Spotting Spondylitis

Ankylosing spondylitis diagnosis is a complex process

/ Author:  / Reviewed by: Chris Galloway, M.D.

So you've had back pain for awhile now, and it's not going away. Maybe your pain is especially bad when you wake up in the morning. While there are many causes of back pain, ankylosing spondylitis could be to blame in your case.

But don't jump the gun, as ankylosing spondylitis (AS) isn't all that common. Before you accept that you have AS, you should see a doctor or rheumatologist for a proper diagnosis.

As an expert in inflammatory joint diseases like AS, a rheumatologist can assess your symptoms and run the necessary tests to see if your back pain is the result of AS.

Even though there is no one test to clearly diagnose AS, a rheumatologist can put together the various pieces of the puzzle to determine if you're living with this chronic condition.

Symptoms of AS

If you think you have AS, your first step should be to see your doctor and explain your symptoms. So, what are the symptoms of AS?

The early signs and symptoms of AS are typically pain and stiffness in the lower back and hips. These symptoms are often worse at night, in the morning or when you've been inactive.

At first, the symptoms may be so subtle that you don't even notice them. But over time, they can become worse. You may even notice that symptoms improve or stop altogether. However, that does not mean the disease is gone.

The areas of the body most commonly affected by AS include:

  • The sacroiliac joint, or joint between the spine and pelvis
  • The vertebrae (bones that make up the spinal column) in the lower back
  • The points at which tendons and ligaments connect to bones, mainly in the spine
  • The cartilage between the breastbone and ribs
  • The joints of the hip and shoulder

Back pain often starts in the sacroiliac joints. Though eventually, pain may run through all of the spine.

AS can lead to loss of motion in the lower spine or the inability to fully expand the chest because of joint involvement between the ribs. Fatigue is another common symptom.

Other less common symptoms of AS include:

  • Uveitis (swelling of the middle layer of the eye called the urea)
  • Heel pain
  • Pain and swelling in the joints of the knees and ankles
  • Appetite loss
  • Slight fever
  • Weight loss

If you have long-standing pain and stiffness in your lower back and hips, or trouble taking deep breaths because of chest pain, it is probably time to see a doctor for AS diagnostic testing.

Diagnosing AS

A typical diagnosis of AS involves a physical examination, imaging tests and blood tests.

Physical Examination

When making an AS diagnosis, your doctor takes into a account several important factors, including:

  • AS symptoms usually start before 35 years of age.
  • Pain is chronic; that is, it has lasted for more than three months.
  • Back pain and stiffness get worse with inactivity, especially at night or in the early morning.
  • Physical activity and exercise tend to reduce back pain and stiffness.
  • Symptoms are eased with use of nonsteroidal anti-inflammatory drugs (NSAIDs), which include over-the-counter medications such as ibuprofen (Advil, Motrin) and aspirin (Bayer, Excedrin) or other prescription medications.

During a physical exam, your doctor will look for sites of inflammation by assessing pain and tenderness in your back, pelvis, hips, sacroiliac joints, chest and heels. Your doctor is also likely to evaluate your flexibility and spinal mobility.

In addition, your doctor will likely look for other signs and symptoms of AS, including a history of eye inflammation and gastrointestinal infections, a family history of AS and fatigue that results from inflammation.

Imaging Tests

One of the defining characteristics of AS is joint inflammation, particularly of the sacroiliac joint. Doctors use imaging tests to spot the erosion or damage caused by inflammation.

The two main imaging tests used in AS diagnosis are x-rays and magnetic resonance imaging (MRI).

X-rays are supposed to show erosion. However, not every patient with AS has developed visible signs of joint damage. In many cases, it can take up to seven to 10 years for serious damage to show up in x-ray images.

MRI is another imaging tool used to spot joint involvement. Yet, doctors and researchers still aren't certain how to properly interpret MRI results for an AS diagnosis. Furthermore, MRIs can be very expensive.

Blood Tests

Blood testing is used to look for markers of inflammation. If your joints are inflamed, your body may release extra protein from those joints into the bloodstream. 

Common tests used to detect this increase in protein include:

  • Erythrocyte sedimentation rate (ESR)
  • C-reactive protein (CRP)
  • Plasma viscosity (PV)

The results of these tests are not foolproof indicators of AS. According to the UK's National Ankylosing Spondylitis Society, "[W]e know that in around 30 to 40 percent of cases of AS, inflammatory markers will be within the normal range. Therefore, just because your inflammatory markers are normal, it does not mean you do not have a form of inflammatory arthritis [such as AS]."

The Spondylitis Association of American notes, "Since there is no single blood test for AS, laboratory work may not be of much help. A simple ESR is commonly an indicator of inflammation. However, less than 70 percent of people with AS have a raised ESR level."

Blood testing may also be used to spot a gene that has been associated with AS. This gene, called HLA-B27, is present in about 8 percent of the Caucasian population. But no more than 2 percent of people born with this gene will go on to develop AS.

Having the HLA-B27 gene does not necessarily mean you have AS. Similarly, testing negative for the gene does not mean you don't have AS. However, testing positive for the gene may offer clues about your symptoms.

No Easy Task

Neither diagnosing nor living with AS is an easy task. But the only path towards pain relief and improved mobility is to work closely with your doctor and rheumatologist to get a proper diagnosis and treatment.

Review Date: 
March 22, 2013