Background/Purpose:

Patient-reported outcomes such as pain and patient global assessment of disease activity (PtGA) have been critiqued for not accurately assessing rheumatoid arthritis (RA) disease activity as they may reflect aspects not directly related to RA disease activity (e.g. fibromyalgia, low back pain, depression, etc.) or related to non-RA conditions. The aim of this analysis is to describe the relationship between patient-reported pain and disease activity levels, as measured with DAS28-ESR, CDAI, and SDAI, in a real-world, routine clinical care setting. An additional aim is to assess the occurrence of non-remission driven solely by pain using PtGA as a proxy for pain.

Methods:

Biologic Treatment Registry Across Canada (BioTRAC) is an ongoing, Canadian prospective 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 were used. Correlation of pain (VAS mm) with DAS28-ESR, CDAI and SDAI in a continuous or binary (low disease activity: yes vs. no; remission: yes vs. no) scale was assessed with linear regression and logistic regression, respectively. For the assessment of non-remission due to PtGA, DAS28-ESR, CDAI, and SDAI remission rates were compared to “non-PtGA” remission rates, calculated by subtracting the relative contribution of PtGA to the index.     

Results:

Eight hundred thirty eight RA patients who had 4,582 assessments were included in the analysis. A significant (P<0.001) positive linear relationship was found between pain and DAS28-ESR (standardized coefficient (β) = 0.662), CDAI (β = 0.660), and SDAI (β = 0.659). Increased pain was associated with reduced odds of achieving remission or low disease activity as defined by DAS28-ESR, CDAI, and SDAI (Table 1). Correlation analysis showed that a strong positive linear correlation existed between pain and PtGA (r = 0.914), supporting the use of PtGA as a proxy for pain. Cross-tabulation of remission achievement with “non-PtGA” remission achievement revealed that omission of PtGA from the DAS28-ESR, CDAI, and SDAI indices would result in the re-classification of an additional 2.0%, 9.3%, and 9.6% of the cases as remission.

 

Table 1. Relationship Between Pain (VAS mm) and Low Disease Activity or Remission
Disease Activity Threshold		OR	95% CI	P-Value
Low Disease Activity	DAS28-ESR	0.950	0.946, 0.954	<0.001
	CDAI	0.943	0.940, 0.947	<0.001
	SDAI	0.940	0.936, 0.944	<0.001
Remission	DAS28-ESR	0.946	0.941, 0.951	<0.001
	CDAI	0.890	0.880, 0.901	<0.001
	SDAI	0.892	0.881, 0.904	<0.001

 Conclusion:

The results of this analysis show that increased pain is associated with higher disease activity as measured by the DAS28-ESR, CDAI and SDAI, which may be due to the strong correlation of pain with PtGA. Omission of PtGA from these disease activity indices resulted in the classification of additional cases as remission cases to an extent that paralleled the strictness of the remission criteria (i.e., from the less “strict” DAS28-ESR index to the more “strict” SDAI). Therefore, the CDAI and SDAI might be more sensitive to pain not directly related to RA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/what-is-the-real-world-relationship-between-patient-reported-pain-or-patient-global-assessment-and-disease-activity-indices-in-rheumatoid-arthritis-an-analysis-from-the-prospective-observational-bi/