The value of magnetic resonance imaging and ultrasound in undifferentiated arthritis: a systematic review.

OBJECTIVE: To perform a systematic literature review of the diagnostic and prognostic value of magnetic resonance imaging (MRI) and ultrasound (US) in patients with undifferentiated peripheral inflammatory arthritis (UPIA), and to assess if MRI and US should be done at baseline and repeated, and if so, at what interval.
METHODS: Medline, Embase, the Cochrane Library, and abstracts presented at the 2007 and 2008 meetings of the American College of Rheumatology and European League Against Rheumatism meetings were searched for diagnostic and prognostic studies of any duration examining the ability of MRI/US to predict outcome of patients with UPIA. Sensitivity, specificity, predictive values, and positive/negative likelihood ratios (LR+/LR-) were calculated. When available, odds ratios were extracted. Quality was appraised using validated scales.
RESULTS: Regarding MRI, 11 out of 2595 screened references were included: 2 described pure undifferentiated arthritis (UA) populations and 9, mixed populations. Bone edema (LR+ 4.5) and combination of a distinct MRI synovitis and erosion pattern (LR+ 4.8) increased probability of developing rheumatoid arthritis (RA). Absence of MRI synovitis (LR- 0.2) and absence of a distinct synovitis pattern (LR- 0) decreased probability of developing RA. Regarding US, 2 out of 2111 references were included, both mixed populations; no data could be extrapolated for UPIA.
CONCLUSION: MRI bone edema and combined synovitis and erosion pattern seem useful in predicting development of RA from UPIA. The value of US in UPIA remains to be determined. The absence of MRI synovitis seems useful in excluding development of RA. No data were found about the value of repeating MRI/US. Studies evaluating MRI/US in UPIA are scarce, but current knowledge strongly encourages further testing in UA.