Categorizing Disease Activity in Ankylosing Spondylitis: SASDAS vs ASDAS

The Simplified Ankylosing Spondylitis Disease Activity Score (SASDAS) showed a strong correlation with the Ankylosing Spondylitis Disease Activity Score (ASDAS) for continuous variables in a post hoc analysis of data from a randomized controlled trial of etanercept for axial spondyloarthritis. Researchers published their findings in The Journal of Rheumatology.

For the study, the SASDAS was calculated by the linear addition of the ASDAS components without adjustment and compared to the ASDAS for measuring and categorizing disease activity using data from the EMBARK trial.

The trial randomized patients with early axial spondyloarthritis to 50 mg of once-weekly etanercept or placebo over 12 weeks in a double-blind phase. Afterward, participants received open-label etanercept for 92 weeks.

The Spearman correlation coefficient determined very strong correlation between the ASDAS and SASDAS for continuous variables at baseline and during treatment, according to study authors. The SASDAS put 69.9% of patients in the same disease categories as the ASDAS for pooled categorical data at baseline, but it overestimated for 17.8% and underestimated for 12.2% of patients. Postbaseline data showed a similar pattern.

The ASDAS demonstrated better capacity to differentiate between treatment groups than the SASDAS. Sensitivity to change, nevertheless, was similar with both scores.

“A very strong correlation between the SASDAS and ASDAS was observed when considering continuous variables; however, moderate to substantial agreement was observed for categorical data,” researchers concluded, “and the SASDAS classified a lower proportion of patients as being in the inactive and low disease activity categories.”

Reference:
Schneeberger EE, Citera G, Ponce de Leon D, et al. Simplified Ankylosing Spondylitis Disease Activity Score (SASDAS) versus ASDAS: a post hoc analysis of a randomized controlled trial. J Rheumatol. 2022;jrheum.211075. doi:10.3899/jrheum.211075