What Are Diagnostic Tests for Axial Spondyloarthritis?

Reviewed by: HU Medical Review Board | Last reviewed: May 2020 | Last updated: January 2021

Diagnosing conditions on the AxSpA spectrum can be difficult, since many of the symptoms can also be symptoms of other conditions. Especially if nothing shows up on imaging tests, doctors may not realize that the symptoms are indicative of certain conditions. An accurate, early diagnosis is important in order for an appropriate treatment plan to be put in place.

Knowing what goes into a diagnosis of conditions on the AxSpA spectrum can help you be empowered to ask your doctor questions about tests and diagnoses. Asking questions and talking with your doctor about your symptoms can help you get the tests you need to get an accurate diagnosis.

Importance of early diagnosis

Delays in diagnosing conditions on the AxSpA spectrum can take as long as 5 to 10 years after the onset of the condition.1 For ankylosing spondylitis (AS), it is estimated that delays in diagnosis can take up to 8-11 years after the onset of symptoms.2 A delay in diagnosis means appropriate treatment is delayed. This means the SpA is progressing without any treatment, causing worsening of symptoms, joint damage, and impaired quality of life.

Diagnosing AxSpA spectrum conditions

Many people see their primary care doctor for symptoms of AxSpA spectrum conditions. These doctors may not always recognize symptoms of AxSpA conditions and misdiagnose them. To diagnose AxSpA spectrum conditions, a medical history is typically taken, including any symptoms that the person may be experiencing, as well as a family history of symptoms.3 A physical exam is done, and differential diagnosis is made.

Back pain due to inflammation is different than general back pain. Back pain from inflammation typically has certain characteristics:3

  • Improves with exercise or movement
  • No improvement with rest or inactivity
  • Pain is worse at night and early morning
  • Morning stiffness
  • Pain alternates between buttocks
  • Pain lasting more than 3 months
  • Having 4 or more of these characteristics generally means the back pain may be caused by inflammation.3

Imaging tests like X-rays may be done. An X-ray may be done of the sacroiliac (SI) joints. Changes of these joints on X-ray indicate SpA.4 If changes do not show up on X-ray but your doctor strongly suspects a condition on the AxSpA spectrum, or if minor changes are visible on X-ray, the doctor may order magnetic resonance imaging (MRI), which can provide better images of these joints and possibly show minor changes to these joints before an X-ray can.4

Even without any changes on imaging tests, an AxSpA spectrum condition may be present, which is why the entire clinical picture should be considered, including all reported symptoms. Having a family or person history of comorbid conditions such as psoriasis, uveitis, ulcerative colitis or Crohn’s disease should raise suspicion that back or joint pain might be due to a spondyloarthropathy.

Other tests that might be ordered include blood tests, namely a blood test for the HLA-B27 gene. This is the major gene that has been associated with SpA and conditions on the AxSpA spectrum.4 Having this gene does not necessarily mean you will definitely develop SpA, but many people with this gene are more likely to have a condition on the AxSpA spectrum than other kinds of arthritis.4 Not all patients may test positive for HLA-B27 and your specialist may look for other gene markers, including the ERAP1, IL1A, and L23R markers. Other tests might include checking levels of inflammation in the blood with a ESR (Sed rate) or CRP level which can be elevated with inflammatory arthritis.

If a diagnosis of an AxSpA spectrum is strongly suspected or diagnosed, a referral to a rheumatologist is generally recommended.3 This is because rheumatologists specialize in conditions like this and can provide a thorough workup and confirmation of the diagnosis and establish a treatment plan.

Active vs stable disease

Upon examination and talking with a person, doctors will determine whether the AxSpA condition is classified as either “active” or “stable.” This classification can change over time and is not fixed. Active disease is disease that causes symptoms that are uncomfortable enough to be labeled unacceptable for the person experiencing them.5 Stable disease is either disease that has no symptoms presently, or symptoms that are uncomfortable but tolerable for the person.5 In order to be classified as stable, this must occur for at least 6 months.5

If you’re having symptoms of AxSpA spectrum conditions, see your doctor. Talk with your doctor about the symptoms you’re experiencing and any family medical history you may be aware of that might be related. Knowing what tests may be ordered and what goes into a diagnosis of AxSpA spectrum conditions can help you make sure you’re getting a complete diagnostic process for your symptoms.

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