Background Recently, a Working Group of the SpondyloArtrhitis International Society (ASAS) has proposed a composite disease activity score, the Ankylosing Spondylitis Disease Activity Score (ASDAS), for patients with ankylosing spondylitis (AS), for improved and feasible measures of disease activity and treatment response in patients with spondyloarthritis (SpA) (1,2).
Objectives To evaluate the validity of ASDAS as a clinical tool for measurement of disease activity in early SpA in comparison with conventional clinical measures of disease activity. To assess the discriminative ability and correlation of the ASDAS and Bath Ankylosing Spondylitis Activity Disease Activity Index (BASDAI) with disease activity in early SpA.
Methods Patients with early SpA were selected from the ESPeranza database (n=603). The ASDAS (two versions) indices were applied in the ESPeranza cohort. To test concurrent validity of the indices, correlations (p value) of the two indices with disease activity variables were calculated in the ESPeranza database.
Patient and physician global scores were used as constructs of disease activity. Patients were categorised into high and low disease activity states based on patient and physician global assessment scores and the physician’s decision to start on a disease-modifying anti-rheumatic drug or tumour necrosis factor blocker. The discriminatory ability of the indices was compared using the approach of standardised mean difference between subgroups of patients with high vs. low disease activity.
Results 603 patients with early SpA were included in the study. ASDAS B and C showed good correlation with BASDAI (0.74 and 0.72, p<0.001). Both scores (ASDAS and BASDAI) correlated well with disease as reflected by the patient global assessment (BASDAI 0.71, ASDAS B 0.66, ASDAS C 0.66, p<0.001) and the physician global score (r=0.44 for BASDAI, r=0.44 for ASDAS B, r=0.48 for ASDAS C, p<0.001). CRP and ESR showed poor correlation with patient- and physician-derived disease activity scores (CRP 0.13 and 0.21, ESR 0.16 and 0.15, p<0.001). ASDAS and BASDAI scores showed similar good and moderate discriminative ability with different constructs of disease activity.
Conclusions ASDAS is a disease activity index valid in early Spa. ASDAS may be a useful tool for monitoring early SpA in clinical trials and clinical practice. There were no differences between the two ASDAS scores. ASDAS and BASDAI scores show similar good and moderate discriminative ability and correlation with different constructs of disease activity. ASDAS was not superior to BASDAI in its ability to discriminate between high and low disease activity states in early SpA.
Lukas C, Landewé R, Sieper J, Dougados M, Davis J, Braun J et al. Development of an ASAS-endorsed disease activity score (ASDAS) in patients with ankylosing spondylitis. Ann Rheum Dis 2009; 68:18-24.
van der Heijde D, Lie D, Kvein IT, Sieper J, Van der Bosch F, Listing J et al. ASDAS, a highly discriminatory ASAS-endorsed disease activity score in patients with ankylosing spondylitis. Ann Rheum Dis 2009; 68:1811-18.
Disclosure of Interest C. Fernández-Espartero Grant/Research support from: ESPeranza Program has been supported by Pfizer, E. de Miguel Grant/Research support from: ESPeranza Program has been supported by Pfizer, M. Fernández Prada Grant/Research support from: ESPeranza Program has been supported by Pfizer, M. Gobbo Grant/Research support from: ESPeranza Program has been supported by Pfizer, C. Martínez Grant/Research support from: ESPeranza Program has been supported by Pfizer, E. Loza Grant/Research support from: ESPeranza Program has been supported by Pfizer
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