The Ankylosing Spondylitis Disease Activity Score now has established, clinically relevant cutoff values for disease activity states and improvement scores.
The validated criteria will be useful in clinical practice, epidemiologic studies, and clinical trials, according to Dr. Pedro Machado, a rheumatologist who is now a doctoral student at Leiden (the Netherlands) University Medical Center and Coimbra (Portugal) University Hospital, and who presented the validation findings.
The development and characteristics of the Ankylosing Spondylitis Disease Activity Score (ASDAS) have recently been described (Ann. Rheum. Dis. 2009;68:18–24;1811–8). The score is based on questions about back pain, duration of morning stiffness, and peripheral pain/swelling and scores from the patient global assessment, as well as findings from an acute phase reactant (either C-reactive protein level or erythrocyte sedimentation rate). However, the clinically relevant cutoff values for disease activity states and improvement for this composite index had not yet been determined. The ASDAS was developed by the Assessment of Spondyloarthritis International Society (ASAS).
Dr. Machado and his colleagues performed ROC (receiver operating characteristic) analysis against several external criteria to determine the optimal cutoffs, using data from the large Norwegian disease-modifying antirheumatic drug (NOR-DMARD) registry. Included in the registry are data on patients with ankylosing spondylitis who started treatment with either a conventional DMARD or a tumor necrosis factor blocker. The investigators cross-validated those data with information from the ASSERT (Ankylosing Spondylitis Study for the Evaluation of Recombinant Infliximab Therapy) patient database.
ASAS members voted to define distinct disease activity states: inactive disease, and moderate, high, and very high disease activity. In the ROC analysis, both patient and physician global assessments at predefined levels were used as external constructs for inactive disease, to separate moderate from high disease activity, and for very high disease activity, respectively. ASAS partial remission was also used as a criterion for determining the cutoff for inactive disease. Based on these findings, the investigators established the following cutoff ASDAS scores for separating inactive disease, moderate, high, and very high disease activity: 1.3, 2.1, and 3.5, respectively.
Selected cutoffs for improvement scores were a change of at least 1.1 units for clinically important improvement, and a change of at least 2.0 units for major improvement, Dr. Machado explained.
The cutoff values then were validated in an 80% random sample of the 6-month ASSERT (n = 219). Findings showed a clear shift of treated patients from higher and toward lower disease activity states. Moreover, the longitudinal differences between the infliximab and placebo groups clearly discriminated between the two treatment arms.
“Results of our cross-validation strongly supported these cutoffs,” he said. The scores perform better than existing criteria for evaluating clinical disease activity and improvement. The ASDAS is a composite index with continuous measure ment properties that avoids redundancy and allows for more thorough evaluation of disease activity, he said.
Disclosures: Dr. Machado reported that he has received grant or research support in the form of a fellowship from ARTICULUM. Other researchers involved with this study reported receiving grant or research support from Centocor Inc. and/or serving as a consultant or employee for Centocor.
To see an interview with Dr. Machado, go to
Source Heidi Splete/Elsevier Global Medical Newswww.youtube/elsglobalmedicalnews