Abstract
IntroductionTo determine the validity and reliability of patients' self-performed joint counts compared to joint counts by professional assessors in rheumatoid arthritis (RA) patients in different disease activity states.MethodsIn patients with established RA we determined the inter-rater reliability of joint counts performed by an independent evaluator and the patient using intraclass correlation (ICC), and agreement on activity in individual joints by kappa statistics. We also performed longitudinal analyses to assess consistency of assessments over time. Finally, we investigated the concordance of joint counts of different assessors in patients with different levels of disease activity.ResultsThe reliability of patient self-performed joint counts was high when compared to independent objective assessment (ICC; 95%confidence interval (CI)) for the assessment of swelling (0.32; 0.15 to 0.46) and tenderness (0.75; 0.66 to 0.81), with higher agreement for larger joints (kappa: 0.57 and 0.45, respectively) compared to smaller joints (metacarpo-phalangeal joint (MCPs): 0.31 and 0.45; and proximal interphalangeal joint (PIPs): 0.22 and 0.47, for swelling and tenderness, respectively).Patients in remission according to the Simplified Disease Activity Index (SDAI ≤ 3.3) showed better concordance of the joint counts (swollen joint count (SJC) ties 25/37, tender joint count (TJC) ties 26/37) compared to moderate/high disease activity states (SDAI > 11; MDA/HDA: SJC ties 9/72, TJC ties 21/72). Positive and negative predictive values regarding the presence of SDAI remission were reasonably good (0.86 and 0.95, respectively). A separate training session for patients did not improve the reliability of joint assessment. The results were consistent in the longitudinal analyses.ConclusionsSelf-performed joint counts are particularly useful for monitoring in patients having attained remission, as these patients seem able to detect state of remission.
Highlights
To determine the validity and reliability of patients’ self-performed joint counts compared to joint counts by professional assessors in rheumatoid arthritis (RA) patients in different disease activity states
Cross sectional analysis of inter-rater variability Using intraclass correlation (ICC) we found significant consistency of patient derived joint counts with those of the two independent observers (P < 0.003) (Table 2) at both visits
To investigate whether discrepancies in joint assessment were consistent over time we used ICC, correlating differences between patient and observer derived joint counts at baseline with those at follow up; these analyses showed that the discrepancy was similar over time, that is, a good correlation of discrepancy at the two time points, ICC (95% confidence interval (CI)) swollen joint count (SJC) = 0.56 (0.44 to 0.66); tender joint count (TJC) = 0.36 (0.21 to 0.50) (P < 0.001)
Summary
To determine the validity and reliability of patients’ self-performed joint counts compared to joint counts by professional assessors in rheumatoid arthritis (RA) patients in different disease activity states. Rheumatoid arthritis is a chronic disease characterized by an inflammatory process which, over time, leads to irreversible joint destruction. This joint damage is unequivocally related to the clinical involvement of the joints [1,2]; assessment of joint involvement by examining their swelling and tenderness is crucial in RA. The state of remission is superior to other disease activity states, including low disease activity, with regard to structural, functional, and economic outcomes [5,6] This is reflected in the 2010 European League against Rheumatism (EULAR) management recommendations for RA, which suggest constant evaluations and rapid treatment adaptations until the goal of remission is reached [4]
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