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Differential influence of Clinical Disease Activity Index components based on disease state in rheumatoid arthritis patients: real-world results from the Ontario Best Practices Research Initiative

1, 2, 3, 4, 5, 6


  1. Department of Rheumatology, University of Toronto, ON, Canada.
  2. Toronto General Hospital Research Institute, University Health Network, Toronto, and Institute of Health Policy, Management and Evaluation, University of Toronto, ON, Canada.
  3. Toronto General Hospital Research Institute, University Health Network, Toronto, ON, Canada.
  4. Toronto General Hospital Research Institute, University Health Network, Toronto; Department of Medicine (DMO) University of Toronto and Institute of Health Policy, Management, and Evaluation (IHPME), Toronto, and Mount Sinai Hospital, Division of Rheumatology, Toronto, ON, Canada.
  5. JSS Medical Research, St-Laurent, and Faculty of Medicine, McGill University, Montreal, QC, Canada.
  6. JSS Medical Research, St-Laurent, QC, Canada.

2022 Vol.40, N°11
PI 2147, PF 2152
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PMID: 35383561 [PubMed]

Received: 26/07/2021
Accepted : 10/01/2022
In Press: 30/03/2022
Published: 05/11/2022


The Clinical Disease Activity Index (CDAI) is routinely used in clinical care when treating-to-target RA patients. Previous validation studies have looked at CDAI’s overall performance; this analysis aimed at evaluating its properties by disease state and identifying drivers of variance.
RA patients enrolled in the OBRI registry, with available follow-up of ≥6 months were included. Construct validity of CDAI was assessed with principal component analysis; internal consistency with Cronbach’s alpha (α); correlational validity with Spearman’s rho (ρ); agreement in disease state classification with the kappa statistic. Stratification by disease states was performed.
CDAI correlation with DAS28 was strong when CDAI>10 (ρ=0.79), moderate when CDAI≤10 (ρ=0.56) or 2.810, CDAI was able to be reduced to a single component with patient global assessment (PtGA) having the lowest loading. When CDAI≤10, two distinct components were identified: (1) PtGA and physician global assessment; (2) SJC28 and TJC28. Moderate levels (α=0.71) of internal consistency were observed when CDAI>10 but low when CDAI≤10 (α=0.23), 2.8CONCLUSIONS:
CDAI and DAS28 correlated well in moderate/high disease activity and poorly in LDA/remission. PtGA correlated weakly with other CDAI components and had a stronger influence on CDAI in LDA/remission. Thus, careful interpretation of PtGA is necessary when making treatment decisions, particularly in patients in CDAI LDA who are non-remitters.


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