Is a Single Variable, The Swollen Joint Count, Valid As An Outcome Measure Separate From Being In An Index Measure? An Analysis From The Prospective, Biologic Treatment Registry Across Canada

J. Carter Thorne¹, Boulos Haraoui^2,3, William G. Bensen⁴, Algis Jovaisas⁵, Jude F. Rodrigues⁶, Denis Choquette², Alice V. Klinkhoff⁷, Emmanouil Rampakakis^8,9, John S. Sampalis^8,9, Francois Nantel¹⁰, Allen J. Lehman¹¹, May Shawi¹² and Susan M. Otawa¹¹, ¹Southlake Regional Health Centre, Newmarket, ON, Canada, ²Rheumatology, Institut de rhumatologie de Montréal (IRM), Montréal, QC, Canada, ³Department of Medicine, Centre Hospitalier de l’Université de Montréal, Montréal, QC, Canada, ⁴Department of Medicine, Division of Rheumatology, Clinical Professor, McMaster University, Hamilton, ON, Canada, ⁵Division of Rheumatology, University of Ottawa, Ottawa, ON, Canada, ⁶Rheumatology, Windsor, ON, Canada, ⁷The Mary Pack Arthritis Ctr, Vancouver, BC, Canada, ⁸JSS Medical Research, Montreal, QC, Canada, ⁹Jewish General Hospital, McGill University, Montreal, QC, Canada, ¹⁰Janssen Inc., Toronto, ON, Canada, ¹¹Medical Affairs, Janssen Inc., Toronto, ON, Canada, ¹²Medical Affairs, Janssen Canada Inc, Toronto, ON, Canada

Meeting: 2013 ACR/ARHP Annual Meeting

Keywords: outcome measures and rheumatoid arthritis (RA)

Session Information

Title: Rheumatoid Arthritis Treatment - Small Molecules, Biologics and Gene Therapy III

Session Type: Abstract Submissions (ACR)

Background/Purpose: The importance of joint counts as measures of synovitis is reflected in their prominence in all major clinical composite indices, the Disease Activity Score (DAS), the Clinical Disease Activity Index (CDAI) and the Simplified Disease Activity Index (SDAI). The twenty eight swollen joint count (SJC28) contributes numerically to approximately 16% of DAS28, 37% of CDAI and 33% of SDAI. The aim of this analysis was to examine whether SJC28 could be used as a stand-alone measure of disease remission.

Methods: Biologic Treatment Registry Across Canada (BioTRAC) is an ongoing, prospective registry of patients initiating treatment for RA, AS, or PsA with infliximab or golimumab as first biologics or after having been treated with a biologic for less than six months. In this analysis, data from RA patients treated with infliximab who were enrolled between January 2002 and June 2011 were used. Agreement between SJC28≤1 and remission or low disease activity as defined by the DAS28, CDAI, and SDAI criteria was assessed with the sensitivity, specificity, as well as the positive (PPV) and negative (NPV) predictive value.

Results: A total of 838 RA patients with mean (SD) age of 55.6 (13.5) years and mean (SD) duration since diagnosis of 10.5 (19.8) years were included in this analysis, providing information from 4,582 assessments. Using DAS28, CDAI, SDAI, and Boolean remission as reference standards, SJC28 sensitivity was 91.0%, 99.1%, 98.3%, and 100.0%, respectively. In addition, SJC28 correctly classified non-remission (NPV of 94.9%, 99.8%, 99.5%, and 100.0% for DAS28, CDAI, SDAI, and Boolean definition, respectively). However, specificity was only moderate (DAS28: 72.6%, CDAI: 64.0%, SDAI: 63.0%, Boolean: 61.8%), and SJC28 yielded a considerable proportion of false positives as indicated by the low PPV observed (DAS28: 58.9%, CDAI: 32.1%, SDAI: 33.0%, Boolean: 29.3%). When looking at low disease activity, SJC28≤1 showed lower sensitivity (DAS28: 83.2%, CDAI: 83.8%, SDAI: 85.0%) and NPV (DAS28: 85.8%, CDAI: 86.9%, SDAI: 87.5%) but higher specificity (DAS28: 83.2%, CDAI: 85.2%, SDAI: 84.2%) and PPV (DAS28: 80.1%, CDAI: 82.2%, SDAI: 81.1%).

Conclusion: The results of this analysis have shown that SJC28≤1 has high discriminatory power for low disease activity and moderate discriminatory power for remission as defined by the DAS28, CDAI and SDAI criteria. The more rigorous ACR/EULAR Boolean remission criteria were associated with increased sensitivity and NPV but decreased specificity and PPV.

Disclosure:

J. C. Thorne,
None;

B. Haraoui,
None;

W. G. Bensen,
None;

A. Jovaisas,

Janssen Pharmaceutica Product, L.P ,

J. F. Rodrigues,
None;

D. Choquette,
None;

A. V. Klinkhoff,
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,

« Back to 2013 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/is-a-single-variable-the-swollen-joint-count-valid-as-an-outcome-measure-separate-from-being-in-an-index-measure-an-analysis-from-the-prospective-biologic-treatment-registry-across-canada/