Disease activity score 28 may overestimate the remission induction of rheumatoid arthritis patients treated with tocilizumab: comparison with the remission by the clinical disease activity index

We evaluated the efficacy of tocilizumab (TCZ) in patients with rheumatoid arthritis (RA) by the clinical disease activity index (CDAI) and disease activity score (DAS) 28-erythrocyte sedimentation rate (ESR). Thirty-two RA patients received 8 mg/kg of TCZ intravenously every 4 weeks for 48 weeks. The therapeutic response was also evaluated in 30 RA patients treated with 3 mg/kg of infliximab (IFX) for 46 weeks. We compared the therapeutic course of TCZ with IFX in order to evaluate the efficacy of TCZ therapy. A strong positive correlation between CDAI and DAS28-ESR was observed at baseline, whereas their associations dropped significantly within the first 2 months. The association recovered to the baseline by IFX, but still remained low in TCZ. Although a decrement of DAS28-ESR was prominent in TCZ as compared with IFX, that of CDAI was significant in the early phase and even in the latter in patients treated by IFX. The present study revealed that DAS28-ESR may not be sufficient to estimate RA disease activity treated by TCZ, probably due to the significant effect toward inhibition of acute phase reactants by TCZ. CDAI is suggested to be an important alternate of composite measure in these cases.