page_title: Ankylosing spondylitis
section_title: Diagnosis
hierarchical_section_title: Ankylosing spondylitis / Diagnosis
caption_attribution_description: English: 34-year old male patient with confirmed AS (duration of inflammatory back pain 13 years, BASDAI 4.9, HLA B27 positive). Inflammatory lesions of the anterior chest wall are shown in the manubriosternal joint (curved arrows) on coronal (left) and sagittal (right) STIR images. Inflammatory changes are seen in the lower thoracic spine and L1 (arrows).
context_page_description: Ankylosing spondylitis is a type of arthritis in which there is a long-term inflammation of the joints of the spine. Typically the joints where the spine joins the pelvis are also affected. Occasionally other joints such as the shoulders or hips are involved. Eye and bowel problems may also occur. Back pain is a characteristic symptom of AS, and it often comes and goes. Stiffness of the affected joints generally worsens over time.
  Although the cause of ankylosing spondylitis is unknown, it is believed to involve a combination of genetic and environmental factors. More than 85% of those affected in the UK have a specific human leukocyte antigen known as the HLA-B27 antigen. The underlying mechanism is believed to be autoimmune or autoinflammatory. Diagnosis is typically based on the symptoms with support from medical imaging and blood tests. AS is a type of seronegative spondyloarthropathy, meaning that tests show no presence of rheumatoid factor antibodies. It is also within a broader category known as axial spondyloarthritis.
  There is no cure for ankylosing spondylitis. Treatments may improve symptoms and prevent worsening.
context_section_description: Ankylosing spondylitis is a member of the more broadly defined disease axial spondyloarthritis. Axial spondyloarthritis can be divided into (1) radiographic axial spondyloarthritis (which is a synonym for ankylosing spondylitis) and (2) non-radiographic axial spondyloarthritis (which include less severe forms and early stages of ankylosing spondylitis) 
  While ankylosing spondylitis can be diagnosed through the description of radiological changes in the sacroiliac joints and spine, there are currently no direct tests (blood or imaging) to unambiguously diagnose early forms of ankylosing spondylitis (non-radiographic axial spondyloarthritis). Diagnosis of non-radiologic axial spondyloarthritis is therefore more difficult and is based on the presence of several typical disease features.
  These diagnostic criteria include:
  Inflammatory back pain:
  Chronic, inflammatory back pain is defined when at least four out of five of the following parameters are present: (1) Age of onset below 40 years old, (2) insidious onset, (3) improvement with exercise, (4) no improvement with rest, and (5) pain at night (with improvement upon getting up)
  Past history of inflammation in the joints, heels, or tendon-bone attachments
  Family history for axial spondyloarthritis or other associated rheumatic/autoimmune conditions
  Positive for the biomarker HLA-B27
  Good response to treatment with nonsteroidal anti-inflammatory drugs (NSAIDs)
  Signs of elevated inflammation (C-reactive protein and erythrocyte sedimentation rate)
  Manifestation of psoriasis, inflammatory bowel disease, or inflammation of the eye (uveitis)
  If these criteria still do not give a compelling diagnosis magnetic resonance imaging (MRI) may be useful. MRI can show inflammation of the sacroiliac joint.
caption: 34-year-old male with AS. Inflammatory lesions of the anterior chest wall are shown (curved arrows). Inflammatory changes are seen in the lower thoracic spine and L1 (arrows).
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