Ankylosing Spondylitis Tests: How Doctors Diagnose The Condition

Maybe your like

HealthlineSubscribeExplore more in Ankylosing Spondylitis

Physical exam for ankylosing spondylitis

Your doctor will likely start the diagnostic process by considering your medical history and family history as well as performing a physical exam.

During your exam, your doctor may ask you the following questions to help rule out other conditions:

How long have you had symptoms?
Do your symptoms get better with rest or exercise?
Are your symptoms getting worse or staying the same?
Are your symptoms worse at a particular time of day?

Your doctor will check for limitations in your mobility and look for tender areas. Many conditions can cause similar symptoms, so your doctor will check to see if your pain or lack of mobility are consistent with the most typical signs of ankylosing spondylitis.

The hallmark sign of ankylosing spondylitis is pain and stiffness of your sacroiliac joints. Your sacroiliac joints are located in your lower back where the base of your spine and pelvis meet.

Other conditions that your doctor will try to rule out include:

back pain caused by sudden injuries, poor posture, or awkward sleeping position
lumbar spinal stenosis
rheumatoid arthritis
psoriatic arthritis
diffuse idiopathic skeletal hyperostosis

Specific physical tests your doctor may perform include the following:

Chest expansion

Ankylosing spondylitis can limit your ability to breathe in fully if your mid-spine or ribs are affected. Your doctor will likely check to see if you can expand your chest as much as would be expected for your age and gender.

Schober test

The Schober test is commonly used to test your degree of lumbar flexion when you bend forward. Limited flexion of your lower back is a common sign of ankylosing spondylitis. Lateral flexion is also tested.

During the Schober test, your doctor will draw lines on your lower back and measure the distance between the lines when you bend forward.

Gaenslen test

The Gaenslen test is commonly used to search for pain and inflammation in your sacroiliac joint. During this test, you’ll lie on your back with a knee pulled to your chest and your opposite leg dangling off the table. Your doctor will put pressure on your opposite leg to see if you experience pain in your joint.

Neurological exam

Your doctor will likely also perform a neurological exam to rule out nerve conditions that affect your muscle strength and reflexes. They’ll also review whether you have other symptoms such as poor bladder and bowel function that could indicate a problem such as a herniated disc.

Blood tests used to diagnose ankylosing spondylitis

Blood tests can help rule out other conditions and check for signs of inflammation suggestive of ankylosing spondylitis. Blood tests alone can’t provide enough evidence to diagnose ankylosing spondylitis, but they can provide supportive evidence along with the results of imaging tests.

It usually only takes about a day or two to get the results of your blood tests.

Your doctor may order one of the following blood tests:

C-reactive protein (CRP) test. A CRP test checks your levels of CRP, which is a protein associated with inflammation in your body.
Erythrocyte sedimentation rate (ESR test). A ESR test measures inflammation in your body by calculating the rate that your red blood cells settle to the bottom of a blood sample.
Complete blood count (CBC). A CBC checks your red and white blood cell counts. Increased levels of white blood cells or low levels of red blood cells can indicate inflammation associated with ankylosing spondylitis.

Genetic testing for ankylosing spondylitis

A genetic blood test may also be used to see if you carry the HLA-B27 gene. About 7 percent of Americans have this gene, but it’s found in 90 to 95 percent of people with definite ankylosing spondylitis.

Testing positive for this gene doesn’t mean you have ankylosing spondylitis. Only about 5 to 6 percent of people who carry this gene go on to develop ankylosing spondylitis. But if you carry the HLA-B27 gene, your doctor is more likely to expect that you have the condition. This gene is also connected to an eye inflammation condition (uveitis).

Imaging tests for ankylosing spondylitis

Imaging tests can examine commonly affected areas such as your spine and pelvis to look for signs of anklyosing spondylitis such as:

joint fusion
erosion
extra bone formation (syndesmophyte and osteophyte)
calcification

X-rays

X-rays are the most commonly used imaging technique. However, changes to your joints aren’t often visible in the early stages of the disease. According to the Spondylitis Association of America, it can take 7 to 10 years for noticeable changes to appear.

MRIs

If your doctor still suspects ankylosing spondylitis even if X-rays come back negative, they may recommend that you undergo magnetic resonance imaging (MRI).

Researchers are still examining whether ultrasounds are useful for diagnosing or monitoring ankylosing spondylitis.

Confirming diagnosis of ankylosing spondylitis

Usually, a diagnosis can be confirmed when X-rays or MRIs show inflammation of your sacroiliac joint and at least one of the following are true:

you have limited chest expansion for your demographic
you have limited range of motion in your lower back
your back pain hasn’t improved within 3 months, it tends to feel better with exercise, and it gets worse with rest

Next steps

Once you receive a diagnosis for ankylosing spondylitis, you can work with your doctor to develop a treatment plan.

There’s no cure, but a combination of exercise, physiotherapy, and medications can help you manage pain and stiffness and keep your condition from getting worse.

Non-steroidal anti-inflammatory drugs are often the first-line medication. If they don’t control the inflammation, your doctor will recommend other medications such as:

tumor necrosis factor inhibitors
interleukin-17 inhibitors
disease-modifying antirheumatic drugs
steroid injections

Additional resources

Along with talking to your doctor, educating yourself on treatment options and lifestyle changes may help you manage your condition. Here are additional resources you may find helpful:

Doctor Discussion Guide: Treating Ankylosing Spondylitis
10 Self-Care Tips for Living Well with Ankylosing Spondylitis
8 Tips for a Better Night’s Sleep When You Have Ankylosing Spondylitis
Fun Activities to Take Your Mind off Ankylosing Spondylitis Pain
Most Effective Ankylosing Spondylitis Exercises

How we reviewed this article:

SourcesHistoryHealthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Ankylosing spondylitis. (2019).https://www.nhs.uk/conditions/ankylosing-spondylitis/diagnosis/
Ankylosing spondylitis. (2017).https://labtestsonline.org/conditions/ankylosing-spondylitis
C-reactive protein (CRP). (2021).https://labtestsonline.org/tests/c-reactive-protein-crp
Líška D, et al. (2021). Clinical examination of the sacroiliac joint.https://journals.sagepub.com/doi/full/10.1177/22104917211000755
Overview of ankylosing spondylitis. (n.d.).https://spondylitis.org/about-spondylitis/types-of-spondylitis/ankylosing-spondylitis/
Stolwijk C, et al. (2014). Comparison of tests for lumbar flexion and hip function in patients with and without axial spondylarthritis.https://onlinelibrary.wiley.com/doi/full/10.1002/acr.22464
Wenker KJ, et al. (2021). Ankylosing spondylitis. (2021).https://www.ncbi.nlm.nih.gov/books/NBK470173/

Share this article

Medically reviewed by Nancy Carteron, M.D., FACR, Rheumatology - Immunology — Written by Daniel Yetman on October 22, 2021

Health Conditions

Condition Spotlight

Wellness Topics

Product Reviews

Featured Programs

Featured

Lessons

Newsletters

Lifestyle Quizzes

Health News

This Just In

Top Reads

Video Series

Find Your Bezzy Community

Follow us on social media

Related Topics

Management

Related Articles

Diet

Related Articles

Symptoms

Related Articles

Home Remedies

Related Articles

Stages

Related Articles

Related Conditions

Related Articles

Prognosis

Related Articles

Surgery

Related Articles

Treatment

Related Articles

Types

Related Articles

Physical exam for ankylosing spondylitis

Chest expansion

Schober test

Gaenslen test

Neurological exam

Blood tests used to diagnose ankylosing spondylitis

Genetic testing for ankylosing spondylitis

Imaging tests for ankylosing spondylitis

X-rays

MRIs

Confirming diagnosis of ankylosing spondylitis

Next steps

Additional resources

How we reviewed this article:

related stories

Read this next

Contact