Background Treat-to-target strategies require instruments for valid detection of joint inflammation. In clinical practice, Disease Activity Score 28 (DAS28) is often used for this purpose. Patient-derived joint counts are a potential alternative for determining DAS28.
Objectives The aim of this study is to evaluate the reliability of patient derived joint counts and to test how often DAS28 based treatment decisions are different when patient-derived DAS28 (patDAS28) in stead of physician derived DAS28 (physDAS28) are used.
Methods This study was part of a study on assessment of synovitis in the hand and wrist in RA in which 59 patients with rheumatoid arthritis (RA) were included. Of these, 20 patients with DAS28 < 2.6, 26 with 2.6 < DAS28 >5.1 and 13 with DAS28> 5.1. Patients completed a self-assessment of joint tenderness and swelling of 44 joints. At the same day, counts of swollen (SJC) and tender joints (TJC) of 44 joints have been performed by two experienced examiners. Disease activity was classified as remission (DAS28 < 2.6), low-disease activity (2.6 < DAS28 >5.1) and high disease activity (DAS28> 5.1). Spearman’s rho correlation coefficients were used to test the relationship between the joint counts. The agreement in the classification of disease activity is given in percentages. Factors related to differences between physDAS28 and patDAS28 (sex, age and disease duration) were explored using logistic regression analyses.
Results Of the 59 included patients (61% women), the mean age was 55 (SD ± 13) years and on average they had been diagnosed with RA 7.5 years ago. There were high correlation coefficients for the relationship between patDAS28 and physDAS28 (examiner 1 r= 0.90, examiner 2 r=0.87 ). Age, sex and disease duration were not related to differences between physDAS28 and patDAS28. The correlations between TJC were higher (r= 0.72 and r= 0.65) than between SJC (r=0.47 and r= 0.45). The correlation between the two examiners was high for both tender (r=0,82) and swollen (r=0,85) joints. Using the DAS28 cut-off points, in 82% of the patients agreement with regard to the disease activity classification as compared to mean physDAS28. According to patDAS28 22% remission, 40% low-disease activity, and 20% high disease activityy and according to the average of examiners 32%, 40% and 20% respectively. Agreement of the disease activity classification between examiners was 92%.
Conclusions Patient-derived joint counts might be useful to evaluate disease activity in patients with RA.
Disclosure of Interest None Declared
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