Title

BASDAI cut-off values corresponding to ASDAS cut-off values
September 24, 2021
Citation: Rheumatology (Oxford). 2021 Sep 24 [Epub ahead of print]

OBJECTIVE To determine cut-off values of Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) that can discriminate the four disease activity states (inactive disease, moderate disease activity, high disease activity, and very high disease activity), separated by the validated Ankylosing Spondylitis Disease Activity Score (ASDAS) cut-off values (1.3, 2.1, and 3.5).
METHODS We included 333 patients with axial spondyloarthritis whose data on BASDAI and ASDAS-C reactive protein (ASDAS-CRP) were available. Receiver operating characteristic curve (ROC) analysis was performed to determine the BASDAI cut-off values that best corresponded to ASDAS-CRP cut-off values. The degree of agreement between disease activity states based on the BASDAI and ASDAS-CRP cut-off values was assessed using weighted kappa.
RESULTS Of the total 333 patients, 52 (15.6%), 190 (57.1%), 76 (22.8%), and 15 (4.5%) patients had inactive disease, moderate disease activity, high disease activity, and very high disease activity, respectively, according to the ASDAS-CRP. ROC analyses revealed that the BASDAI values 1.9 (area under the curve [AUC]: 0.948 [0.922-0.974]), 3.5 (AUC: 0.926 [0.887-0.966]), and 4.9 (AUC: 0.917 [0.837-0.996]) best corresponded to the ASDAS-CRP values 1.3, 2.1, and 3.5, respectively. The degree of agreement between disease activity states based on the BASDAI and ASDAS-CRP cut-off values was good (weighted kappa: 0.724, p<0.001).
CONCLUSION The BASDAI values 1.9, 3.5, and 4.9 corresponded to the ASDAS-CRP values 1.3, 2.1, and 3.5, respectively. These cut-off values could be useful in clinical studies and real-world practice for determining disease activity status when ASDAS-CRP is unavailable.