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Ankylosing Spondylitis Diagnosis
Ankylosing spondylitis is one of a number of conditions known as seronegative spondyloarthropathies. These are conditions where the mechanism of the pathology is a lesion and resulting inflammation of the connection (enthesis) of tensile tissue into the bone. X-rays may show this inflammation and the spinal changes characteristic of ankylosing spondylitis. Unfortunately, changes that can be picked up from an x-ray usually occur 8-10 years after the onset of ankylosing spondylitis symptoms so are not at all beneficial in catching the disease early and precipitating implementation of preventative treatment strategies.
MRI and CT scans may be able to detect earlier changes in spine health, but are still being investigated as to their benefits in diagnosing the condition. A physical test called Schober’s test can be conducted to measure the flexibility of the lumbar spine. In this test the doctor marks the patient’s fifth lumbar vertebrae and then places a finger on the back five centimetres below this mark and another finger ten centimetres above the mark. The increased distance between these fingers is then measured as the patient bends their back to touch their toes. If the distance increases by less than five centimetres then the patient is considered to have poor flexion of the lumbar spine.
Blood Tests for Ankylosing Spondylosis
Blood tests may detect increased levels of C-reactive protein at times of acute inflammation. Rates of erythrocyte sedimentation also become elevated in some ankylosing spondylitis sufferers, but these blood biomarkers are not universal and so cannot provide a useful diagnostic technique for the condition. Similarly testing a patient with back and neck pain may show them to have the HLA-B27 genotype, but this does not prove conclusively that they have the disease, rather that it is a condition to investigate more thoroughly in establishing a diagnosis and therapeutic plan for ankylosing spondylitis. Other genes involved in the aetiology of ankylosing spondylitis include the ARTS1 and IL23R, as discovered by researchers in 2008 (Bronez, et al). Over 70% of the occurrences of ankylosing spondylitis are estimated to be accounted for by these three genotypes.
Although there are similarities in symptoms to rheumatoid arthritis, there are some significant clinical differences which will affect diagnosis. Rheumatoid arthritis has a higher incidence in women and is often associated with rheumatic fever (85% presence) whereas ankylosing spondylitis is more common in men and usually has no associated fever. Dyspnoea and cough may be present due to the effects of the disease on the lungs. Vision impairment, blurring, floating visual disturbances, and photophobia, with redness and swelling of the eye may be found in ankylosing spondylitis.
BASDAI Diagnostic Tool
A further diagnostic tool is the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) which is used to detect inflammation caused by the disease (Garrett, 1994). Along with the HLA-B27 genotype, x-ray, MRI, and persistent buttock pain relieved by exercise, this test can help establish an ankylosing spondylitis diagnosis. A similar index, the Bath Ankylosing Spondylitis Functional Index (BASFI) assesses the impairment of function experiences by a patient due to the disease, and can be a useful tool to record the improvements, if any, made through therapeutic intervention (Calin, 1994).
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Last Updated: 9/10/2010