New response thresholds for rheumatoid arthritis (RA), developed through a UK-led analysis, demonstrate improved correlation with ultrasound-detected synovitis and the potential to refine early treatment decision-making.

The study, published in the journal RMD Open, focused on the two-component Disease Activity Score in 28 joints (2C-DAS28), which includes swollen joint count (SJC28) and C-reactive protein (CRP), and excludes subjective components such as tender joint count and patient global assessment.

Three UK cohorts representing different stages of RA treatment were analysed: patients with early disease starting methotrexate (n=1,051); those with established RA receiving tumour necrosis factor inhibitors (n=989); and patients with late-stage disease undergoing subsequent therapies (n=301).

Across cohorts, patients were predominantly female, with disease duration increasing from a median of 0.7 years in early RA to 13 years in late-stage disease. Baseline disease activity was higher in more advanced cohorts, and notably, up to 63% of early RA patients had normal CRP levels at baseline, highlighting the heterogeneity of inflammatory burden.

New 2C-DAS28 thresholds and RA treatment response

An independent validation cohort from the Response, Relapse and Resistance to Rituximab in Rheumatoid Arthritis – or R4RA – study (n=161) was used to assess the primary outcome of inflammation response at three months.

Inflammation response was defined as achieving either remission (2C-DAS28 <1.8) or a clinically meaningful reduction in disease activity (Δ2C-DAS28 >1.7) and was correlated against ultrasound-detected synovitis, including synovial thickness and power Doppler (PD) scores, as an outcome measure.

Using these criteria, 55% of patients across the discovery cohorts were classified as responders at three months, compared with 30% achieving a comparable response using the Clinical Disease Activity Index.

Crucially, 2C-DAS28 response showed a significant correlation with ultrasound-detected synovitis in the validation cohort, including reductions in synovial thickness (r=−0.25; P=0.037) and PD scores (r=−0.28; P=0.042).

In contrast, conventional response criteria did not demonstrate a significant relationship with imaging markers of inflammation.

The study also demonstrated important prognostic value. Patients achieving a 2C-DAS28 response at three months were more than three times as likely to reach remission at six months (odds ratio 3.41, 95% CI 1.64–7.09).

These patients consistently showed lower disease activity across multiple clinical measures, reinforcing the importance of early inflammatory control in RA management.

The authors acknowledged several limitations, including the absence of ultrasound data in the discovery cohorts and the relatively modest size of the validation cohort. Early RA was also under-represented in imaging analyses, they said.

While statistically significant, correlations with synovitis were modest (r≈0.3), reflecting both disease complexity and limitations of current measurement tools.

Towards inflammation-driven treatment strategies

Overall, inflammation-focused scoring appears to more accurately reflect underlying disease biology than traditional composite measures, which can be influenced by pain, comorbidities and other non-inflammatory factors.

Criteria based on the 2C-DAS28 score enable the identification of patients who show significant improvement in clinical inflammation within three months of treatment, as well as those who do not.

Because these criteria correlate more strongly with active joint inflammation than traditional outcome measures, they may also support efforts to identify biomarkers of targeted treatment response, the authors concluded.

Early control of inflammation was also associated with better clinical outcomes, prompting the authors to suggest that the 2C-DAS28 scoring criteria could enhance existing measures to guide clinical management and help to identify those patients whose disease activity is driven by non-inflammatory features that may not respond to treatment escalation.

Reference
Stadler M et al. Inflammation response criteria for rheumatoid arthritis based on the two-component disease activity score. RMD Open 2026;12:e006631.