Look beyond the disease activity score of 28 joints (DAS28): tender points influence the DAS28 in patients with rheumatoid arthritis

Abstract

Objective: To explore the influence of tender points (TP) on the Disease Activity Score assessing 28 joints (DAS28) in patients with rheumatoid arthritis (RA).

Methods: In 200 consecutive patients with RA from the outpatient clinic, DAS28 and its components, tender and swollen joint counts (TJC, SJC, respectively), visual analog scale (VAS) for patient's general health (GH), and erythrocyte sedimentation rate (ESR), along with a tender point count (TPC) were assessed. Patients were categorized according to 4 TPC classes: zero, 1-5, 6-10, and ≥ 11 TP. The influence of TPC classes on DAS28 and its individual components was determined with Kruskal-Wallis tests and correlations between TP and DAS28 and its components were calculated.

Results: In 196 eligible patients, 70% were female, mean age was 59 years, and median disease duration was 3.9 years; median DAS28 was 3.1; and 49% had active disease, defined as DAS28 > 3.2. In 15% of patients, the TPC was ≥ 11, in 12% 6-10, in 30% 1-5, and in 43% zero. TPC significantly influenced the DAS28 and its less objective components TJC and VAS-GH (i.e., based on patient's report), but not the more objective DAS28 components SJC and ESR (i.e., observer- and laboratory-based).

Conclusion: DAS28 is influenced by tender points, even in the non-fibromyalgia range, falsely suggesting higher disease activity and decreasing the sensitivity of the DAS28 criterion of low disease activity or remission. When applying DAS28-guided "tight control" or "treat-to-target" treatment strategies in RA, evaluation of not only the DAS28, but also its individual components along with a full joint and physical evaluation including assessment of TP is required to reliably estimate the individual's disease activity, which guides therapeutic decisions.