Objectives To analyse whether ACR/EULAR negative early undifferentiated arthritis patients have a different course of the disease dependent on whether they can or cannot be classified as RA because of radiographic disease (as recently defined by the EULAR task force) at diagnosis.
Methods For this observational study within the Swiss RA cohort SCQM, we included patients with early undifferentiated arthritis (disease duration ≤1 year), as diagnosed by the treating rheumatologist, who had not received any previous DMARDs. 2010 ACR/EULAR criteria negative patients were separated into 2 groups (radiographic vs. non radiographic arthritis) depending on whether or not they had radiographic changes recently defined as erosive disease by a EULAR task force (≥3 erosions). The effect of a positive Erosion score (was analysed for DAS-28 and HAQ scores using linear mixed models with random slope and random intercept, and adjusted for various baseline factors in a univariate fashion. Slopes of the Ratingen score after diagnosis were compared between groups using analysis of variance (ANOVA). The primary outcome measure was the radiographic progression detected employing the Ratingen erosion score. HAQ and DAS 28 were used as secondary outcome measures. The average observation period was 4 years.
Results A total number 592 patients was analysed. 240 were not classifiable as RA by application of the 2010 ACR/EULAR criteria at baseline. 133 of these patients had radiographic arthritis and 50 non-radiographic arthritis. In 57 patients radiographs at the first visit were not available. Treatment was initiated in all patients with DMARDs, mostly MTX. There were no significant differences in the therapeutic strategies between radiographic and non-radiographic patients. No differences in DAS 28 and HAQ scores were found during follow up over 4 years. The average erosion scores were higher among patients with initially radiographic arthritis throughout the study. The progression of erosion scores over time, however, was higher in initially non radiographic arthritis patients (3.3 erosions/year vs. 0.4, resp., p<0.0001).
Conclusions The clinical and radiographic progression of early undifferentiated arthritis under treatment was not dependent on the presence of 3 or more erosions (i.e. the definition of radiographic disease by the EULAR taskforce) at diagnosis in our cohort.
Disclosure of Interest None declared