Table Omitted - see PDF ] Table 1 Characteristics of patients who were either administered tocilizumab at different intervals or methotrexate 3-Week group (n?=?10) 4-Week group (n?=?10) 5-Week group (n?=?10) Control group (n?=?10) P value Sex (female, n/total n, %) 9/10, 90% 9/10, 90% 8/10, 80% 8/10, 80% 0.85 Age (years) 55.3 (14.8) 65.0 (9.9) 62.0 (10.6) 66.7 (11.0) 0.27 RA duration (months) 101.5 (86.5) 68.5 (74.6) 116.5 (92.5) 81.9 (78.7) 0.35 Tocilizumab duration (months) 27.1 (20.7) 11.9 (9.2) 39.6 (12.1) - <0.01* RF positive (n, %) 7/10, 70% 9/10, 90% 9/10, 90% 5/10, 50% 0.12 ACPA positive (n, %) 5/8, 63% 7/10, 70% 8/10, 80% 6/10, 60% 0.77 MTX use (n, %) 4/10, 40% 6/10, 60% 4/10, 40% 10/10, 100% 0.03* MTX dose (mg/week) 7.5 (4.1) 8.3 (2.0) 4.4 (0.9) 9.0 (3.6) 0.07 CRP (mg/dl) 0.01 (0.02) 0.01 (0.02) 0.03 (0.03) 0.13 (0.10) <0.01* ESR (mm/h) 6.0 (4.7) 6.6 (5.6) 12.3 (14.4) 22.2 (12.8) <0.01* CDAI 5.2 (1.3-8.1) 1.7 (0.1-7.9) 1.7 (0.1-5.8) 3.6 (0.2-6.3) 0.07 HAQ-DI 1.1 (0.8) 0.5 (0.6) 0.3 (0.5) 0.5 (0.5) 0.06 Values are expressed as mean?±?standard deviation (SD) unless stated otherwise RA rheumatoid arthritis, RF rheumatoid factor, ACPA anti-cyclic citrullinated peptide antibody, MTX methotrexate, CRP C-reactive protein, ESR erythrocyte sedimentation rate, CDAI clinical disease activity index, HAQ-DI health assessment questionnaire disability index *P?<?0.05 Proportion of pSTAT3-positive CD4+ T cells A representative figure showing the detection of pSTAT3-positive cells in whole blood from patients in each group is shown in Fig. 1a. Since CD4+ T cells were the most sensitive to IL-6 stimulation compared with CD3?+?CD4? T cells and CD3? cells (Fig. 1a), we focused on the proportion of pSTAT3-positive CD4+ T cells in the assay. [...]it is suggested that different TCZ treatment intervals were necessary to lower disease activity in each group of patients. Since the novel assay system utilized in this study uses whole blood that contains TCZ, detection of the proportion of pSTAT3-positive CD4+ T cells reflects the strength of IL-6 signal inhibition by TCZ in vivo, and it is a unique system for assessing patients with RA under TCZ treatment. Since the variation of %pSTAT3/CD4+ T cells within each group of TCZ-treated patients was relatively large, the pharmacokinetics/pharmacodynamics of TCZ might differ among individuals. [...]measurement of the proportion of pSTAT3-positive CD4+ T cells under IL-6 stimulation might support strategies to optimize treatment in patients with RA treated with TCZ.