Tests to Diagnose Axial Spondyloarthritis

Diagnosing AxSpA spectrum conditions can be challenging. A variety of symptoms may be present, with or without visible changes on imaging tests. It’s important to have a thorough diagnostic process that includes a variety of things, including a medical history, physical examination, and if need be, various tests.

Tests can be helpful in confirming a diagnosis or providing more information about a condition. It is possible to have inconclusive results from tests and still be diagnosed with an AxSpA spectrum condition based on a medical history and physical examination. While tests can provide more information, they are not the only thing a diagnosis should be based upon.

Two commonly used kinds of tests in the diagnostic process of AxSpA spectrum conditions are blood tests and imaging tests.

Blood tests

There are no blood tests that can exclusively confirm or exclude AxSpA spectrum conditions.1 There is a specific human leukocyte antigen (HLA) gene, HLA-B27, that is strongly associated with AxSpA spectrum conditions.1,2 The HLA-B27 gene is present in over 90 percent of people with AxSpA conditions.3 Having this gene does not necessarily mean you will definitely develop an AxSpA condition, but it does increase your risk. This also means that you can still have an AxSpA condition even if you do not have the HLA-B27 gene – a negative test does not necessarily rule that diagnosis out.

Other markers that blood tests might be measuring are inflammation markers. When inflammation occurs in the body, extra protein can be released and then float through the blood.3 Blood tests that might be done for other inflammation markers can include tests for erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and plasma viscosity (PV).3 Again, though, normal blood tests aren’t enough to rule out AxSpA spectrum conditions. Approximately half of all AxSpA spectrum diagnoses will also have normal blood test results.3

Imaging tests

Imaging tests are often utilized in diagnosing AxSpA spectrum conditions, although like blood tests, they should not be the only diagnostic tool or criteria. X-rays, magnetic resonance imaging (MRI), computed tomography (CT scans), and ultrasound (US) may be used to help diagnose or rule out possible AxSpA spectrum diagnoses.4

These tests can show new bone formation, structural damage, and inflammatory changes to joints in the spine and pelvis. Even with no structural damage or changes, AxSpA spectrum conditions can still be present, so these tests are just part of the diagnostic process.

Imaging tests should be used to complement the diagnostic process, along with individual disease characteristics, presenting symptoms, and individual-specific indications.4 Certain imaging tests are more sensitive than others, especially in earlier stages of the AxSpA spectrum, and taking that into consideration when making a diagnosis can be helpful.

While imaging tests may be used in diagnosis, they can also be used for assessment of disease activity, monitoring structural damage, and aiding in prognosis of the AxSpA spectrum condition.4

Talk with your doctor about any tests they may be ordering in the diagnostic process, and what the results might mean for you. Knowing more about each test and what the results can – and might not – mean can be helpful in starting conversations with health care providers and helping you get an appropriate diagnosis.

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Written by: Jaime Rochelle Herndon | Last reviewed: May 2020