OBJECTIVES: Identifying patients that will develop RA among those presenting with undifferentiated arthritis (UA) remains a clinical dilemma. Although MRI is helpful according to EULAR recommendations, this has only been determined in UA patients not fulfilling 1987 RA criteria, while some of these patients are currently considered as RA because they fulfil the 2010 criteria. Therefore, we studied the predictive value of MRI for progression to RA in the current UA population, i.e. not fulfilling RA classification criteria (either 1987 or 2010 criteria) and not having an alternate diagnosis. Additionally, the value of MRI was studied in patients with a clinical diagnosis of UA, regardless of the classification criteria. METHODS: Two UA populations were studied: criteria-based UA as described above (n = 405) and expert-opinion-based UA (n = 564), i.e. UA indicated by treating rheumatologists. These patients were retrieved from a large cohort of consecutively included early arthritis patients that underwent contrast-enhanced MRI scans of hand and foot at baseline. MRIs were scored for osteitis, synovitis and tenosynovitis. Patients were followed for RA development during the course of 1 year. Test characteristics of MRI were determined separately for subgroups based on joint involvement and autoantibody status. RESULTS: Among criteria-based UA patients (n = 405), 21% developed RA. MRI-detected synovitis and MRI-detected tenosynovitis were predictive for progression to RA. MRI-detected tenosynovitis was independently associated with RA progression (odds ratio (OR) 2.79; 95% CI 1.40, 5.58), especially within ACPA-negative UA patients (OR 2.91; 95% CI 1.42, 5.96). Prior risks of RA development for UA patients with mono-, oligo- and polyarthritis were 3%, 19% and 46%, respectively. MRI results changed this risk most within the oligoarthritis subgroup: positive predictive value was 27% and negative predictive value 93%. Similar results were found in expert-opinion-based UA (n = 564). CONCLUSION: This large cohort study showed that MRI is most valuable in ACPA-negative UA patients with oligoarthritis; a negative MRI could aid in preventing overtreatment.
The research leading to these results has
received funding from the Dutch Arthritis Foundation
and the European Research Council (ERC) under the
European Union’s Horizon 2020 research and innovation
program (starting grant, agreement No. 714312). The
funding source had no role in the design and conduct of
the study; collection, management, analysis and interpretation of the data; preparation, review or approval of
the manuscript; or decision to submit the manuscript for
© The Author(s) 2022. Published by Oxford University Press on behalf of the British Society for Rheumatology.