Axial spondyloarthritis – Diagnostics – Overview of Information and Clinical Research

Diagnosing axial spondyloarthritis requires a careful combination of physical examination, blood tests, and imaging studies to identify inflammation in the spine and related joints. Because symptoms often begin in young adults and can resemble common back pain, finding the right diagnosis may take time and the expertise of a specialist called a rheumatologist.

Introduction: When to Seek Diagnostic Testing

If you’re experiencing back pain that started before age 45 and has lasted for more than three months, it may be time to consider testing for axial spondyloarthritis. This is especially important if your pain has certain distinctive qualities that set it apart from ordinary back problems. Many people with axSpA notice that their discomfort develops slowly over weeks or months rather than appearing suddenly after an injury or strain.^[1]

The pattern of your pain can offer important clues. If your back stiffness is particularly severe when you first wake up in the morning, or if your pain actually feels better when you move around and exercise rather than when you rest, these are signs that warrant medical attention. Similarly, if the discomfort worsens at night or during periods of inactivity, or if it spreads to your hips or buttocks, seeking diagnostic evaluation becomes even more important.^[1]

Young adults, including teenagers and people in their twenties, should be especially attentive to these symptoms. Axial spondyloarthritis typically begins during this stage of life, though anyone can develop the condition. The disease affects about 1 in 100 people worldwide and occurs equally in males and females, though certain forms may be more visible in one gender than another.^[1]^[6]

Beyond back pain, there are other symptoms that should prompt you to seek diagnostic testing. Some people with axSpA experience inflammation in other parts of their body, which may seem unrelated to joint problems at first. Eye inflammation called uveitis (which is when the inside of the eye becomes inflamed) can cause eye pain, redness, and sensitivity to light. Digestive problems such as diarrhea, skin conditions like psoriasis (a condition that causes red, scaly patches on the skin), or swelling in your fingers, toes, or heels may also occur alongside back symptoms.^[1]^[2]

⚠️ Important

If you have persistent back pain lasting more than three months that improves with movement but worsens with rest, especially if you’re under 45 years old, speak with a healthcare provider about testing for axial spondyloarthritis. Early diagnosis can help prevent long-term complications and preserve your spine’s flexibility.

Classic Diagnostic Methods

Physical Examination and Medical History

The diagnostic journey for axial spondyloarthritis typically begins with a thorough physical examination performed by a healthcare provider, often a specialist in joint and inflammatory diseases called a rheumatologist (a doctor who specializes in diseases of the joints, muscles, and bones). During this examination, your doctor will check your vital signs, which include basic measurements like blood pressure, heart rate, and temperature. These provide general information about your overall health status.^[1]

Your medical history plays a crucial role in diagnosis. Your doctor will ask detailed questions about the characteristics of your pain, when it started, what makes it better or worse, and how it affects your daily activities. They’ll want to know if anyone in your family has had similar problems, since axial spondyloarthritis often runs in families. The specialist will also ask about other symptoms you may be experiencing in different parts of your body, such as your eyes, skin, or digestive system.^[1]^[7]

During the physical exam, your doctor will assess your spine’s flexibility and range of motion. They may ask you to bend forward, backward, and to the sides to see how easily your spine moves. They’ll also examine specific joints, particularly where your spine connects to your pelvis, an area called the sacroiliac joints (the joints that connect the bottom of your spine to your hip bones). Tenderness or limited movement in these areas can suggest inflammation typical of axSpA.^[3]

Blood Tests

Blood tests are an important part of the diagnostic process, though they alone cannot confirm axial spondyloarthritis. Your healthcare provider will likely order several different blood tests to look for signs of inflammation and genetic markers associated with the condition.^[1]

One of the most commonly tested markers is the HLA-B27 gene (a genetic marker often found in people with axial spondyloarthritis). Most people with axSpA carry this gene, and testing positive for it can support a diagnosis. However, the relationship between this gene and the disease is not straightforward. Many people who have the HLA-B27 gene never develop axSpA, and some people with the condition don’t have the gene at all. Therefore, having this gene doesn’t mean you will definitely get the disease, and not having it doesn’t rule the disease out.^[1]^[2]

Another blood test looks for C-reactive protein (a substance in your blood that increases when there is inflammation in your body), often abbreviated as CRP. When inflammation is present anywhere in your body, levels of this protein rise in your bloodstream. Elevated CRP levels can indicate that inflammation is occurring, which supports the diagnosis of an inflammatory condition like axSpA. However, not everyone with axSpA has elevated CRP, so normal levels don’t exclude the diagnosis.^[1]

Similar to CRP, doctors may also check your erythrocyte sedimentation rate (a test that measures how quickly red blood cells settle in a tube, which can indicate inflammation), or ESR, which is another marker of inflammation. These tests help build a complete picture but must be interpreted alongside other findings.^[7]

Imaging Tests

Imaging studies are essential for diagnosing axial spondyloarthritis because they allow doctors to see inflammation or damage in your spine and related joints that cannot be detected through physical examination alone. Two main types of imaging are used: X-rays and MRI scans.^[1]

X-rays of the spine and pelvis have traditionally been the standard imaging method for diagnosing axSpA. They can show structural changes in the bones, particularly in the sacroiliac joints where the spine meets the pelvis. When inflammation has been present for some time, it can cause visible damage on X-rays, a condition called sacroiliitis (inflammation of the sacroiliac joints visible on X-rays). When these changes are clearly visible on X-rays, doctors may diagnose the condition as ankylosing spondylitis (a form of axial spondyloarthritis where bone damage can be seen on X-rays), which is also called radiographic axial spondyloarthritis.^[1]^[2]^[3]

However, X-rays have an important limitation. They can only show damage that has already occurred to the bones, which may take months or even years to develop. In the early stages of the disease, inflammation may be active and causing symptoms, but no bone changes are visible yet on X-rays. This means that a normal X-ray doesn’t necessarily mean you don’t have axial spondyloarthritis.^[7]^[8]

This is where magnetic resonance imaging, or MRI, becomes particularly valuable. MRI scans use powerful magnets and radio waves to create highly detailed images of your body’s soft tissues. Unlike X-rays, MRI can detect inflammation in the spine and sacroiliac joints much earlier, often years before any bone damage appears. This makes MRI especially useful for diagnosing people who have symptoms of axSpA but whose X-rays appear normal.^[1]^[2]

When someone has the symptoms and other signs of axial spondyloarthritis but their X-rays don’t show bone changes, doctors may diagnose non-radiographic axial spondyloarthritis (a form of axial spondyloarthritis where X-rays don’t show bone damage, but symptoms and possibly MRI show inflammation), often abbreviated as nr-axSpA. About 7 in 10 people with nr-axSpA will have visible inflammation on MRI, even though their X-rays look normal. Interestingly, about 3 in 10 people with nr-axSpA may not even have inflammation visible on MRI despite having symptoms. The reasons for this are not fully understood and may relate to the sensitivity of MRI technology or the timing of when the scan is performed.^[4]^[8]

It’s important to understand that radiographic and non-radiographic axial spondyloarthritis are not separate diseases. They exist on a spectrum of the same condition. Someone with nr-axSpA may eventually develop visible changes on X-rays and be reclassified as having ankylosing spondylitis, though not everyone progresses in this way. Both forms cause real symptoms and require proper treatment.^[7]^[8]

Distinguishing AxSpA from Other Conditions

One of the challenges in diagnosing axial spondyloarthritis is that back pain is extremely common, and most back pain is not caused by inflammatory arthritis. Many people visit general practitioners, orthopedists, and physiotherapists with complaints of chronic lower back pain that may be due to non-specific mechanical problems, such as muscle strain, herniated discs, or age-related wear and tear. These conditions are usually far more common than axSpA.^[7]

Doctors use several features to distinguish inflammatory back pain from mechanical back pain. Unlike mechanical pain, inflammatory back pain typically starts gradually, improves with exercise, worsens with rest, is accompanied by significant morning stiffness lasting more than 30 minutes, and often wakes you up in the second half of the night. The pain in axSpA is also chronic, meaning it persists for at least three months, and usually begins before age 45.^[3]^[7]

The diagnostic process involves carefully considering all the information together: your symptoms, the results of your physical examination, blood test findings, and imaging results. Only by looking at this complete picture can doctors accurately diagnose axial spondyloarthritis and distinguish it from other causes of back pain.^[1]

Diagnostics for Clinical Trial Qualification

When researchers conduct clinical trials to test new treatments for axial spondyloarthritis, they need to use standardized criteria to decide which patients can participate. These criteria ensure that all participants truly have the condition being studied and that results can be reliably compared across different studies.^[7]

The most widely used classification criteria for clinical trials come from an international group called the Assessment of SpondyloArthritis international Society, abbreviated as ASAS. In 2009, ASAS developed specific criteria for classifying axial spondyloarthritis that have become the standard for research studies.^[7]

To qualify for most clinical trials, participants must first have chronic back pain that has lasted for at least three months and started before age 45. This is the fundamental symptom that prompts further evaluation. Beyond this basic requirement, patients must meet additional criteria that fall into two main categories: imaging findings and clinical features.^[7]

On the imaging side, trial enrollment often requires evidence of sacroiliitis (inflammation or damage in the sacroiliac joints) visible on X-rays or MRI. For X-rays, there are specific grading systems that define what degree of change qualifies as definite sacroiliitis. For MRI, researchers look for active inflammation in the sacroiliac joints or spine. Having this imaging evidence is often essential for enrollment in studies of radiographic axial spondyloarthritis or ankylosing spondylitis.^[7]

For studies enrolling patients with non-radiographic axial spondyloarthritis, the requirements may be slightly different. These trials might accept patients whose X-rays are normal or show only minimal changes, as long as there are other strong indicators of the disease. This could include a positive HLA-B27 gene test combined with several clinical features typical of axSpA, such as inflammatory back pain, pain in the buttocks that alternates from side to side, inflammation of tendons where they attach to bone (called enthesitis), eye inflammation, psoriasis, or inflammatory bowel disease.^[7]^[8]

Blood tests play an important role in trial qualification. Most studies require documentation of the HLA-B27 gene status, as this is part of the diagnostic criteria. Some trials also measure inflammatory markers like C-reactive protein or erythrocyte sedimentation rate to confirm that active inflammation is present. In some cases, trials specifically seek patients with elevated inflammatory markers because these individuals may respond differently to certain treatments.^[1]^[7]

Clinical trials also use various assessment tools to measure disease activity and determine if someone’s condition is severe enough to warrant enrollment. One common tool is the Bath Ankylosing Spondylitis Disease Activity Index, or BASDAI, which uses patient-reported information about pain, stiffness, and fatigue to calculate a disease activity score. Trials often require participants to have a BASDAI score above a certain threshold, typically 4 or higher on a scale of 0 to 10, to ensure they have active disease that might benefit from the treatment being studied.^[19]

Physical function is evaluated using measures like the Bath Ankylosing Spondylitis Functional Index, or BASFI, which assesses how well people can perform daily activities despite their condition. Similarly, spinal mobility may be measured using specific tests that evaluate how far you can bend forward or how much your spine can move in different directions. These objective measurements help researchers track whether a treatment is making a meaningful difference.^[19]

Many clinical trials also have exclusion criteria based on diagnostic findings. For example, trials might exclude people who have previously taken certain medications, those with evidence of other autoimmune diseases, or individuals with abnormal blood test results that suggest other health problems. Imaging studies are carefully reviewed to ensure that bone damage or other changes are consistent with axSpA and not caused by other conditions like osteoarthritis or previous injuries.^[7]

The diagnostic procedures used in clinical trials are often more extensive than what you might experience during routine care. Researchers need detailed baseline information to accurately measure how well a treatment works. This means trial participants typically undergo comprehensive blood testing, detailed imaging studies, and thorough physical examinations at the start of the study. These same tests are then repeated at regular intervals throughout the trial to track changes over time.^[10]

⚠️ Important

Participating in clinical trials requires meeting specific diagnostic criteria that may be stricter than those used for regular diagnosis. If you’re interested in joining a trial, your rheumatologist can help determine if you meet the requirements. Remember that trial participation is voluntary and your standard care will continue regardless of whether you choose to participate.

Prognosis and Survival Rate

Prognosis

The outlook for people with axial spondyloarthritis has improved significantly with advances in treatment over recent decades. With appropriate care, most people with axSpA can lead normal, productive lives and have a normal lifespan.^[3] However, the course of the disease can vary considerably from person to person.

Without treatment, axSpA can progressively affect your spine’s flexibility and function. Over time, ongoing inflammation can lead to new bone formation in the spine. This process, when severe, can cause individual vertebrae (the small bones that make up your spine) to fuse together, a condition called ankylosis. This fusion makes the spine less flexible and can lead to a hunched forward posture. The fusion process usually begins at the base of the spine first and may progress upward. In some cases, the joints where your ribs attach to your spine can also become affected, which may make it harder to take deep breaths.^[1]^[5]

Research shows that about 20 to 30 percent of patients with axSpA develop structural changes visible on X-rays within the first two years of disease. This highlights the importance of early diagnosis and treatment to potentially slow this progression.^[7] Long-term suppression of inflammation through proper treatment may help retard radiographic progression, though more research is needed to fully understand this relationship.^[10]

The progression of axSpA is not the same for everyone. Some people experience mild symptoms that remain stable for years, while others have more severe disease with periods of increased symptoms called flares. Factors that appear to influence disease progression include the level of inflammation visible on imaging tests, whether inflammatory markers in the blood are elevated, and whether you smoke. Men with radiographic axial spondyloarthritis tend to have more visible structural progression than women, though both genders can experience significant symptoms.^[2]^[7]

The difference between radiographic and non-radiographic axial spondyloarthritis is important for prognosis. People with non-radiographic axSpA generally have less visible inflammation on imaging studies and fewer structural changes over time compared to those with ankylosing spondylitis. However, this doesn’t mean nr-axSpA is necessarily milder in terms of symptoms—many people with nr-axSpA experience significant pain and functional limitations. Not everyone with nr-axSpA will progress to develop visible bone changes; some may remain in the non-radiographic category indefinitely.^[7]^[8]

Beyond the spine, axSpA can affect other parts of your body, which influences overall prognosis. Eye inflammation (uveitis) occurs in some patients and requires prompt treatment to prevent vision problems. Inflammatory bowel disease and psoriasis, when present, add complexity to management. Though uncommon, inflammation can affect the heart, particularly the aorta (the body’s largest artery), and people with axSpA have an increased risk for heart attack and stroke compared to the general population. Lung complications are rare but can occur if the rib cage becomes very stiff.^[2]

Smoking appears to have a particularly negative impact on prognosis. In people with axSpA, smoking is associated with earlier onset of back pain, higher disease activity with more pain and stiffness, increased spinal inflammation, greater structural joint damage, and poorer quality of life. Quitting smoking is one of the most important steps you can take to improve your prognosis.^[18]

Regular physical activity and exercise are essential for maintaining a good prognosis. People with axSpA who stay physically active tend to preserve better spinal flexibility and function compared to those who are sedentary. Exercise helps maintain mobility and reduces pain, contributing to better long-term outcomes.^[3]

Survival rate

Axial spondyloarthritis itself is not typically life-threatening, and people with the condition generally have a normal lifespan when they receive appropriate medical care.^[3] The disease primarily affects quality of life through pain, stiffness, and functional limitations rather than directly shortening life expectancy.

However, it’s important to be aware that untreated or poorly controlled axSpA can lead to complications that may affect overall health. Severe spinal fusion combined with osteoporosis (weakening of the bones) can increase the risk of spinal fractures, which are serious injuries. Inflammation affecting the heart or lungs, though rare, can potentially lead to complications that require careful monitoring and management.^[1]^[2]

The increased risk of cardiovascular events, such as heart attack and stroke, in people with axSpA means that attention to heart health is important. Managing inflammation through appropriate treatment, along with addressing traditional cardiovascular risk factors like high blood pressure, high cholesterol, and smoking, helps reduce this risk.^[2]

With modern treatment options including biologic medications that target specific inflammatory pathways, along with physical therapy and lifestyle measures, the vast majority of people with axial spondyloarthritis can expect to live a full life. The key is working closely with your rheumatologist to find the right treatment plan, staying active, and addressing the condition proactively rather than waiting for complications to develop.^[3]