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Cut-Offs for Disease Activity States in Axial Spondyloarthritis With Ankylosing Spondylitis Disease Activity Score
Stylianos Georgiadis1, Lykke Midtbøll Ørnbjerg2, Brigitte Michelsen3
1S. Georgiadis, PhD, L.M. Ørnbjerg, MD, PhD, Copenhagen Center for Arthritis Research (COPECARE), Center for Rheumatology and Spine Diseases, Centre for Head and Orthopaedics, Rigshospitalet, Glostrup, Denmark; stylianos.georgiadis@regionh.dk.
Insights
This study estimated optimal Ankylosing Spondylitis Disease Activity Score based on erythrocyte sedimentation rate (ASDAS-ESR) cut-offs for axial spondyloarthritis (axSpA). The new cut-offs did not significantly improve agreement with ASDAS based on C-reactive protein (ASDAS-CRP) disease activity states.
Area of Science:
- Rheumatology
- Clinical Assessment
- Biomarkers
Background:
- The Ankylosing Spondylitis Disease Activity Score based on C-reactive protein (ASDAS-CRP) is preferred for assessing axial spondyloarthritis (axSpA) disease activity over ASDAS based on erythrocyte sedimentation rate (ASDAS-ESR).
- Current guidelines use identical disease activity cut-offs for both ASDAS-CRP and ASDAS-ESR, despite them not being interchangeable.
Purpose of the Study:
- To estimate optimal ASDAS-ESR values that correspond to established ASDAS-CRP cut-offs (1.3, 2.1, 3.5).
- To evaluate if applying these estimated ASDAS-ESR cut-offs improves the agreement between disease activity states assessed by ASDAS-ESR and ASDAS-CRP.
Main Methods:
- Utilized data from 3664 patients with axSpA across 9 European registries initiating TNF inhibitor therapy.
- Estimated ASDAS-ESR cut-offs using the Youden index method.
- Compared the level of agreement between disease activity states derived from ASDAS-ESR and ASDAS-CRP before and after applying the estimated cut-offs.
Main Results:
- Mean ASDAS-CRP was consistently higher than ASDAS-ESR at baseline and follow-up.
- Estimated optimal ASDAS-ESR cut-offs were determined to be 1.4, 1.9, and 3.3.
- Applying these estimated cut-offs reduced discordance in baseline data (22.93% to 19.81%) but increased it in follow-up data (27.17% to 28.94%).
Conclusions:
- Optimal ASDAS-ESR values corresponding to ASDAS-CRP cut-offs were estimated.
- The application of these estimated cut-offs did not substantially enhance the agreement between ASDAS-ESR and ASDAS-CRP disease activity states.
- The findings do not provide sufficient evidence to challenge the established ASDAS-ESR cut-off values.
Objective:
Ankylosing Spondylitis Disease Activity Score based on C-reactive protein (ASDAS-CRP) is recommended over ASDAS based on erythrocyte sedimentation rate (ASDAS-ESR) to assess disease activity in axial spondyloarthritis (axSpA). Although ASDAS-CRP and ASDAS-ESR are not interchangeable, the same disease activity cut-offs are used for both. We aimed to estimate optimal ASDAS-ESR values corresponding to the established ASDAS-CRP cut-offs (1.3, 2.1, and 3.5) and investigate the potential improvement of level of agreement between ASDAS-ESR and ASDAS-CRP disease activity states when applying these estimated cut-offs.
Methods:
We used data from patients with axSpA from 9 European registries initiating a tumor necrosis factor inhibitor. ASDAS-ESR cut-offs were estimated using the Youden index. The level of agreement between ASDAS-ESR and ASDAS-CRP disease activity states was compared against each other.
Results:
In 3664 patients, mean ASDAS-CRP was higher than ASDAS-ESR at both baseline (3.6 and 3.4, respectively) and aggregated follow-up at 6, 12, or 24 months (1.9 and 1.8, respectively). The estimated ASDAS-ESR values corresponding to the established ASDAS-CRP cut-offs were 1.4, 1.9, and 3.3. By applying these cut-offs, the proportion of discordance between disease activity states according to ASDAS-ESR and ASDAS-CRP decreased from 22.93% to 19.81% in baseline data but increased from 27.17% to 28.94% in follow-up data.
Conclusion:
We estimated the optimal ASDAS-ESR values corresponding to the established ASDAS-CRP cut-off values. However, applying the estimated cut-offs did not increase the level of agreement between ASDAS-ESR and ASDAS-CRP disease activity states to a relevant degree. Our findings did not provide evidence to reject the established cut-off values for ASDAS-ESR.
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