Variability in the Classification of Remission Among Disease Activity Indices and Their Correlation: An Analysis From a Prospective, Observational Registry

William G. Bensen¹, Algis V Jovaisas², J. Carter Thorne³, Philip Baer⁴, Majed M. Khraishi⁵, Sanjay Dixit⁶, Denis Choquette⁷, Michael Starr⁸, Isabelle Fortin⁹, Dalton E. Sholter¹⁰, Emmanouil Rampakakis^11,12, John S. Sampalis^11,12, Francois Nantel¹³, Allen J. Lehman¹⁴, May Shawi¹⁵ and Susan M. Otawa¹⁴, ¹Department of Medicine, Division of Rheumatology, Clinical Professor, McMaster University, Hamilton, ON, Canada, ²Division of Rheumatology, University of Ottawa, Ottawa, ON, Canada, ³Southlake Regional Health Centre, Newmarket, ON, Canada, ⁴Private Practice, Scarborough, ON, Canada, ⁵Nexus Clinical Research, St John's, NF, Canada, ⁶McMaster University, Hamilton, ON, Canada, ⁷Rheumatology, Institut de rhumatologie de Montréal (IRM), Montréal, QC, Canada, ⁸Montreal General Hospital, Montreal, QC, Canada, ⁹Centre de rhumatologie de l'est du Québec (CREQ), Rimouski, QC, Canada, ¹⁰Rheumatology Associates, Edmonton, AB, Canada, ¹¹JSS Medical Research, Montreal, QC, Canada, ¹²Jewish General Hospital, McGill University, Montreal, QC, Canada, ¹³Janssen Inc., Toronto, ON, Canada, ¹⁴Medical Affairs, Janssen Inc., Toronto, ON, Canada, ¹⁵Medical Affairs, Janssen Canada Inc, Toronto, ON, Canada

Meeting: 2013 ACR/ARHP Annual Meeting

Keywords: Disease Activity, outcome measures and remission

Session Information

Title: Rheumatoid Arthritis-Clinical Aspects III: Outcome Measures, Socioeconomy, Screening, Biomarkers in Rheumatoid Arthritis

Session Type: Abstract Submissions (ACR)

Background/Purpose: In recent years, disease remission in rheumatoid arthritis (RA) has been assessed using various disease activity indices such as the DAS28-CRP, SDAI, CDAI, ACR/EULAR-recommended Boolean definition and the Patient Activity Scale (PAS).

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 <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 thirty four RA patients who had 3,035 complete assessments were included in the analysis. Non-remission was classified by all indices in 63.1% of the cases, while 36.9% achieved remission in one (13.1%), two (7.8%), three (1.9%), four (4.9%) and all five types (9.1%) of indices. Factor analysis showed that PAS accounted for 70.4% of the matrix variance, followed by DAS28-CRP (13.4%), SDAI (9.0%), CDAI (5.6%), 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.

Conclusion: 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.

Table 1. Inter-Item Correlation Matrix of Disease Activity Indices
	PAS	DAS28-CRP	SDAI	CDAI	Boolean
PAS	N/A	0.466	0.520	0.521	0.381
DAS28-CRP	0.466	N/A	0.653	0.626	0.661
SDAI	0.520	0.653	N/A	0.918	0.739
CDAI	0.521	0.626	0.918	N/A	0.718
Boolean	0.381	0.661	0.739	0.718	N/A

Disclosure:

W. G. Bensen,
None;

A. V. Jovaisas,
None;

J. C. Thorne,
None;

P. Baer,
None;

M. M. Khraishi,

Hoffman-La Roche Canada, Amgen and Pfizer Canada, and Abbott Canada.,

S. Dixit,
None;

D. Choquette,
None;

M. Starr,
None;

I. Fortin,
None;

D. E. Sholter,
None;

E. Rampakakis,
None;

J. S. Sampalis,
None;

F. Nantel,
None;

A. J. Lehman,

Janssen Canada,

M. Shawi,

Janssen Canada,

S. M. Otawa,

Janssen Canada,

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