Tests and diagnosis

By Mayo Clinic Staff

During the physical exam, your doctor may ask you to bend your back in different directions. He or she may also measure your chest circumference — once with your lungs empty and once with them full of air — to compare the difference.

Your doctor may also try to reproduce your pain by pressing on specific portions of your pelvis or by moving your legs into a particular position. He or she might also ask you to try to stand upright, with your heels and the back of your head against a wall.

Imaging tests

X-rays allow your doctor to check for changes in your joints and bones, though the visible signs of ankylosing spondylitis may not be evident early in the disease.

Magnetic resonance imaging (MRI) uses radio waves and a strong magnetic field to provide more-detailed images of bones and soft tissues. MRI scans can reveal evidence of ankylosing spondylitis earlier in the disease process, but are much more expensive.

Lab tests

There are no specific lab tests to identify ankylosing spondylitis. Certain blood tests can check for markers of inflammation, but inflammation can be caused by many different health problems. Your blood can be tested for the HLA-B27 gene, but most people who have that gene don't have ankylosing spondylitis.

Feb. 11, 2014