Ankylosing Spondylitis is difficult to diagnose because it is hard to distinguish it from other conditions such as psoriatic arthris and reactive arthritis. The Arthritis Research Campaign site says that "AS is often not diagnosed until a patient has had backache for two or three years or even longer".
Inflammatory back pain together with a history of iritis, psoriasis,inflammatory bowel disease or recent infection is considered to be a good indicator.
Early diagnosis is considered important because the correct early treatment stands the best chance of minimising the damage that AS does.
Physical examination
A physical examination is normally undertaken to look for any stiffening in the spine and neck and any inflammation of the eye. The sacroillac joints in the upper buttocks should also be checked for any tenderness. Other joints should also be examined so as to exclude other inflammatory conditions.
Imaging
X-rays may not show anything wrong in the early stages of AS even though the pain and stiffening can be quite severe. Inflamed joints between the spine and pelvis may initially show up as blurred and indistinct. Multiple Resonance Imaging (MRI) is considered to be the most effective tool in identifying inflammation of the sacroillac joints and may be considered for those who have inflammatory back pain and have tested positive for HLA-B27 but who have "normal" x-ray results.
Blood and Urine Tests
Tests for elevated levels of C reactive protein and eryrthrocyte sedimentation rates may indicate the presence of AS. Some people with AS may have normal results for these tests. The presence of the HLA-B27 gene is also an indicator that AS may be present although this again is not conclusive.
Urine tests may be taken to look for accompanying kidney abnormalites and to exclude kidney conditions that may produce back pain.
