Background: MRI-detected subclinical joint inflammation in the hand joints of patients with undifferentiated\narthritis (UA) predicts progression to rheumatoid arthritis (RA). It is unknown if adding MRI of the foot increases\npredictive accuracy compared to the hand alone.\nMethods: 1.5-T contrast-enhanced MRI of the unilateral foot (MTP-1-5) and hand (MCP-2-5 and wrist) was\nperformed in 123 patients presenting with UA (not fulfilling the 2010 RA criteria) and scored for bone\nmarrow edema (BME), synovitis and tenosynovitis. Symptom-free controls (n = 193) served as a reference for\ndefining an abnormal MRI. Patients were followed for RA development greater than or equal to, defined as fulfilling the\nclassification criteria or initiation of disease-modifying antirheumatic drugs because of the expert opinion of\nRA. The added predictive value of foot MRI to hand MRI was evaluated.\nResults: Fifty-two percent developed RA. Foot tenosynovitis was predictive (OR 2.55, 95% CI 1.01-6.43), independent of\nBME and synovitis (OR 3.29, 95% CI 1.03-10.53), but not independent of CRP and number of swollen joints (OR 2.14, 95%\nCI 0.77-5.95). Hand tenosynovitis was also predictive independent of BME and synovitis (OR 3.99, 95% CI 1.64-9.69) and\nindependent of CRP and swollen joints (OR 2.36, 95% CI 1.04-5.38). Adding foot tenosynovitis to hand tenosynovitis\nchanged the sensitivity from 72 to 73%, specificity from 59 to 54% and AUC from 0.66 to 0.64; the net reclassification\nindex was-3.5.\nConclusion: MRI-detected tenosynovitis of the foot predicts progression to RA. However, adding MRI of the foot does\nnot improve the predictive accuracy compared to MRI of the hand alone. In view of cost reduction, the performance of\nfoot MRI for prognostic purposes in UA can be omitted.
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