Poor to modest agreement between rheumatoid arthritis response measures in clinical practice

CER3604
2009 Vol.27, N°4
PI 0633, PF 0640
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PMID: 19772796 [PubMed]

Abstract

OBJECTIVES:
To evaluate the agreement among several rheumatoid arthritis (RA) response measures in a clinical setting.
METHODS:
529 patients with RA were seen at 2 regular visits where the following response measures were determined: ACR-20, EULAR good or moderate (EULAR-GM), Simplified Disease Activity Index moderate (SDAI-M), Clinical DAI moderate (CDAI-M), and Patient Reported Outcomes Index-M 20 (PRO-IM-20). Each measure was modified to include a `worse` response, i.e. the inverse of the respective guidelines for a positive improvement response.Introduced for comparison was the Real-time Assessment of Disease Activity in Rheumatoid Arthritis (RADARA), a response measure that registers improvement if the patient`s tender and swollen joint counts and HAQ score all improve and worsening if all three increase. Contingency tables comparing the three responses (worse, no change, and improvement) along with Cohen`s kappa were calculated.
RESULTS:
The mean (SD) baseline characteristics of the patients included: age 66.5 (10.7) years, RA duration 12.9 (11.0) years, 91.3% male, 84.1% rheumatoid factor positive, and a Disease Activity Score-28 of 3.5 (1.3). The percentage of patients who improved/worsened were as follows: ACR-20 4.7/9.1, EULAR-GM 23.4/26.3, SDAI-M 16.1/20.6, CDAI-M 16.3/20.0, PRO-IM-20 22.5/34.4, and RADARA 7.0/11.5. Agreement (kappa) was poor to slight (≤ 0.4) between most of the response measures with the exception of RADARA/ACR-20 which showed substantial agreement (0.67) and SDAI/EULAR-GM and CDAI/EULAR-GM, which showed moderate agreement (0.54 and 0.52, respectively).
CONCLUSIONS:
RA response measures can be made more informative by the addition of a `worse` response, although even in this case the agreement in the clinic setting is primarily poor to moderate.