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The Ankylosing Spondylitis Disease Activity Score (ASDAS) is a measure of axial spondyloarthritis (axSpA) disease activity with validated cut-offs endorsed by the Assessment of SpondyloArthritis international Society (ASAS) and Outcome Measures in Rheumatology (OMERACT).1 2 In the 2016 update of the ASAS-European League Against Rheumatism (EULAR) management recommendations for axSpA, it is recommended that biological disease-modifying antirheumatic drugs should be considered in patients with persistently high disease activity despite conventional treatments, and that the preferred measure to define active disease should be the ASDAS (ASDAS of at least 2.1, ie, high disease activity).3 The 2017 update of treat-to-target recommendations in axial and peripheral SpA recommends that the treatment target should be inactive disease/clinical remission and that low/minimal disease activity may be an alternative treatment target. The same recommendations state that the preferred measure to define the target in axSpA is the ASDAS.4
ASDAS cut-offs for disease activity states are 1.3, separating ‘inactive disease’ from ‘moderate disease activity’, 2.1, separating ‘moderate disease activity’ from ‘high disease activity’, and 3.5, separating ‘high disease activity’ from ‘very high disease activity’. While inactive disease equates to a remission-like state, there is no low/minimal disease equivalent in the above nomenclature of ASDAS cut-offs. At the 2018 ASAS annual meeting in Lisbon, Portugal, ASAS members discussed the proposal of changing the nomenclature of ASDAS cut-offs in order to fill this gap.
Arguments to change the designation of ‘moderate disease activity’ to ‘low disease activity’ were presented. The compelling argument is the fact that the majority of patients in this ASDAS category have indeed mild disease activity, an observation that is in line with the external constructs that were used to derive the ASDAS cut-off of 2.1: patient and physician global assessments <3 using the 90% specificity criterion to determine the optimal cut-off.1 5 Furthermore, recent publications have shown that the majority of patients with ASDAS values in the ‘moderate disease activity’ category consider themselves as being in a patient-acceptable symptom state (PASS), which can be defined as the maximum level of symptoms with which patients consider themselves to be well. Godfrin-Valnet et al 6 found that the agreement between ASDAS-C-reactive protein (CRP) and ASDAS-erythrocyte sedimentation rate (ESR) was good and that values of ≤2.3 for each were associated with the PASS. A previous study by Rodríguez-Lozano et al 7 suggested cut-off values between 2.5 and 3.0 for ASDAS-CRP and cut-off values between 2.8 and 3.5 for ASDAS-ESR (PASS as external construct), depending on the method used to determine the cut-off value. A more recent study by Sellas et al 8 suggested that the ASDAS cut-off of 2.04 was associated with patient-PASS while the ASDAS cut-off of 2.44 was associated with physician-PASS.
Following an open discussion among ASAS members about the topic, the proposed nomenclature change from ASDAS ‘moderate disease activity’ to ASDAS ‘low disease activity’ was voted and approved by ASAS members (figure 1). Other possibilities that were considered but rejected by ASAS members were the use of the wording ‘low/moderate disease activity’, ‘mild disease activity’ and ‘moderate/high disease activity’ (the latter proposed to replace ‘high disease activity’ state).
In conclusion, the nomenclature of ASDAS disease activity states was updated by ASAS. The ‘moderate disease activity’ state is replaced by ‘low disease activity’ state, better reflecting the opinion of patients and physicians about what ASDAS values ≥1.3 and <2.1 represent. This change will improve the interpretability of ASDAS scores and will facilitate the implementation of treat-to-target strategies in axSpA.
Contributors PMM drafted the manuscript and is the first author of the ASDAS cut-offs manuscript published in 2011. DvdH led the discussion at the ASAS 2018 annual meeting and is the senior author of the ASDAS cut-offs manuscript published in 2011. RL was the president of ASAS at the ASAS 2018 annual meeting and a coauthor of the ASDAS cut-offs manuscript published in 2011. All authors read, commented on, and approved the final manuscript.
Funding PMM is supported by the National Institute for Health Research (NIHR) University College London Hospitals (UCLH) Biomedical Research Centre (BRC).
Disclaimer The views expressed are those of the authors and not necessarily those of the (UK) National Health Service (NHS), the NIHR or the (UK) Department of Health.
Competing interests PMM has received consulting/speaker’s fees from AbbVie, Centocor, Janssen, MSD, Novartis, Pfizer and UCB Pharma. RL has received consulting fees and/or research grants and/or speaker’s bureau from Abbott, Ablynx, Amgen, AstraZeneca, Bristol-Myers Squibb, Centocor, Glaxo-Smith-Kline, Merck, Novartis, Pfizer, Roche, Schering-Plough, UCB Pharma and Wyeth. DvdH has received consulting fees from AbbVie, Amgen, Astellas, AstraZeneca, Bristol-Myers Squibb, Boehringer Ingelheim, Celgene, Daiichi, Eli-Lilly, Galapagos, Gilead, Janssen, Merck, Novartis, Pfizer, Regeneron, Roche, Sanofi and UCB Pharma and is the director of Imaging Rheumatology BV.
Provenance and peer review Not commissioned; internally peer reviewed.