Ultrasonography (US) In a systematic literature search up to 2009 [1], no US publications on pure undifferentiated populations and only 2 publications in mixed populations (not optimal) [2,3] were available. In the seronegative (RF and anti-CCP negative) subgroup of 50 early undifferentiated inflammatory arthritis patients, certain clinical and radiographic features (elevated CRP, swollen joints and radiographic erosion) raised the probability of persistent inflammatory arthritis from 6-30%, whereas further addition of 1-3 specific US features (grade 3 grey scale synovial hypertrophy, at least grade 2 synovial power Doppler signal and at least one erosion) further increased the probability, suggesting that combining US evaluation with routine assessment in seronegative early arthritis may markedly increase the certainty of diagnosis [3]. In seropositive disease (RF and/or anti-CCP positive), US had no predictive value.

A subsequent study of undifferentiated arthritis patients reported, based on regression analyses, that greyscale wrist and MCP joint involvement, and power Doppler MTP joint involvement had independent predictive value for subsequent development of rheumatoid arthritis (RA) according to the ACR 1987 criteria [4].

Magnetic resonance imaging (MRI) A systematic literature review up to 2009 found 2 relevant articles in pure undifferentiated populations [5,6] and 9 articles [7–15] on mixed (mixed undifferentiated and diagnosed patients; less optimal) populations [1]. The conclusion of the SLR was that MRI bone edema and the combined synovitis and erosion pattern seem useful in predicting development of RA from UPIA, but that additional studies were needed.

In the 2 studies in pure undifferentiated arthritis, one showed that the combined synovitis and erosion pattern was related to development of RA or not [5], whereas the other demonstrated that presence of bone edema had a positive predictive value of 86.1% for subsequent development of RA according to the ACR 1987 criteria [6].

After the SLR, a large follow-up study of undifferentiated arthritis documented MRI as predictor of the diagnosis of RA [16]. In 116 undifferentiated patients bone edema in wrist and MTP joints was an independent predictor of subsequent development of RA according to the ACR 1987 criteria. A prediction model, including clinical hand arthritis, morning stiffness, positive RF and MRI bone edema score in MTP and wrist joints correctly identified the development of RA or non-RA in 82% of patients [16].

ACR/EULAR 2010 criteria In 2010 MRI and US has been incorporated in international criteria for RA. The older ACR 1987 criteria for RA were not very sensitive in early RA, and with the aim to improve performance in early disease, newly developed classification criteria for RA were published in 2010 [17]. In these recent ACR/EULAR 2010 criteria for RA, classification as definite RA is based on presence of definite clinical synovitis (swelling at clinical examination) in ≥1 joint, absence of an alternative diagnosis that better explains the synovitis, and achievement of a total score ≥6 (of a possible 10) from the individual scores in 4 domains. In the joint involvement domain, which can provide up to 5 points of the 6 needed for an RA diagnosis, MRI and US synovitis count. In other words, MRI and US can be used to determine the joint involvement [17–19]. The fact that MRI and US are now officially accepted for this purpose by the European and American rheumatological communities is an important step in the recognition of the utility of MRI and US in the diagnosis and management of inflammatory arthritides.

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Disclosure of Interest None declared

DOI 10.1136/annrheumdis-2014-eular.6334