Fig. 3

ASAS modification of the Berlin diagnostic algorithm for axSpA [22].* AS = ankylosing spondylitis; axSpA = axial spondyloarthritis; CRP = C-reactive protein; ESR = erythrocyte sedimentation rate; HLA = human leukocyte antigen; IBD = inflammatory bowel disease; MRI = magnetic resonance imaging; nr-axSpA = nonradiographic axial spondyloarthritis; NSAID = nonsteroidal anti-inflammatory drug; SpA = spondyloarthritis. * The algorithm is intended for use by rheumatologists for patients in the specified age range and not in an unselected population of patients with chronic back pain. ^† The modified New York criteria for sacroiliitis are: grade ≥ 2 bilaterally or grade ≥ 3–4 unilaterally [13]. ^‡ Active acute inflammation is defined by clearly present bone marrow edema (on short-T1 inversion recovery) or osteitis (on T1 post gadolinium) highly suggestive of SpA, located in subchondral or periarticular bone marrow [15]