An external validation study reporting poor correlation between the claims-based index for rheumatoid arthritis severity and the disease activity score.

Abstract

INTRODUCTION:

We conducted an external validation study to examine the correlation of a previously published claims-based index for rheumatoid arthritis severity (CIRAS) with disease activity score in 28 joints calculated by using C-reactive protein (DAS28-CRP) and the multi-dimensional health assessment questionnaire (MD-HAQ) physical function score.

METHODS:

Patients enrolled in the Brigham and Women's Hospital Rheumatoid Arthritis Sequential Study (BRASS) and Medicare were identified and their data from these two sources were linked. For each patient, DAS28-CRP measurement and MD-HAQ physical function scores were extracted from BRASS, and CIRAS was calculated from Medicare claims for the period of 365 days prior to the DAS28-CRP measurement. Pearson correlation coefficient between CIRAS and DAS28-CRP as well as MD-HAQ physical function scores were calculated. Furthermore, we considered several additional pharmacy and medical claims-derived variables as predictors for DAS28-CRP in a multivariable linear regression model in order to assess improvement in the performance of the original CIRAS algorithm.

RESULTS:

In total, 315 patients with enrollment in both BRASS and Medicare were included in this study. The majority (81%) of the cohort was female, and the mean age was 70 years. The correlation between CIRAS and DAS28-CRP was low (Pearson correlation coefficient = 0.07, P = 0.24). The correlation between the calculated CIRAS and MD-HAQ physical function scores was also found to be low (Pearson correlation coefficient = 0.08, P = 0.17). The linear regression model containing additional claims-derived variables yielded model R(2) of 0.23, suggesting limited ability of this model to explain variation in DAS28-CRP.

CONCLUSIONS:

In a cohort of Medicare-enrolled patients with established RA, CIRAS showed low correlation with DAS28-CRP as well as MD-HAQ physical function scores. Claims-based algorithms for disease activity should be rigorously tested in distinct populations in order to establish their generalizability before widespread adoption.

• Authors: Rishi J Desai, Daniel H Solomon, Michael E Weinblatt, Nancy Shadick, Seoyoung C Kim
• Journal: Arthritis research & therapy (Arthritis Res Ther) Vol. 17 Pg. 83 (Apr 13 2015) ISSN: 1478-6362 [Electronic] England
• PMID: 25880932 (Publication Type: Journal Article, Observational Study, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Validation Study)

Topics

• Aged
• Aged, 80 and over
• Arthritis, Rheumatoid (diagnosis, epidemiology)
• Cohort Studies
• Female
• Humans
• Male
• Medicare (standards)
• Prospective Studies
• Registries (standards)
• Severity of Illness Index
• United States (epidemiology)