Relapse Rate After Glucocorticoid-Free Remission in Patients With Idiopathic Inflammatory Myopathies and Validation of the International Myositis Assessment and Clinical Studies Group Criteria for Complete Clinical Response and Worsening.

Abstract

Our aim was to explore maintenance of glucocorticoid-free remission in patients with idiopathic inflammatory myopathy (IIM). Additionally, we examined the performance of the International Myositis Assessment and Clinical Study Group (IMACS) criteria for complete clinical response and flare/worsening. Patients achieving physician-determined glucocorticoid-free remission were extracted from the Swedish Rheumatology Quality Register (SRQ). Relapse rates and associated factors were analyzed. To assess the performance of complete clinical response criteria, IMACS core set measures were evaluated within six months before and after remission. Relapse was defined as IMACS criteria of worsening in IMACS core set measures over 20% to 30% during every visit or in the period from remission to a time point with worsening (modified definition) or glucocorticoid/immunosuppressant administration. Changes from remission to all subsequent visits were compared. The visit with the largest change was chosen as the worse time point (modified definition). Of 494 patients, 159 (32%) achieved physician-determined glucocorticoid-free remission. The 12-year cumulative relapse rate was 76%, with anti-Jo1 as a risk factor. From time of remission to six months after remission, IMACS complete clinical response fulfillment rates were as follows: creatine kinase, 23%; Health Assessment Questionnaire, 50%; patient global assessment, 70%; physician global assessment, 80%; extramuscular activity, 83%; and Manual Muscle Test 8, 95%. Only 50% of relapses could be captured by the IMACS worsening definition, but additional relapses were captured by a modified IMACS worsening definition (15%) or by reintroduction of glucocorticoid/immunosuppressant treatment (35%). Relapses were frequent in patients with IIM after achieving glucocorticoid-free remission and required management of therapy. IMACS criteria for complete clinical response/worsening need to be amended.