Test-retest reliability of the Disease Activity Score 28 CRP (DAS28-CRP), the Simplified Disease Activity Index (SDAI) and the Clinical Disease Activity Index (CDAI) in rheumatoid arthritis when based on patient self-assessment of tender and swollen joints

摘要

Composite disease activity scores are frequently used in daily practice as tools for treatment decisions in patients with rheumatoid arthritis (RA). If reliable, patient-reported disease activity may be time saving in the busy clinic. The objective was to examine the test-retest reliability of the Disease Activity Score 28 CRP (DAS28-CRP) with four variables (4v) and three variables (3v), the Simplified Disease Activity Index (SDAI) and the Clinical Disease Activity Index (CDAI) when based on patient self-assessment of tender and swollen joints and to examine the agreement between these scores and physician-derived scores. Thirty out-clinic RA patients with stable disease were included. A joint count was performed two times 1 week apart by the patient and by an experienced physician. Test-retest reliability was expressed as the least significant difference (LSD), as the LSD in percent of the mean score (%LSD) and as intra-individual coefficients of variation (CVi). Mean scores based on physician vs. patient joint counts (visit 1) were: DAS28-CRP(4v) 3.5 ± 1.0 vs. 3.6 ± 1.1 (not significant (NS)), DAS28-CRP(3v) 3.4 ± 0.9 vs. 3.5 ± 0.9 (NS), SDAI 14.2 ± 9.4 vs.14.1 ± 9.4 (NS) and CDAI 13.4 ± 9.3 vs. 13.3 ± 9.4 (NS). The LSDs (%LSD) for duplicate assessments of patient-derived scores (visit 2 vs. 1) were: DAS28-CRP(4v) 0.8 (23.2), DAS28-CRP(3v) 0.9 (25.2), SDAI 8.3 (59.9) and CDAI 8.4 (63.8). Similar LSDs were found for differences between duplicate assessments of physician-derived scores and for differences between physician and patient-derived scores. CVis for SDAI and CDAI were significantly higher than for DAS28-CRP(4v) and DAS28-CRP(3v) (p 0.005). Patient- and physician-derived scores agreed closely on group level. On the individual level, the LSDs between patient- and physician-derived scores were considerable but corresponded to both patient and physician intra-observer LSDs. Thus, scores based on patient-performed joint counts may be an alternative to traditional physician-derived scores in patients with stable disease.