What diagnostic test is recommended for a patient suspected of having ankylosing spondylosis?

Ankylosing spondylitis is a type of inflammatory arthritis that primarily affects the spine and the sacroiliac joints. The diagnosis of ankylosing spondylitis typically involves a combination of clinical evaluation, imaging studies, and laboratory tests. Among the imaging modalities, spinal x-rays are an essential first-line diagnostic tool for detecting changes associated with ankylosing spondylitis.

Spinal x-rays are particularly useful for identifying characteristic findings such as sacroiliitis, which is inflammation of the sacroiliac joints and is often one of the earliest signs of the disease. Changes in the vertebrae, such as syndesmophyte formation and vertebral fusion, may also become apparent over time, highlighting the progressive nature of the disease.

While blood tests for HLA-B27 can support the diagnosis, as a significant percentage of patients with ankylosing spondylitis are positive for this antigen, the presence of HLA-B27 is not specific enough to confirm the diagnosis on its own. MRI of the spine can provide detailed images and help identify early inflammatory changes that may not be visible on x-rays, but it is typically reserved for cases where the diagnosis is uncertain or when assessing progression. A CT scan of