A 25-year-old woman is evaluated during a follow-up visit for an 18-month history of ankylosing spondylitis. She has minimal lower back pain with morning stiffness lasting 20 minutes. She is able to pursue her activities of daily living without any restrictions. She has been taking etanercept for 1 year with good results.
On physical examination, vital signs are normal. Full range of motion of the thoracic and cervical spine without tenderness is noted. There is no lumbar or sacroiliac tenderness. The Schober test increases by 5 cm (same as at the time of diagnosis).
Laboratory studies are notable for a normal erythrocyte sedimentation rate and a normal C-reactive protein level.
At the time of diagnosis, radiographs showed normal thoracic and lumbar spine and sacroiliac joints, and an MRI showed edema of the sacroiliac joints and in the lumbar and thoracic spine.
Which of the following should be performed next?
A. Bone scan
B. CT of the sacroiliac joints
C. MRI of the sacroiliac joints
D. Plain radiography of the sacroiliac joints
E. No new imaging
MKSAP Answer and Critique
The correct answer is E. No new imaging.
No new imaging is required for this patient with ankylosing spondylitis. She is currently feeling well, continues to respond well to treatment, and has normal inflammatory markers, making new imaging unnecessary. As with any test, imaging to follow disease activity should be performed only if clearly indicated by the clinical situation (for example, if the result is likely to change management). According to the 2010 Assessment of SpondyloArthritis international Society/European League Against Rheumatism (ASAS/EULAR) guidelines, serial imaging of patients with ankylosing spondylitis can be part of a comprehensive monitoring plan that also includes patient history (such as questionnaires like the Bath Ankylosing Spondylitis Functional Index [BASFI] or Bath Ankylosing Spondylitis Disease Activity Index [BASDAI]), clinical parameters (such as physical examination findings like the Schober test), and laboratory tests (such as erythrocyte sedimentation rate and C-reactive protein). The ASAS/EULAR recommendations state that spinal radiography should not be repeated more frequently than every 2 years unless absolutely necessary in specific cases. The Schober test measures range of motion of the lumbar spine and is an inexpensive and noninvasive physical examination tool for assessing spine involvement and progression; greater than 4 cm is normal.
Bone scan, CT, MRI, and plain radiography may demonstrate evidence of inflammation and/or progression of disease, but without a clear indication may unnecessarily expose the patient to radiation and to expense. This patient is feeling well, has intact activities of daily living, and had radiographs less than 2 years ago; therefore, no additional imaging is necessary at this time.
- Patients with ankylosing spondylitis who are responding well to treatment should be monitored clinically and do not require periodic imaging studies less than every 2 years unless absolutely necessary.
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