Concordance and correlation of activity indices in patients with rheumatoid arthritis in northwestern Colombia: A cross-sectional study

Abstract

Aim: To determine the correlation and concordance between different clinimetric scores in patients with rheumatoid arthritis in two high-complexity reference centers in northwestern Colombia.

Method: A cross-sectional study in adults diagnosed with rheumatoid arthritis was conducted according to the 2010 American College of Rheumatology and European League Against Rheumatism Classification Criteria, between January and June, 2013. The correlation was evaluated using Spearman's correlation coefficient, and concordance with quadratic weighted kappa with the respective confidence intervals, for which patients were classified into different categories of disease activity.

Results: One hundred patients were included, of whom 83% were women; 58 and 75% received methotrexate and glucocorticoids, respectively. Most individuals were in remission or low activity. High correlations between Disease Activity Score of 28 joints - erythrocyte sedimentation rate (DAS28-ESR) values with DAS28 C-reactive protein and Simple Disease Activity Index (SDAI) with Clinical Disease Activity Index (P < 0.0001; r = 0.82 and r = 0.86, respectively) were observed; likewise, the scores obtained with different indices correlated well with gold standard values for remission (SDAI), where the correlation with DAS28-ESR was slightly lower. Excellent concordance among all clinimetric scores was observed, although it was lower among DAS28-ESR and SDAI.

Conclusion: Clinimetric indices had high concordance and correlation, especially for rheumatoid arthritis patients in remission or low disease activity, without being interchangeable among them.

Keywords: activity indices; concordance; correlation; rheumatoid arthritis.