Assessment of the validity of the 28-joint disease activity score using erythrocyte sedimentation rate (DAS28-ESR) as a disease activity index of rheumatoid arthritis in the efficacy evaluation of 24-week treatment with tocilizumab: subanalysis of the SATORI study

As tocilizumab (TCZ) greatly inhibits inflammatory markers, methods of evaluating rheumatoid arthritis (RA) disease activity that include inflammatory markers may overestimate the effect of TCZ treatment. We have evaluated the impact of inflammatory markers on the efficacy of TCZ by comparing the efficacy indicated by the 28-joint disease activity score using erythrocyte sedimentation rate (DAS28-ESR) with that indicated by the clinical and simplified disease activity indexes (CDAI and SDAI, respectively) and the American College of Rheumatology (ACR) core set criteria in a double-blind study of TCZ-the SATORI study. The Spearman correlation coefficient between DAS28-ESR and CDAI was comparable between that at week 24 and that at baseline [correlation coefficient at baseline and week 24 was 0.823 (p < 0.0001) and 0.818 (p < 0.0001), respectively]. A large difference between the DAS28 remission rate and CDAI remission rate was observed at week 24. However, these results are comparable to those of a previous study conducted with non-TCZ-treated patients. Moreover, the same results were obtained in the comparison between the DAS28-ESR and SDAI, even though the SDAI includes an inflammatory parameter as a component. These results confirm that the DAS28-ESR has a validity comparable to that of other methods in terms of evaluating the RA treatment efficacy of TCZ, despite its strong inflammatory marker-inhibiting effects.