Fig. 1

Fibromyalgia (FM) in spondyloarthritis depending on the Assessment of the Spondyloarthritis International Society (ASAS) classification criteria and the arm fulfilled. FM+ fibromyalgia defined by the Fibromyalgia Rapid Screening Tool (FIRST) questionnaire (i.e., FIRST ≥5/6), XRay(+) radiographic sacroiliitis, MRI(+) magnetic resonance imaging sacroiliitis, CRP(+) abnormal C-reactive protein (i.e., ≥6 mg/L)