Ankylosing spondylitis (AS) is a chronic, progressive inflammatory disease that affects the joints and connective tissues in the spine and other areas of the body. Diagnosis of AS requires a combination of medical history, physical examination, laboratory tests, imaging tests, and possibly other tests.
The first test used to diagnose AS is a physical examination. During the physical examination, your doctor will look for signs of inflammation in your spine, such as stiffness and reduced range of motion. They may also check for signs of involvement in other areas, such as your eyes, lungs, and heart.
Your doctor may also order laboratory tests to look for markers of inflammation, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). These tests measure the rate at which red blood cells settle to the bottom of a tube and the level of CRP in your blood, respectively. An elevated ESR and CRP can indicate inflammation in the body.
Imaging tests, such as X-rays, MRIs, and CT scans, may also be used to diagnose AS. X-rays can show changes in the bones and joints of the spine, while MRIs and CT scans can provide a more detailed view of the spine and other affected areas.
Your doctor may also order genetic testing to look for specific genes associated with AS. These genes, known as HLA-B27, are found in approximately 95 percent of people with AS.
Finally, your doctor may order other tests, such as a urine test, to rule out other conditions that may have similar symptoms.
In summary, the first test used to diagnose ankylosing spondylitis is a physical examination. This is followed by laboratory tests, imaging tests, genetic testing, and other tests, if necessary.