Background/Purpose: Interleukin-6 (IL-6) has been demonstrated to play a pathological role in rheumatoid arthritis (RA). IL-6 strongly induces production of C-reactive protein (CRP) and fibrinogen in hepatocytes. Marked decrease of serum CRP level and erythrocyte sedimentation rate (ESR) has been shown soon after administration of IL-6 antagonist, tocilizumab (TCZ). Therefore, usual disease activity scores using clinical data including CRP or ESR may not reflect real clinical response to the treatment with TCZ in patients with RA. RAPID3 includes the 3 patient-reported RA core data set measures: physical function, pain, and patient global estimate without formal joint counts and laboratory test, ESR or CRP. We investigated the usefulness of RAPID3 to evaluate disease activity and functional disability in RA patients receiving TCZ.

Methods: Twenty four patients with RA were enrolled in this prospective, IRB proven study. The patients were started on TCZ therapy at Saitama Medical University Hospital from 2010 to 2012. TCZ was infused every 4 weeks at a dose of 8 mg/kg. All patients were followed up to week 52. RAPID3 was calculated from a multidimensional health assessment questionnaire, pain and patient global estimate. The primary outcomes were the DAS28-ESR, CDAI, SDAI, HAQ and RAPID3 at week 52 of TCZ treatment. Secondary outcomes included proportion of patients in remission of RAPID3 or other indices to assess patients with RA. The association between RAPID 3 and other indices at week 52 was also examined.

Results: Mean age of patients was 53 years, 71 percent of patients were female, the mean duration of disease was 10 years and 75 percent of patients had received prior treatment of other biologics. Seventy one percent of patients were methotrexate users and 67 percent were corticosteroid users. Significant reduction of DAS28-ESR, CDAI, SDAI and RAPID3 were observed at week 52 compared to baseline (P<0.05). Remission rate of RAPID3 (29%) was not significantly different with that of CDAI (17%), SDAI (25%), ACR/EULAR Boolean (17%) and HAQ (38%) in patients receiving TCZ for 52 weeks, although the remission rate of RAPID3 was lower than that of DAS28-ESR (54%) (p=0.07). RAPID3 scores were correlated significantly with those of DAS28-ESR (rho = 0.66), CDAI (rho = 0.79), SDAI (rho = 0.78) and HAQ (rho = 0.85) (all P<0.001) at week 52.

Conclusion: RAPID3 may be useful for evaluating disease activity and functional disability without formal joint counts and laboratory tests in RA patients receiving TCZ.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/evaluation-of-disease-activity-by-the-routine-assessment-of-patient-index-data-3-in-patients-with-rheumatoid-arthritis-receiving-tocilizumab/