Background In recent years, disease remission in rheumatoid arthritis (RA) has been assessed using various disease activity indices such as the DAS28, SDAI, CDAI, ACR/EULAR-recommended Boolean definition and the Patient Activity Scale (PAS).
Objectives The aim of this analysis is to describe the agreement between these five indices in classifying remission as well as to assess their correlation in a routine clinical care setting.
Methods BioTRAC is an ongoing, prospective Canadian registry of rheumatology patients initiating treatment with infliximab or golimumab. In this analysis, data from RA patients who were treated with infliximab between January 2002 and June 2011 and had available information in all indices were used. The definitions for remission were as follows: DAS28-ESR < 2.6; SDAI ≤ 3.3, CDAI ≤ 2.8; PAS ≤ 1.0. Factor analysis was used to assess the variability due to each of the indices while inter-item correlation was measured with the Pearson correlation coefficient.
Results Seven hundred twenty five RA patients who had 2,897 complete assessments were included in the analysis. Non-remission was classified by all indices in 68.8% of the cases, while 31.2% achieved remission in one (12.4%), two (3.5%), three (3.4%), four (4.2%) and all five types (7.7%) of indices. Factor analysis showed that PAS accounted for 71.5% of the matrix variance, followed by DAS28-ESR (12.4%), SDAI (9.2%), CDAI (5.2%), and Boolean remission (1.6%), suggesting that PAS may reflect different aspects than the clinical indices. PAS remission revealed the lowest correlation with remission classified by the remaining indices (Table 1) and removal of any index, except PAS, would result in a lower overall Cronbach’s alpha.
Conclusions The results of this analysis show that variability exists in the classification of remission by various disease activity indices. This variability was found to be predominantly due to the Patient Activity Scale, a patient-driven composite tool, suggesting that the patient perception of disease activity may differ from that captured by clinical outcome measures.
Disclosure of Interest W. Bensen: None Declared, A. Jovaisas: None Declared, C. Thorne: None Declared, P. Baer: None Declared, M. Khraishi: None Declared, S. Dixit: None Declared, D. Choquette: None Declared, M. Starr: None Declared, I. Fortin: None Declared, D. Sholter: None Declared, E. Rampakakis Employee of: JSS Medical Research, J. Sampalis Employee of: JSS Medical Research, A. Lehman Employee of: Janssen, F. Nantel Employee of: Janssen, M. Shawi: None Declared, S. Otawa Employee of: Janssen