How Axial Spondyloarthritis Is Diagnosed

To diagnose axial spondyloarthritis (axSpA), a healthcare provider will usually start by asking about your symptoms and medical history. They will do a physical exam to assess your pain and mobility in the spine, pelvis, and hips. Blood tests and imaging scans are also usually part of the workup, as well.

This article discusses the typical steps and tests involved in diagnosing axSpA.

Types of axSpA

There are two main types of axSpA:

• Ankylosing spondylitis (AS): A form of arthritis that causes chronic spine inflammation and pain in the back and hips. Imaging tests are able to detect damage to bones and/or joints caused by AS. 
• Non-radiographic axial spondyloarthritis (nr-axSpA): This diagnosis is given when a person has ankylosing spondylitis symptoms but no damage to bones or joints is detected on imaging tests, such as MRIs or X-rays.

Nearly 1.5 million Americans live with axSpA. Most are diagnosed before the age of 45, with the average onset of symptoms beginning at 28 years old.

An early and accurate diagnosis is essential in order to receive timely and effective treatment and improve long-term outcomes. Nearly half of people diagnosed with axSpA wait five or more years for a diagnosis, which can lead to irreversible damage to the spine caused by inflammation. In some people, nr-axSpA may progress to ankylosing spondylitis. 

If you’ve had chronic back pain (three months or more), it’s important to see a healthcare professional. Your primary care physician or a rheumatologist will review your symptoms, give you a physical examination, and use a combination of blood work and imaging tests to give a diagnosis and identify which form of axSpA you may have.

Checking Symptoms

There are no self-exams or at-home tests to diagnose axial spondyloarthritis. However, knowing the signs of axSpA can help prepare you to detect symptoms. Communicating any noticeable symptoms to your healthcare provider increases your chances of getting an early and accurate diagnosis.

Common symptoms of axial spondyloarthritis include: 

• Chronic back pain: Slow-onset, persistent back pain is often the first symptom of axSpA. You may notice the pain is more intense in the mornings or after a period of rest and can be relieved with movement, such as stretching or walking.
• Fatigue: Chronic pain often leads to physical and mental exhaustion. Pain can often disrupt sleep, which may leave you feeling more fatigued than usual during daytime hours.
• Heel pain: Sharp, stabbing pains in your heel or sole of the foot caused by inflammation is known as plantar fasciitis. Nearly 17% of people with axSpA also experience heel pain.
• Enthesitis: Enthesitis is inflammation in the body where tendons and ligaments attach to the bone. Many people with axSpA experience pain in their feet, hips, and knees due to enthesitis.
• Eye inflammation: Eye pain, blurred vision, and sensitivity to light are associated with axSpA. Eye inflammation tends to come on suddenly and may last anywhere from a few weeks to three months. 
• Joint pain: With inflammatory arthritis like axSpA, inflammation may affect all joints in the body, particularly the hips, pelvis, knees, and ankles. 
• Abdominal pain/diarrhea: Abdominal pain and diarrhea can be a symptom of inflammation in the gut. One study found that 30% of people with axSpA also had irritable bowel syndrome, which is associated with gastrointestinal discomfort, diarrhea, and the frequent urge to empty the bowels.

Physical Examination 

When you visit your healthcare provider or a rheumatologist for a diagnosis, they will begin with a review of your medical history, symptoms, and risk factors (e.g., family history) for axial spondyloarthritis. This will be followed by a physical examination.

During the physical exam, your healthcare provider will assess your mobility and look for joint inflammation in your spine, pelvis, and hips. They may ask you to move your body in certain ways (for example, reach for your toes, lift up your leg while lying down, put your chin to your chest) to determine how much your mobility has been affected and if those movements cause you pain.

They may also do a neurologic evaluation to assess your sensory and motor functions, including your reflexes and muscle strength.  

Labs and Tests 

There are some blood tests that may indicate if a person has axial spondyloarthritis. These blood tests will look for: 

• Inflammation markers: Blood tests can detect inflammatory markers that indicate inflammation in the body. Tests may detect erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) levels, and plasma viscosity (PV) levels, all of which are common markers for inflammation.
• Genetics: A family history of axial spondyloarthritis is a risk factor for developing the disease. Blood tests can determine if you carry the HLA-B27 gene. The association of the gene with axSpA varies among different ethnic groups. More than 95% of White people with axSpA carry the gene, whereas only 80% of people from Mediterranean countries and only 50% of Black people with axSpA are HLA-B27 positive.

Though blood tests alone can't provide enough evidence to diagnose axial spondyloarthritis, these blood markers can help healthcare providers get an idea of your risk factors. 

Imaging 

In order to give an accurate diagnosis of axial spondyloarthritis, your healthcare provider will need to order imaging tests to see if axSpA has affected your spine and joints. These include:

• X-rays: X-rays are the standard imaging test healthcare providers will use to look for bone damage in your spine and sacroiliac joint. Along with indicating bone damage, X-ray images may show where joint space is getting wider or more narrow, and detect bone fusions. Bone damage can be detected only in people with ankylosing spondylitis. X-rays will not detect any damage to the bones and joints in people with non-radiographic axial spondyloarthritis (nr-axSpA).
• Computed tomography (CT) scan: CT scans produce detailed images of internal parts of the body, including organs and bones. For an axSpA diagnosis, they are used to detect structural changes in the bone, such as bone erosion or new bone formation/fusion.
• Magnetic resonance imaging (MRI): MRIs send radio waves through the body to produce images of the body’s soft tissues. MRIs can detect inflammation in the body before any damage to the joints or bones has occurred. It is particularly effective at detecting axSpA in the earlier stages of the disease. If you have nr-axSpA, an MRI may show inflammation in the soft tissues around your spine and sacroiliac joint. 

When reviewing the images, your healthcare provider and radiologist will look for signs of:

• “Bamboo spine” (spinal joints fusing together to form what looks like one long bone)
• Erosion (wearing away) or thickening of fibrous tissues around the joints, particularly where the spine meets the pelvis
• Bone calcification
• Loss of cartilage between the joints 
• Presence of abnormal kyphosis (humpback) 
• Spinal fractures 

Differential Diagnoses

Axial spondyloarthritis can be difficult to diagnose. Some people with axSpA are initially misdiagnosed with another condition, such as: 

• Fibromyalgia: A chronic pain disorder associated with musculoskeletal pain throughout the body, fatigue, brain fog, and emotional distress. Nearly 4 million adults in the United States are diagnosed with fibromyalgia, and women are two times more likely to be affected than men.
• Chronic back pain: Though it is the first and most prevalent symptom of axSpA, chronic back pain is also a stand-alone diagnosis with a number of different causes. It is often caused by something mechanical, meaning there’s an injury in a part of the back, such as the spine, muscle, discs, or nerves.  
• Enteropathic arthritis: An inflammatory condition that affects the spine and other joints. It commonly occurs in individuals with irritable bowel syndrome and Crohn’s disease. Symptoms include back pain and stiffness similar to that experienced with axSpA.
• Diffuse idiopathic skeletal hyperostosis (DISH): A type of arthritis that causes tendons and ligaments around the spine to harden, causing pain, stiffness, and reduced range of motion. This skeletal disorder can also cause new and unusual bone formation on the spine and around other joints in the body.

When you see your healthcare provider, communicate your symptoms clearly and openly. Share your medical history and family history, particularly if you have a family history that includes axSpA or other forms of arthritis.

If your primary healthcare provider is unfamiliar with axSpA, seek the help of a specialist, such as a rheumatologist.

Summary

Axial spondyloarthritis is a rheumatological condition that affects the spine and axial joints. It can be diagnosed through physical examinations, imaging tests, and certain blood tests. Because chronic back pain is a primary symptom of axSpA, it's very possible for the condition to be misdiagnosed.

A Word From Verywell 

If you’ve been experiencing persistent, ongoing back pain, speak with your healthcare provider. Early detection of axial spondyloarthritis is key to receiving treatment and preventing further damage to your bones and joints. Living with chronic pain can be difficult, but early intervention and treatment can help reduce your pain and inflammation and improve your overall quality of life.