The value of magnetic resonance imaging for assessing disease extent and prediction of relapse in early peripheral spondyloarthritis.

OBJECTIVE We aimed to assess the inflammatory burden in pSpA by lower-extremity MRI in an early remission-induction strategy study with TNF blockade. Furthermore, we sought to determine the value of MRI to predict disease relapse versus sustained remission after treatment discontinuation. METHODS Thirty-two early pSpA patients with lower limb involvement on clinical examination and confirmed by ultrasonography, participated in a remission-induction trial with a TNF-inhibitor (TNFi). Patients underwent MRI of joints and entheses of the lower extremities at baseline and at clinical remission, after which TNFi treatment was withdrawn. Images were evaluated for joint effusion, joint osteitis, entheseal soft tissue inflammation (STI), and entheseal osteitis. RESULTS Joint effusion and enthesitis on clinical examination and ultrasonography correlated well with MRI abnormalities. In addition, a substantial amount of subclinical involvement was seen on MRI, mainly in ankle joints and heel entheses. Inflammation scores were markedly lower in the subclinical joints and entheses versus those clinically involved. Inflammatory load on MRI decreased significantly upon TNFi treatment. Whereas 80% of the clinically involved joints at baseline showed no effusion on remission MRI, two out of three involved entheses at baseline showed residual inflammation. In addition, patients relapsing after treatment discontinuation displayed more entheseal STI on remission MRI compared to those maintaining drug-free remission. CONCLUSION Our findings delineate a differential response of synovitis and enthesitis, with enthesitis on MRI responding less upon TNFi treatment. Furthermore, residual entheseal inflammation might be indicative for the need for continuous therapy.