How Is Non-radiographic Axial Spondyloarthritis Diagnosed?

Non-radiographic axial spondyloarthritis (nr-axSpA) is a rare, autoimmune arthritis that causes pain and stiffness in the spine and joints. It’s tricky to diagnose because it’s a “clinical diagnosis.” That means that there’s no single test that diagnoses it. So, how does a diagnosis get made? We’re here to explain. 

What is non-radiographic axial spondyloarthritis?

Nr-axSpA falls under a family of conditions called spondyloarthritis. It’s a condition that causes inflammation in the spine and joints, and sometimes other parts of the body too. It affects about 1.2 million people in the U.S. (slightly more women than men). It typically starts at a younger age (before age 45). It’s a chronic condition, but it’s treatable.

Experts aren’t exactly sure what causes nr-axSpA. Like many autoimmune conditions, they do know that it’s due to a combination of: 

• Genetic risk: something in your DNA that makes you more likely than others to get it one day

• A trigger: something from your environment that gets the immune system’s attention (like an infection)

Nr-axSpa is hard to diagnose because it’s “non-radiographic.” This is a technical way of saying there are no X-ray (radiograph) changes from the condition. To be specific, X-rays of the sacroiliac (SI) joints in the pelvis are normal.

How does non-radiographic axial spondyloarthritis differ from ankylosing spondylitis?

The short answer is that they’re really similar. The difference is that ankylosing spondylitis causes X-ray changes while nr-axSpA does not. They’re both in the spondyloarthritis family.

What kind of healthcare provider treats non-radiographic axial spondyloarthritis?

Rheumatologists treat nr-axSpa. They’re healthcare providers that specialize in autoimmune conditions and arthritis. It’s important to see a rheumatologist if possible, since they’re most experienced in prescribing medications for nr-axSpa, many of which are biologics. 

How do healthcare providers diagnose non-radiographic axial spondyloarthritis?

There is no single test that diagnoses nr-axSpA, so delays in diagnosis are common. A bit of detective work is required. Rheumatologists use clues from the following sources to determine if someone has nr-axSpA.

Symptoms 

All people with nr-axSpa have inflammatory back pain. This is a special kind of back pain that typically: 

• Starts before age 45

• Is present when you wake up in the morning

• Improves with exercise 

Other symptoms vary from person to person and may include:

• Fatigue

• Stiffness

• Decreased flexibility of the spine

• Tender, swollen joints

• Inflammation inside of the eye (iritis)

• Painful swelling of an entire finger or toe (dactylitis)

• Pain where tendons attach to bones, like the back of the heel (enthesitis)

• Pain with deep inhales (costochondritis)

Medical history

Certain medical conditions increase the likelihood of the diagnosis of nr-axSpA. Examples of these are inflammatory bowel disease, psoriasis, or psoriatic arthritis. A family history of ankylosing spondylitis or nr-axSpA increases the chance of nr-axSpA too. 

It’s important to note that a personal or family history of one of these conditions doesn’t mean you definitely have nr-axSpA, or that you’ll get it one day. They’re simply additional clues that nr-axSpA might be the correct diagnosis.

Tests

Certain positive tests increase the likelihood of nr-axSpA. 

One is the blood test for the HLA-B27 gene. The HLA-B27 gene is present in up to 8% of healthy people — and it is not a disease. However, if you have the HLA-B27 gene in addition to symptoms of nr-axSpA, the chances are much higher that nr-axSpA is the correct diagnosis. 

Imaging tests — like MRI of the SI joints or spine — can also help make the diagnosis. MRI may show inflammation that isn’t seen on X-rays. However, nr-axSpA can still be the correct diagnosis even when MRIs are normal.

Is non-radiographic axial spondyloarthritis treatable?

Yes. Several medications are FDA-approved to treat nr-axSpA, and more are on the way. For example:

• Cimzia

• Cosentyx

• Taltz

• Rinvoq

Of note, rheumatologists also often use the same treatments for ankylosing spondylitis to treat nr-axSpA, since they have many similarities. 

Is non-radiographic axial spondyloarthritis a serious condition?

It depends. Nr-axSpA is different for every person who has it. Some people have only mild symptoms, and the condition never progresses. On the other hand, some people have more severe symptoms. Almost half of people with nr-axSpA progress to having X-ray changes over the course of their lifetime.

Why trust our experts?

Written by:

Samantha C. Shapiro, MD

Samantha Shapiro, MD, is a board-certified rheumatologist and internist with expertise in autoimmune and inflammatory conditions. She founded the division of rheumatology at Dell Medical School at The University of Texas at Austin.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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