Background and Objectives Several biological therapies have become available in the last years in the management of rheumatoid arthritis (RA). Two of the most common drug classes include anti-tumour necrosis factor (TNF) and anti-interleukin-6 (IL-6) agents, which target central cytokines in the disease pathway. We have previously shown that the proportion of patients achieving remission was higher in the tocilizumab group, an anti-IL-6 agent, compared to anti-TNF therapies, but the magnitude of the effect was associated with the disease activity measure used, namely DAS28, CDAI or SDAI. The aim of this study is to assess whether this difference remains significant in other RA disease activity states.
Materials and Methods We included biologic-naïve RA patients registered in the Rheumatic Diseases Portuguese Register, Reuma.pt, who have started therapy with anti-TNF (adalimumab, infliximab, golimumab) and anti-IL-6 (tocilizumab) monoclonal antibodies after 1st January 2008. Our primary outcome was the proportion of patients in each disease activity state (remission, low, moderate, high) at 6 months, applying DAS28, CDAI and SDAI. Univariate and multivariate logistic regressions were performed to compare the groups.
Results 220 RA patients were enrolled, 180 treated with anti-TNF monoclonal antibodies and 40 treated with tocilizumab. Both groups had similar baseline characteristics but tocilizumab-treated patients had significantly higher SJC, DAS28, SDAI and CDAI as well as shorter disease duration. At 6 months, a significantly higher proportion of patients in the tocilizumab group had reached the DAS28 (n = 21, OR 0.16, p < 0.0001, 95%CI 0.06–0.38) and SDAI (n = 9, OR 0.29, p = 0.03, 95%CI 0.09–0.91) remission thresholds, but no significant difference was seen for CDAI (n = 8, OR 0.41, p = 0.12), in the adjusted logistic multivariate model. Moreover, the proportion of patients with moderate (n = 85, OR 3.49, p = 0.006, 95%CI 1.44–8.43) and high disease activity (n = 30, OR 6.13, p = 0.028, 95%CI 1.32–30.89) was higher in the anti-TNF group only according to DAS28. No differences were seen in the low disease activity class.
Conclusions Globally, tocilizumab-treated patients had better disease activity outcomes, but the magnitude of the effect was dependent on the disease activity measure used, confirming our previous results and underlining the pronounced reduction of inflammatory markers such as ESR and CRP, translated by lower DAS28 and SDAI, respectively. Furthermore, this effect was also related to the disease activity state considered. This may be explained by the fact that these different indexes distinctly weigh the different components and/or do not classify the same patients in the same disease activity state.
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