Arthritis & Rheumatism, Volume 63,
November 2011 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Chicago, Illinois November 4-9, 2011.


Definition of Treatment Response in Rheumatoid Arthritis Based on the Simplified and the Clinical Disease Activity Index.

Aletaha1,  Daniel, Martinez-Avila2,  José, Kvien3,  Tore K., Smolen4,  Josef S.

Medical University of Vienna, Vienna, Austria
Medical University of Vienna, Austria
Diakonhjemmet Hospital, Oslo, Norway
Krankenhaus Lainz, Vienna, Austria

Background/Purpose:

The Simplified and the clinical disease activity indices (SDAI, CDAI) have been introduced to assess disease activity in a simple way and have shown their merits in clinical practice. In clinical trials of rheumatoid arthritis (RA), however, treatment efficacy has traditionally been assessed through response rates. Currently, no validated response definitions for the SDAI and CDAI are available.

We aimed to define minor, moderate, and major response criteria for the SDAI based on the agreement with the traditional way of response assessment by the American College of Rheumatology (ACR) 20%, 50%, and 70% improvement definition.

Methods:

We used data from two clinical trials on infliximab plus methotrexate (MTX) vs placebo plus MTX in early (ASPIRE) or established (ATTRACT) RA, and identified the three SDAI cutpoints based on the best agreement (by Kappa statistics) with the ACR20/50/70 responses. These cutpoints were then tested for face validity, construct, and discriminant validity in the trial datasets, and for construct validity and validity in regards to patients' reported perception of improvement in an observational dataset (NOR-DMARD).

Results:

Based on agreement with the ACR response, the minor, moderate, and major responses were identified as SDAI 50%, 70%, and 85% improvement. These cutpoints had good face validity, with major response bringing the majority of patients into remission or near remission, moderate response bringing the majority into at least low disease activity, and minor response essentially warranting that no patient remains in a high disease activity state. Construct validity was shown by a clear association of increasing SDAI response categories with increasing levels of functional improvement, and better functional states reached (see Figure). Also, the annual radiographic progression was greatest in SDAI non responders and increased across thes SDAI 50/70/85 response groups (mean: 5.9 vs. 3.9/2.2/-0.3). Across SDAI50/70/85 the sensitivities regarding patients' perceived improvement in NOR-DMARD decreased (73%/39%/22%) and the specificities increased (61%/89%/96%). Further, the identified cutpoints discriminated well between treatment arms in ASPIRE and ATTRACT. Results for the CDAI were not different to the SDAI, and thus the same cutpoints for definition of response were used.

Conclusion:

New cutpoints for response have been defined for the SDAI and the CDAI, and have been assessed for their validity. These criteria expand the usefulness of the SDAI and CDAI for their application as endpoints in clinical trials beyond the definition of disease activity categories.

To cite this abstract, please use the following information:
Aletaha, Daniel, Martinez-Avila, José, Kvien, Tore K., Smolen, Josef S.; Definition of Treatment Response in Rheumatoid Arthritis Based on the Simplified and the Clinical Disease Activity Index. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :2226
DOI:

Abstract Supplement

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