How Is Axial Spondyloarthritis Diagnosed?

Axial spondyloarthritis (axSpA) can be hard to diagnose. It might take a long time. Some people endure many doctor visits and tests over several years before they get an accurate diagnosis. The average time it takes for people with axSpA to get a diagnosis is 7 to 10 years.^1,2

Delays in diagnosis are a big challenge for people with axSpA. If you have axSpA and your doctor does not diagnose it right away, it may lead to more health problems. These can include damage to your bones and joints, worse physical function, and a lower quality of life.^1,2

The earlier you find out you have the disease, the better chance you have of preventing these problems. Treatment can help slow or stop the progression, so getting diagnosed early is crucial.¹

Types of axial spondyloarthritis

AxSpA is divided into 2 types: radiographic and non-radiographic:^2,3

• Radiographic axSpA (r-axSpA) – There is visible inflammation or damage on X-ray or magnetic resonance imaging (MRI). R-axSpA is also known as ankylosing spondylitis (AS).
• Non-radiographic axSpA (nr-axSpA) – Joints appear normal on imaging, but there are symptoms of axSpA.

You can have nr-axSpA and never develop AS. But nr-axSpA may eventually progress to AS.²

Diagnosis challenges

There are several challenges that make diagnosing axSpA difficult. First, the symptoms of axSpA can look like other conditions, such as rheumatoid arthritis (RA) or a back injury. Symptoms may include:^1,2,4

• Pain in the spine that gets better with activity
• Limited flexibility in the spine
• Pain in other parts of the body, such as the hip, heel, or shoulder
• Swelling in the fingers or toes known as "sausage digits"

Second, there is no definitive test for axSpA. Doctors must instead rely on a combination of things, such as:^1,2,4

• Signs and symptoms
• Medical history
• Family history
• X-ray and MRI tests
• Blood tests

Third, axSpA can be a progressive disease, meaning it can get worse over time. This can make it hard to diagnose early, when symptoms are less severe. Early symptoms like joint pain may not be visible on X-rays, and recognizing them can be difficult.^1,2

Other factors also can lead to a delay in diagnosis. These may include:⁴

• People's limited access to specialists
• Doctors' lack of knowledge about axSpA
• Symptoms being controlled by over-the-counter pain relievers, such as ibuprofen
• Tests' failure to show evidence of axSpA, like inflammatory or genetic markers in the blood

Diagnostic criteria for axSpA

Rheumatologists usually make axSpA diagnoses. These are specialists who focus on disorders of the joints, bones, and connective tissue. They may take symptoms, X-ray findings, and blood test findings into account when diagnosing axSpA.²

Using a specific criteria, your doctor can either diagnose axSpA or rule it out. Unfortunately, there is not one standard set of criteria.^2,4

Modified New York criteria

The most common way to diagnose axSpA is to use the modified New York criteria. It looks at 3 things:³

• Symptoms
• X-ray or MRI findings
• Blood test results

According to this criteria, there must be inflammation that shows up on an X-ray or MRI. There also must either be symptoms that last for at least 3 months or a blood test that is positive for certain biomarkers.^2,3

The genetic marker known as HLA-B27 is often found in people with AS. But not everyone who has AS will be positive for this marker.^2,3

ASAS criteria

The Assessment of SpondyloArthritis International Society (ASAS) criteria is a newer and better way to figure out if someone has axSpA. This criteria helps doctors diagnose axSpA even when there is no visible evidence on an imaging test.³

The ASAS criteria divides spondyloarthritis (SpA) diagnoses into 2 types:³

• Axial – affecting the spine
• Peripheral – affecting joints in the arms or legs

Your doctor may also use other, less common, sets of criteria to diagnose you. Try to be patient and keep working with your doctor even if they cannot give you a diagnosis right away. It can take a long time to find out whether you have axSpA. But getting an accurate and timely diagnosis is important. Effective treatment that begins quickly can help improve axSpA outcomes.²