Systematic review of imaging tests to predict the development of rheumatoid arthritis in people with unclassified arthritis
Authors: de Pablo P , Dinnes J , Berhane S , Osman A , Lim Z , Coombe A , Raza K , Filer A , Deeks JJ 
Published: March 2021

AbstractObjectivesTo estimate and compare the diagnostic accuracy of magnetic resonance imaging (MRI) and ultrasound, for the prediction of rheumatoid arthritis (RA) in unclassified arthritis (UA).MethodsMEDLINE, Embase and BIOSIS were searched from 1987 to May 2019. Studies evaluating any imaging test in participants with UA were eligible. Reference standards were RA classification criteria or methotrexate initiation. Two authors independently extracted data and assessed validity using QUADAS-2. Sensitivities and specificities were calculated for each imaging characteristic and joint area. Summary estimates with 95% confidence intervals (CI) were estimated where possible.ResultsNineteen studies were included; 13 evaluated MRI (n=1,143; 454 with RA) and 6 evaluated ultrasound (n=531; 205 with RA). Studies were limited by unclear recruitment procedures, inclusion of patients with RA at baseline, differential verification, lack of blinding and consensus grading. Study heterogeneity largely precluded meta-analysis, however summary sensitivity and specificity for MRI synovitis in at least one joint were 93% (95% CI 88%, 96%) and 25% (95% CI 13%, 41%) (3 studies). Specificities may be higher for other MRI characteristics but data are limited. Ultrasound results were difficult to synthesise due to different diagnostic thresholds and reference standards.ConclusionsThe evidence for MRI or ultrasound as single tests for predicting RA in people with UA is heterogeneous and of variable methodological quality. Larger studies using consensus grading and consistently defined RA diagnosis are needed to identify whether combinations of imaging characteristics, either alone or in combination with other clinical findings, can better predict RA in this population.Systematic review registrationPROSPERO CRD42020158239.Key messagesTo date, the diagnostic accuracy of imaging tests for the earlier identification of RA has not been systematically assessed. We conducted a systematic review to estimate, and if possible compare, the accuracy of MRI and ultrasound for predicting the diagnosis of rheumatoid arthritis in people with unclassified arthritis.In this systematic review of 13 studies of MRI (1,143 participants) and 6 studies of ultrasound (531 participants), study quality was highly variable with considerable variation in populations, diagnostic thresholds and reference standards limiting potential for meta-analysis.Individual MRI imaging characteristics demonstrated either high sensitivity (with low specificity) or high specificity (with low sensitivity) with inconsistent results between studies. Similar heterogeneity in results was observed for ultrasound but with considerably fewer data.Imaging can identify subclinical inflammatory changes in joint areas where no synovitis is apparent, which may be useful in identifying the aetiology of symptoms. However, larger studies using consistent scoring systems for imaging interpretation and definition of RA are needed to identify the extent to which imaging findings alone can predict the development of RA. Until then, imaging should be interpreted in light of other findings.