FAQ: What is the difference between BASDAI and ASDAS?

In this FAQ video module, Amanda Mixon, PA-C, explains the difference between the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the Ankylosing Spondylitis Disease Activity Score (ASDAS), two validated tools used to assess disease activity in axial spondyloarthritis. She reviews how BASDAI uses six patient-reported questions to evaluate fatigue, spinal pain, peripheral joint symptoms, enthesitis-related tenderness, and morning stiffness, providing a quick and practical measure of a patient’s overall symptom burden. This episode also explores how ASDAS combines patient-reported symptoms with an objective marker of inflammation, such as C-reactive protein or erythrocyte sedimentation rate. Amanda discusses the established ASDAS disease activity categories, its ability to measure clinically important improvement, and its value in monitoring treatment response, predicting radiographic progression, and supporting clinical decision-making. She also explains why BASDAI scores may remain elevated because of factors beyond active inflammation, including structural damage, osteoarthritis, fibromyalgia, sleep disturbances, or mood disorders. Designed for rheumatology advanced practice providers, nurse practitioners, physician assistants, and clinicians caring for patients with axial spondyloarthritis or ankylosing spondylitis, this FAQ highlights why BASDAI and ASDAS should be viewed as complementary tools. BASDAI helps clinicians understand how the patient feels, while ASDAS adds objective evidence of inflammation to provide a more complete picture of disease activity. For more rheumatology education and clinical resources, visit RhAPP’s website, the RhAPP content rheum, or the RhAPP ACE app.