Serum soluble interleukin-2 receptor predicts early remission in patients with recent-onset rheumatoid arthritis treated with a single disease-modifying antirheumatic drug.

Objective. To study the value of baseline serum levels of circulating soluble interleukin-2 receptor (sIL-2R) and soluble E-selectin as predictors of early remission in patients with recent-onset rheumatoid arthritis (RA) receiving a single disease-modifying antirheumatic drug (DMARD) (SINGLE) or therapy with a combination of DMARDs (COMBI). Methods. Baseline (n= 157) serum samples originate from the FIN-RACO (FINnish Rheumatoid Arthritis Combination therapy) trial, in which 195 patients with early and clinically active RA were randomly assigned to receive either SINGLE (initially sulfasalazine) with or without prednisolone, or COMBI therapy (sulfasalazine, methotrexate, hydroxychloroquine, and prednisolone). Of the samples, 76 were from SINGLE patients and 81 from COMBI patients. sIL-2R was measured by automated immunoassay analyzer and sE-selectin by enzyme-linked immunosorbent assay. Results. At six months, 7 (9% [95% CI: 4 to 18]) SINGLE and 19 (23% [95% CI: 15 to 34]) COMBI patients were in remission. In multivariate logistic regression analysis, sIL-2R <442 U/ml and COMBI therapy were the only predictors of remission. The area under receiver operating characteristic curve for sIL-2R level was 0.86 (95% CI: 0.62 to 0.95) in SINGLE and 0.57 (95% CI: 0.42 to 0.71) in COMBI (p = 0.006). In SINGLE, the optimal cut off-point was 442 U/ml, lower levels predicting remission with sensitivity of 83% (95% CI: 73% to 91%) and specificity of 86% (95% CI: 42% to 100%). Likelihood ratio for positive test was 5.9 (95% CI: 1.6 to 32.8). In multivariate logistic regression analysis, sIL-2R <442 U/ml and COMBI therapy were the only predictors of remission. Conclusion. Low baseline serum sIL-2R level predicts early remission of patients with active early RA treated with a single DMARD.