Allied Health Care Professionals: A Critical Link for Detection of Ankylosing Spondylitis

This report is based on medical evidence presented at sanctioned medical congress, from peer reviewed literature or opinion provided by a qualified healthcare practitioner. The consumption of the information contained within this report is intended for qualified Canadian healthcare practitioners only.


October 2008

<div style="border: 1px solid #808080; background: #f0f0f0; padding: 5px; padding-top: 0;">

<img src="/image/tools_pdf_mini.gif" alt="" style="vertical-align: middle;"> [PDF->/pdf/HO09-002_Inman.pdf?id_mot=25]<br /><img src="/image/tools_pdf_mini.gif" alt="" style="vertical-align: middle;"> [Download the Questionnaire - PDF->/pdf/HO09-002_Questionnaire.pdf?id_mot=25]<br /><img src="/image/tools_pwp_mini.gif" alt="" style="vertical-align: middle;"> [Slides->/ppt_HO09-002_web.ppt?id_mot=25]

If you would prefer to receive a CD-Rom of this slide kit, please use the “[Contact Us->/index.php?page=contactus&lang=en]” icon above.


Editorial Overview:

Robert D. Inman, MD, FACP, FRCPC

Director, Spondylitis Program, Toronto Western Hospital, Professor of Medicine, University of Toronto, Toronto, Ontario

Low back pain is an important public health problem in all industrialized countries (Loney PL, Stratford PW. Phys Ther 1999;79:384-94) and it appears to occur far more commonly among both physiotherapists and chiropractors. One survey of 311 physiotherapists in Edmonton, Alberta, for example, found that almost 50% reported back pain due to work—a significantly higher prevalence than reports of work-related back pain in 27% of the general population (Mierzejewski M, Kumar S. Disabil Rehabil 1997;19:309-17).

The overall prevalence of back pain as recorded by a sample of 320 Canadian chiropractors was reportedly 87%, of which 74% was for low back pain (Mior SA, Diakow PR. J Manipulative Physiol Ther 1987;10:305-9). With these high prevalence rates, it is clear that both physiotherapists and chiropractors are frequently assessing low back pain and are thus well positioned to seek out the estimated 5% of patients who present with low back pain in general practice who actually have early symptoms of ankylosing spondylitis (AS).

Disease Prevalence

Although the rate of AS is low, it is one of the most debilitating rheumatic disorders. When radiographic sacroiliitis is visible, the diagnosis is usually clear. Abnormalities on magnetic resonance imaging (MRI) may appear before X-ray changes in the sacroiliac joints. As the disease progresses, radiographic spinal changes such as syndesmophytes and facet joint obliteration can be seen, indicating the severity and chronicity of the disease with very limited mobility.

Currently, between 150,000 and 300,000 individuals in Canada are affected by AS. It is most common in European Caucasians (prevalence of 0.2% to 1.2%), and the typical age of onset is between 15 and 30 years—onset after 40 is uncommon but can be seen. Men are also three times more likely to be afflicted with AS than women and it does tend to run in families, suggesting heritable factors drive AS. Indeed, 80% to 95% of affected patients have the human leukocyte antigen (HLA)-B27 gene, which is otherwise present in only 7% of the general Caucasian population. Importantly, however, only a minority of individuals who carry this antigen develop AS, suggesting that other triggers, possibly environmental, contribute to the development of AS in susceptible individuals.

Table 1.

Typical Patient Profile

With this brief background, below is an example of the type of patient a physician might seek to investigate more closely for possible AS.

A young Caucasian male, under the age of 30, presents with complaints of low back pain and stiffness that has been bothering him for over three months. He casually mentions that it is probably arthritis, as his mother suffers from longstanding arthritis, and his own hip is acting up, as well, making him think he probably has arthritis himself. Upon examination, he has scaly patches on his legs and arms—possibly a type of psoriasis. When you inquire whether his symptoms respond well to any of the NSAIDs such as ASA or ibuprofen, he confirms that they do, often quite dramatically.

Further Symptoms

One of the clues indicating AS and not simply degenerative back pain is low back pain of insidious onset that cannot be linked to any specific action. Sacroiliitis or inflammation of the joint linking the lower spine to the pelvis may also be present, along with heel pain or enthesitis. Arthritis especially in the shoulders and hips can be present as well, even at earlier stages of the disease. Less commonly, toes or fingers may be diffusely swollen—often referred to as sausage digits or dactylitis. Again less commonly, patients can develop iritis or uveitis, symptoms of which include sensitivity to light, red eye, blurred vision, tearing and pain. Inflammatory bowel disease and psoriasis can also accompany AS, each occurring in about 10% of AS patients.

Simplifying Diagnosis: The Likelihood Criteria

These clinical parameters do increase the likelihood of the disease being present, but may be absent in earlier stages of the disease, so the absence of accompanying symptoms does not rule out early AS.

As described by Rudwaleit et al. (Arthritis Rheum 2006;54:569-78), acute back pain is often nonspecific in nature and in approximately 90% of patients, it subsides without intervention within three months. Conversely, back pain in AS is inflammatory in nature and is expressed in key clinical symptoms. With this in mind, investigators focused on a group of patients under 50 years of age who presented with chronic back pain, 101 of whom had AS and 112 of whom had mechanical low back pain. They sought to determine the most relevant set of symptoms that occur significantly more often in AS patients.

Some 96% of the AS patients reported onset of back pain at less than 40 years of age and 84% at less than 30 years of age. Very acute onset (within one hour) was reported significantly less often by AS patients than those with mechanical low back pain, consistent with the insidious nature of symptom onset that characterizes AS.

Over two-thirds of those in the AS group also reported morning stiffness lasting more than 30 minutes compared to about 25% of controls. The majority of AS patients indicated that their back pain improved with exercise, compared to only about half of those in the control group, significantly more of whom indicated their back pain improved with rest. As well, more than one-third of AS patients experienced an alternating type of buttock pain vs. about 11% of controls, and more AS patients reported that they woke up in the very early morning hours than controls.

The authors concluded that their new set of criteria based on four parameters in inflammatory back pain provided the best feasibility and balance between sensitivity and specificity for application as a diagnostic tool in daily practice in patients with established disease. In applying the parameters as classification criteria, they calculated that best tradeoff between sensitivity and specificity was if patients fulfilled two out of the four parameters, where the positive likelihood ratio of a patient having AS was 3.7 with a sensitivity and specificity of 70.3% and 81.2%, respectively. As diagnostic criteria, if patients met three out of the four parameters, the positive likelihood ratio increased to 12.4. Thus, questioning patients on the four key criteria can help in the diagnosis of AS (See questionnaire).

Spinal Mobility Measures

Adding to patient history and the four basic questions (top section of questionnaire on page 4) mentioned above, mobility tests add weight to suspicion of AS. In the same study by Rudwaleit et al., investigators assessed both anterior and lateral spinal flexion in both groups of patients. Using Schöber’s test, they discovered a restriction in anterior spinal flexion of <5 cm in 90.7% of AS patients but in only 35% of patients with mechanical low back pain.

Lateral spinal flexion was similarly restricted to <10 cm in significantly more AS patients at about 34% compared to only about 5% of those without. As confirmed in their own study, the authors emphasized that spinal mobility is frequently restricted in established and longstanding AS. The test for lateral spinal flexion was far more specific for AS in their particular cohort (mean duration of back pain of 12.9 years) than the test for anterior spinal flexion, a finding which is not consistent with other reports.

It is important to note that while limited spinal mobility is a cardinal sign of AS, the diagnostic value of spinal mobility tests remains unknown in early disease.


For early diagnosis of AS, X-rays are not helpful. According to Rudwaleit et al. (Arthritis Rheum 2005;52(4):1000–8), it takes years from onset of inflammatory back pain to appearance of radiographic sacroiliitis. In his study, after five years, radiographic evidence of sacroiliitis was observed in 36% of patients, up to 59% after 10 years, which corresponds to the general variable time to AS diagnosis of eight to 11 years.

MRI can detect sacroiliitis earlier. At this point in time, use of MRI remains challenging, as it is not widely available, nor easily accessible throughout Canada. But a high degree of AS likelihood should be a justification for MRI study if the pelvis X-ray is nondiagnostic.

However, when AS is suspected in a patient with chronic back pain with inflammatory features, laboratory testing for HLA-B27 is useful and increases diagnostic likelihood of AS if inflammatory back symptoms are present.


AS is a chronic inflammatory disease that leads to stiffening, erosion and fusion of the spine. Although it is a heterogenous disease difficult to identify, simple diagnostic tools have been developed and refined to help in diagnosing AS earlier. In the era of effective new treatments for AS, there should be an emphasis on early detection and early referral. While the ultimate goal would be a cure, diagnosing earlier is the main challenge to slow disease progression and maintain patient activity and freedom of movement longer. As studies with therapies such as the biologic infliximab have shown to offer the possibility of preventing further structural damage, physiotherapists and chiropractors are key players in identifying the individual who would benefit from early
ologist (Figure 1).


We Appreciate Your Feedback
Please take 30 seconds to help us better understand your educational needs.
Are you a healthcare professional practicing in Canada?
What type of healthcare professional best describes you?
Did you find this publication to be of educational value?
What is you preferred format for receiving and reading a report?
Would you like to have video available with the report?
Suggested future topics: