What Tests Can Diagnose Axial Spondyloarthritis?

Exam tests, blood tests, and imaging can all play a role

An axial spondyloarthritis diagnosis can be tricky because there isn't a single test for it. Healthcare providers must consider a person's history of symptoms, physical exam, and various blood and imaging tests.

It is less common than other back pain, sometimes causing an incorrect diagnosis for many years.

This article discusses signs you may have axial spondylarthritis and the tests that diagnose the condition.

Orthopedist bending a senior man's knee to test for axial spondyloarthritis

Luis Alvarez / Getty Images

Axial spondyloarthritis includes two conditions considered part of the same disease spectrum: ankylosing spondylitis (AS)—which is sometimes called radiographic axial spondyloarthritis—and non-radiographic axial spondyloarthritis.

AS is sometimes considered a more advanced form of axial spondyloarthritis, and some, but not all, who initially have non-radiographic axial spondyloarthritis eventually develop AS.

Signs You May Need an Axial Spondyloarthritis Assessment

On average, people with axial spondyloarthritis aren't diagnosed until seven to 10 years after their symptoms start. Part of the reason for delayed diagnosis may be because it is a less common cause of back pain and/or a lack of primary care providers' experience in diagnosing it.

Asking your healthcare provider for an axial spondyloarthritis evaluation may prove helpful if you experience the following symptoms:

  • Chronic back pain that started before age 45
  • Family history of axial spondyloarthritis
  • Back pain that came on slowly but steadily
  • Symptoms with little relief for more than three months
  • Back pain that improves with exercise but worsens after rest
  • Waking in the middle of the night with pain and stiffness
  • Pain that responds well to non-steroidal anti-inflammatory drugs (NSAIDs), like Advil (ibuprofen) 
  • Back stiffness in the morning that lasts 45 minutes or longer

Investigating Axial Spondyloarthritis

Around 19% of American adults ages 20–65 experience lower back pain; only 1% are eventually diagnosed with axial spondyloarthritis. 

If you have chronic lower back or buttock pain, you may want to ask your healthcare provider if axial spondyloarthritis is a possibility. They may be able to run additional tests that help provide diagnostic clues. Or, they might be able to refer you to a specialist, like a rheumatologist.

Health History and Physical Exam

Your healthcare provider can determine a diagnosis by gaining a better understanding of your medical history, including the nature of your back pain, and completing a physical examination. 

Medical History

Your healthcare provider will ask about other health conditions or medical issues you have to determine the cause of your symptoms and about your family history. Although a single, inherited gene doesn't cause axial spondyloarthritis, some genes seem to increase its risk.

Other health issues that may occur with axial spondyloarthritis and increase its diagnostic likelihood include:

Some who have axial spondyloarthritis may have symptoms they might not realize are connected to the condition. For instance, enthesitis (inflammation of the tissue that connects your tendons and bones) is common among those with axial spondyloarthritis and may cause pain at the back of your heel or the bottom of your foot.

Physical Exam

A standard physical exam can help verify and evaluate your symptoms.

Healthcare providers will likely test for pain in your back by turning and twisting your leg and knee. This can help identify if you have a problem with your sacroiliac joint (where the spine and pelvis meet), which is almost always affected in axial spondyloarthritis. However, these tests aren't always reliable and might point to a different problem with this joint.

In more severe cases of axial spondyloarthritis, you may have reduced your spine's mobility. To perform spinal mobility tests, your healthcare provider might ask you to stand straight against a wall with your heels, buttocks, and shoulders touching it. If your head can't also touch the wall, it may indicate decreased spinal mobility. 

However, spinal mobility tests aren't good indicators for people in earlier stages of the disease. Because people without axial spondyloarthritis also have flexibility limitations, these tests alone can't provide a diagnosis.

Blood Testing

Unfortunately, scientists haven’t identified a specific blood test that definitively diagnoses axial spondyloarthritis. However, specific blood tests are often helpful.

Genetic Markers

The most important genetic marker in testing for axial spondyloarthritis is HLA-B27. Several studies have found that 74–89% of people eventually diagnosed with axial spondyloarthritis test positive for the HLA-B27 gene mutation. It also appears that people who test positive for HLA-B27 are more likely to have earlier and more severe symptoms than those who don't.

However, testing positive for HLA-B27 doesn't guarantee you'll have axial spondylarthritis. About 6% of people in the United States are positive for HLA-B27, whereas only 1% have axial spondyloarthritis. This percentage is even lower in minorities, such as Hispanic and Black populations. Furthermore, you don't need the genetic mutation to be diagnosed with axial spondyloarthritis.

Inflammation Markers

Blood tests for inflammatory markers can also be helpful for diagnosis. These markers, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), show that inflammation is actively occurring in the body. Some people with axial spondyloarthritis have elevated inflammatory markers, which can help pinpoint a diagnosis.

However, half or less of people with axial spondyloarthritis have elevations in these markers, or other medical conditions may account for them, so inflammation markers alone can't provide a definitive diagnosis.

Imaging Tests

Imaging tests play a key role in diagnosing axial spondyloarthritis. They are also helpful in distinguishing between different manifestations of the condition.


If your healthcare provider suspects axial spondyloarthritis, they will likely start with an X-ray of the sacroiliac joint.

If the X-ray shows inflammation of the joint (sacroiliitis), it's a strong indicator of axial spondyloarthritis. In many cases, one additional clinical feature of axial spondyloarthritis is usually enough to diagnose it.

Sacroiliitis on X-ray

If an X-ray shows sacroiliitis, you have ankylosing spondylitis (radiographic axial spondyloarthritis). Non-radiographic axial spondyloarthritis doesn’t show sacroiliitis on an X-ray, which is where it gets its name.


If axial spondyloarthritis is suspected but hasn’t clearly appeared with an X-ray or other assessments, a magnetic resonance imaging (MRI) test may be the next step.

Because an MRI is a more sensitive test than an X-ray, it can sometimes pick up sacroiliitis that the X-ray may have missed. MRI results, along with a clinical assessment, can help determine a diagnosis.

CT Scans

Computed tomography (CT) scans of the sacroiliac joint aren’t a standard part of testing for axial spondyloarthritis. It’s not quite as good as an MRI regarding diagnosis. However, it may sometimes be helpful if MRI results aren’t clear or an MRI isn’t available.

Similar to an MRI, this test must be taken alongside other clinical assessments to reach a diagnosis.


An ultrasound of the sacroiliac joint isn’t helpful for diagnosing axial spondyloarthritis. However, it can sometimes offer your healthcare provider more information about your symptoms.  For example, it might pick up enthesitis that your healthcare provider couldn’t identify through other examination methods.

How to Prepare for Your Appointment

If you suspect you have axial spondyloarthritis, make a list of signs or symptoms and bring them to your healthcare provider's attention. Questions you might ask your healthcare provider include:

  • Are my back pain symptoms more consistent with inflammatory (brought on by an autoimmune disease that leads to excess inflammation) or mechanical (brought on by the movement of the spine) back pain?
  • Do I have other symptoms that might suggest axial spondyloarthritis?
  • Should I get an HLA-B27 blood test or other blood work?
  • Should I get an X-ray of my sacroiliac joint?
  • Can I have a referral to a rheumatologist?


Axial spondyloarthritis, which includes ankylosing spondylitis and non-radiographic axial spondyloarthritis, can’t be diagnosed with a single test.

To diagnose it, healthcare providers must consider your symptoms, other medical conditions and health history, physical exams, blood work, and imaging results. Physical maneuvers of the sacroiliac joint, spinal mobility tests, and ultrasound examinations of the entheses can help point to a diagnosis.

HLA-B27 and blood tests for inflammation may be helpful tests for some, although they aren’t definitive. Imaging tests, particularly X-rays and MRI, can help make a conclusive diagnosis alongside other clinical signs.

A Word From Verywell

Unfortunately, it can sometimes take years to get a correct diagnosis of axial spondyloarthritis. If you feel like your lower back pain might result from axial spondyloarthritis, discuss it with your healthcare provider. With more in-depth testing and assessment, you may be able to get the answers you need.

Frequently Asked Questions

  • Is axial spondyloarthritis genetic?

    Axial spondyloarthritis has a genetic element but isn’t purely a genetic condition. Scientists have studied many different genes which increase the risk of axial spondyloarthritis.

  • How difficult is it to diagnose axial spondyloarthritis?

    Axial spondyloarthritis is less straightforward to diagnose than other medical conditions because the diagnosis doesn’t rely on a single test. It is easier to diagnose in people with multiple clear-cut signs of the disease and may take longer to diagnose in people with more subtle symptoms.

  • When do axial spondyloarthritis symptoms typically appear?

    For most people with axial spondyloarthritis, symptoms begin before age 45. It’s common for symptoms to start in a person’s 20s, but it can happen before or after.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Ruth Jessen Hickman, MD
Ruth Jessen Hickman, MD, is a freelance medical and health writer and published book author.