%0 Journal Article %A Uri Arad %A Ori Elkayam %T Association of serum Tocilizumab trough concentrations with clinical disease activity index scores in adult rheumatoid arthritis patients. %D 2019 %R 10.3899/jrheum.181431 %J The Journal of Rheumatology %P jrheum.181431 %X Objective To determine whether serum trough concentrations of tocilizumab (TCZ) administered as a fixed dose subcutaneous injection for the treatment of rheumatoid arthritis (RA), are associated with disease activity responses. Methods We analyzed data sets from the Israeli branch of the multinational TOZURA study, which evaluated a weekly subcutaneous TCZ treatment regimen in a real-life clinical setting. Generalized estimating equations (GEE) were used to evaluate associations between the TCZ levels and the study outcomes. Linear models and GEE were used to evaluate associations between patients characteristics and TCZ levels. Results A significant association between the TCZ concentrations and the change in the CDAI score was observed. In a multivariate binary GEE model, every increase of 10 g/ml in the concentration of TCZ was associated with an odds ratio of 1.41 of being in a state of CDAI remission or low disease activity versus moderate/high disease activity state, and with an odds ratio of 1.52 of being in a state of HAQ-DI remission. In univariate linear models, there was an inverse association between BMI and improvement in the CDAI score and the BMI score was associated with lower TCZ concentrations. Patients that weighed more than 100 kg had lower TCZ concentrations. Conclusion In the first 24 weeks of treatment with SC TCZ injections, TCZ concentrations are associated with clinical improvement, while body weight and BMI are inversely associated with TCZ concentrations. Personalizing the dose of SC TCZ to body weight may improve outcomes of clinical disease activity in RA patients. %U https://www.jrheum.org/content/jrheum/early/2019/05/24/jrheum.181431.full.pdf