Review Question - QID 103001

This patient is a young man with back pain that improves with exertion and has a decreased range of motion which is consistent with ankylosing spondylitis (AS). The most appropriate initial diagnostic test is a radiograph of the sacroiliac joint.

AS is a seronegative spondyloarthropathy that commonly causes chronic inflammatory disease in the spine and sacroiliac joints. Typically, this spondyloarthropathy affects young men. AS involves the spine and sacroiliac joints, hips, shoulders, entheses, and peripheral joints, as well as having extra-articular manifestations (such as uveitis, inflammatory bowel disease, and aortic insufficiency). Radiographic findings include symmetric sacroilitis, ankyloses, and sacroiliac joint fusion. There is a strong correlation between HLA-B27 and AS, and HLA-testing is warranted in an individual with imaging suggestive of AS. Nonsteroidal anti-inflammatory drugs (NSAIDs) can provide substantial relief from inflammatory back pain. NSAIDs are considered first line in the pharmacologic treatment of AS. If patients are unresponsive to NSAIDs, sulfasalazine can then be used. The best initial test in the workup of AS is a radiograph of the sacroiliac joint and the most accurate test is an MRI of the sacroiliac joint.

Incorrect Answers
Answer 1: Erythrocyte sedimentation rate (ESR) is a nonspecific assessment of inflammation. It is positive in many infectious and inflammatory conditions but is nonspecific and would not change further imaging workup.

Answer 2: HLA-B27 testing is not the best initial test. If the patient has a negative radiograph and has some findings suggestive of a spondyloarthropathy, HLA-B27 testing should be pursued. HLA-B27 is seen in PAIR conditions - psoriasis, ankylosing spondylitis, inflammatory bowel disease, and reactive arthritis.

Answer 3: MRI sacroiliac joint is incorrect but may be pursued if radiography is inconclusive. This is the most accurate test in the workup of ankylosing spondylitis.

Answer 5: Slit-lamp examination is incorrect as it would not confirm the diagnosis of AS. It is true that extra-articular manifestations of AS include uveitis which may warrant a slit-lamp exam.

Bullet Summary:
The most appropriate initial step in the workup of ankylosing spondylitis is a radiograph of the sacroiliac joint.