Test–retest reliability of disease activity core set measures and indices in rheumatoid arthritis

Aim: To examine the test–retest reliability of the rheumatoid arthritis (RA) core disease activity measures and derived composite indices. Methods: A total of 28 stable patients with RA had 2 complete assessments within 1 week, which included the 7 RA core disease activity measures and derived disease activity indices (28-joint Disease Activity Score (DAS28), Simplified Disease Activity Index (SDAI), Clinical Disease Activity Index (CDAI), RA Disease Activity Index (RADAI) and Routine Assessment of Patient Index Data (RAPID3)). The intraclass correlations (ICC), the smallest detectable difference (SDD) and minimal detectable change as percentage of the maximum score (MDC%) were estimated as measures of test–retest reliability. Results: Correlations for the disease activity indices were high. SDDs (MDC%) to detect a true improvement or deterioration with 95% confidence were: DAS28 1.32 (14.4%), SDAI 8.26 (9.6%), CDAI 8.05 (10.6%), RAPID3 1.48 (14.8%) and RADAI 1.49 (14.9%). Thus, SDDs were rather high, and the MDC% values were of a similar magnitude of 10% to 15% for all seven core data set measures. Conclusions: SDDs of the DAS28, SDAI and CDAI were close to limits to detect important improvement. Clinicians should be aware of measurement error. Nonetheless, RA core data set measures and indices obtained from a health professional, laboratory and patient self-report had similar reliability.

[1]  J. Jacobs,et al.  Tight control in the treatment of rheumatoid arthritis: efficacy and feasibility , 2007, Annals of the rheumatic diseases.

[2]  P. Tugwell,et al.  A simplified disease activity index for rheumatoid arthritis for use in clinical practice. , 2003, Rheumatology.

[3]  M. Boers,et al.  Reliability of measures of disease activity and disease damage in rheumatoid arthritis: implications for smallest detectable difference, minimal clinically important difference, and analysis of treatment effects in randomized controlled trials. , 2001, The Journal of rheumatology.

[4]  P. van Riel,et al.  Validation of rheumatoid arthritis improvement criteria that include simplified joint counts. , 1998, Arthritis and rheumatism.

[5]  T. Kvien,et al.  Repeated measures in rheumatoid arthritis reduced the required sample size in a two-armed clinical trial. , 2008, Journal of clinical epidemiology.

[6]  B. Bresnihan,et al.  Consistency in assessing the Disease Activity Score-28 in routine clinical practice , 2007, Annals of the rheumatic diseases.

[7]  M. Prevoo,et al.  Modified disease activity scores that include twenty-eight-joint counts. Development and validation in a prospective longitudinal study of patients with rheumatoid arthritis. , 1995, Arthritis and rheumatism.

[8]  T. Pincus,et al.  An index of only patient-reported outcome measures, routine assessment of patient index data 3 (RAPID3), in two abatacept clinical trials: similar results to disease activity score (DAS28) and other RAPID indices that include physician-reported measures. , 2007, Rheumatology.

[9]  J. Smolen,et al.  The Simplified Disease Activity Index (SDAI) and Clinical Disease Activity Index (CDAI) to monitor patients in standard clinical care. , 2007, Best practice & research. Clinical rheumatology.

[10]  D. Altman,et al.  STATISTICAL METHODS FOR ASSESSING AGREEMENT BETWEEN TWO METHODS OF CLINICAL MEASUREMENT , 1986, The Lancet.

[11]  M. Liang,et al.  A self-administered rheumatoid arthritis disease activity index (RADAI) for epidemiologic research. Psychometric properties and correlation with parameters of disease activity. , 1995, Arthritis and rheumatism.

[12]  J J Anderson,et al.  The American college of rheumatology preliminary core set of disease activity measures for rheumatoid arthritis clinical trials , 1993 .

[13]  T. Kvien,et al.  Performance of health status measures with a pen based personal digital assistant , 2005, Annals of the rheumatic diseases.

[14]  M. Ensor,et al.  Does the Stanford Health Assessment Questionnaire have potential as a monitoring tool for subjects with rheumatoid arthritis? , 2001, Annals of the rheumatic diseases.

[15]  J. Ware,et al.  Determining minimally important changes in generic and disease-specific health-related quality of life questionnaires in clinical trials of rheumatoid arthritis. , 2000, Arthritis and rheumatism.