Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.

Ankylosing Spondylitis Disease Activity Score (ASDAS): Defining Cut-Off Values for Disease Activity States and Improvement Scores.

Machado1,  Pedro, Landewe7,  Robert, Lie3,  Elisabeth, Kvien2,  Tore K., Braun6,  Juergen, Baker5,  Daniel G., Heijde4,  Desiree M. Van Der

Coimbra University Hospital, Coimbra, Portugal; Leiden University Medical Center, Leiden, The Netherlands
Diakonhjemmet Hospital, Oslo, Oslo, Norway
Diakonhjemmet Hospital, Oslo, Norway
Leiden University Medical Center, Meerssen, The Netherlands
Research and Development, Centocor Inc, Malvern, PA
Rheumazentrum Ruhrgebiet, Herne, Germany
Univ Hosp Maastricht, Maastricht, The Netherlands


ASDAS is a new composite index to assess disease activity in ankylosing spondylitis (AS). It has high construct and discriminatory validity. Criteria for disease activity states and improvement scores are important for clinical trials and clinical practice and have not been developed so far. Our aim was to determine clinically relevant cut-off values for disease activity states and improvement scores using the ASDAS.


The ASDAS is calculated using BASDAI questions 2, 3 and 6, patient global assessment (all 0–10cm VAS) and CRP (mg/L). We performed receiver operating characteristic (ROC)-curve analysis against several external criteria (ExCr) and used several approaches to determine the optimal cut-off (fixed 90% specificity, Youden index and closest point to (0,1)). The final choice was made on clinical and statistical grounds, after debate and voting by Assessment in SpondyloArthritis Society (ASAS) members. For the identification of proposed cut-offs we used baseline (BL) and 3-month (M) data of NOR-DMARD (N=295–477), a registry that includes AS patients starting a conventional DMARD or a TNF-blocker. Cross-validation was performed in ASSERT, a database of AS patients participating in a randomized placebo-controlled trial with infliximab.


Four disease activity states were chosen by consensus: inactive disease, moderate-, high- and very high disease activity. The 3 cut-offs for separating them were: 1.3 (ExCr: ASAS partial remission, patient and physician global <1cm), 2.1 (ExCr: patient and physician global <3cm) and 3.5 (ExCr: patient and physician global >6cm). Selected cut-offs for improvement scores were: change >=1.1 units for clinically important improvement (ExCr: patient reporting as being "better" or "much better" since start of treatment) and change >=2.0 units for major improvement (ExCr: patient reporting as being "much better" since start of treatment). Results of the cross-validation in ASSERT strongly supported the cut-offs (tables 1 and 2).

Table 1. Disease activity states (%) in ASSERT: Infliximab vs Placebo (Chi2, p-value)

Time-pointnASAS Partial RemissionASDAS <1.31.3 <= ASADAS < 2.12.1 <= ASDAS <= 3.5ASDAS >3.5
BL166 vs 570 vs 0 (NA)0 vs 0 (NA)1.2 vs 1.8 (0.1, 0.756)30.1 vs 26.3 (0.3, 0.586)68.7 vs 71.9 (0.2, 0.645)
3M163 vs 5621.5 vs 1.8 (11.8, 0.001)25.8 vs 1.8 (15.2, <0.001)26.4 vs 3.6 (13.3, <0.001)38.7 vs 39.3 (0.01, 0.933)9.2 vs 55.4 (53.5, <0.001)
6M163 vs 5623.3 vs 1.8 (13.2, <0.001)31.9 vs 0 (23.4, <0.001)23.3 vs 12.5 (3.0, 0.084)32.5 vs 33.9 (0.04, 0.846)12.3 vs 53.6 (40.6, <0.001)

Table 2. Improvement criteria (%) in ASSERT: Infliximab vs Placebo

Improvement criteria3 months (n=164 vs 56)chi-square (p-value)6 months (n=163 vs 56)chi2 (p-value)
D ASDAS>= 1.171.3 vs 19.645.9 (<0.001)69.3 vs 23.236.3 (<0.001)
D ASDAS>=2.043.9 vs 3.630.4 (<0.001)50.9 vs 5.436.3 (<0.001)
D BASDAI>=260.4 vs 23.223.1 (<0.001)62.6 vs 19.630.8 (<0.001)
BASDA15050.6 vs 10.727.6 (<0.001)51.5 vs 12.526.1 (<0.001)
ASAS2064.0 vs 25.025.6 (<0.001)63.2 vs 21.429.2 (<0.001)
ASAS4050.6 vs 16.120.5 (<0.001)47.2 vs 14.319.1 (<0.001)


Cut-off values for disease activity states and improvement scores using the ASDAS have been developed. They proved to have external validity and a very good performance compared to existing criteria.

To cite this abstract, please use the following information:
Machado, Pedro, Landewe, Robert, Lie, Elisabeth, Kvien, Tore K., Braun, Juergen, Baker, Daniel G., et al; Ankylosing Spondylitis Disease Activity Score (ASDAS): Defining Cut-Off Values for Disease Activity States and Improvement Scores. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :1922
DOI: 10.1002/art.29687

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