultrasound findings in early UA (defined by presence of clinical synovitis and non-fulfilment of 2010 RA criteria). A significant proportion of patients with UA progressed to RA and/or required methotrexate. GS synovitis was predictive of disease progression.