Purpose of review: Ankylosing spondylitis (AS) is characterized by inflammatory back pain, impaired spinal mobility, and sacroiliitis on radiographs. The diagnostic delay in AS of several years is mainly attributable to the late appearance of definite sacroiliitis on radiographs. Efforts have been made in recent years to improve and standardize making an early diagnosis.
Recent findings: MRI can visualize sacroiliitis in patients with typical symptoms of AS, that is inflammatory back pain, but yet normal radiographs of the sacroiliac joints, and has evolved as the most important diagnostic imaging tool in early disease, also referred to as nonradiographic axial spondyloarthritis (SpA). Both human leukocyte antigen-B27 and sacroiliitis on MRI play a major role in the recently proposed diagnostic algorithm which is meant to be applied in individual patients as well as in the new Assessment of SpondyloArthritis international Society (ASAS) classification criteria for axial SpA. Most recently, ASAS has also developed new criteria for peripheral SpA.
Summary: The new ASAS criteria for axial SpA will facilitate the conduct of clinical trials and other studies in early axial SpA and will help establishing a diagnosis. Yet, they should not be misused as diagnostic criteria. The new criteria for peripheral SpA may better reflect the current view on peripheral SpA.