A 22 year old male presents with complaints of dull lower back pain and morning stiffness. The pain was initially episodic, but now has become persistent and bilateral. On physical examination, there is tenderness over the costosternal junctions, spinous processes of the veebrae, and the iliac crests. Which of the following tests would be most likely to be helpful in establishing a diagnosis of ankylosing spondylitis?
A 22 year old male presents with complaints of dull lower back pain and morning stiffness. The pain was initially episodic, but now has become persistent and bilateral. On physical examination, there is tenderness over the costosternal junctions, spinous processes of the veebrae, and the iliac crests. Which of the following tests would be most likely to be helpful in establishing a diagnosis of ankylosing spondylitis?
💡 Explanation
**Core Concept:** Ankylosing spondylitis (AS) is a chronic inflammatory disorder affecting the axial skeleton, primarily involving the sacroiliac joints, sacrum, vertebral columns, and other joints. It often presents with non-radicular lower back pain and morning stiffness, with possible spinal deformity over time. The axial inflammation can lead to hyperkyphosis, or "bamboo spine" deformity.
**Why the Correct Answer is Right:** The correct answer, **D. X-rays (anteroposterior pelvic and spine views)**, is chosen due to their ability to show the characteristic changes in AS. Anteroposterior pelvic views can demonstrate sacroiliitis (inflammation of the sacroiliac joints), while anteroposterior spine views can show spinal deformities like syndesmophytes (bone growths) and paravertebral osteopenia (reduced bone density).
**Why Each Wrong Option is Incorrect:**
A. **Labs (erythrocyte sedimentation rate, C-reactive protein):** While these lab tests are useful for monitoring disease activity and response to treatment, they are not specific for AS diagnosis. Other inflammatory conditions can also cause elevated ESR and CRP.
B. **Imaging (CT, MRI):** While Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) are valuable for diagnosing AS, the correct answer (X-rays) is more readily available, cost-effective, and can show the characteristic changes in AS.
C. **Physical examination:** While physical examination is essential in clinical evaluation, it doesn't specifically diagnose AS. Other rheumatological conditions can cause similar symptoms and signs.
**Clinical Pearl:** Ankylosing spondylitis (AS) is typically diagnosed based on a combination of clinical (symptoms and signs), laboratory, and imaging findings. HLA-B27 gene marker is often tested to confirm the diagnosis, especially if clinical suspicion is high but imaging and labs are inconclusive.
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**Why the Correct Answer is Right:**
D. **X-rays (anteroposterior pelvic and spine views):** X-rays are crucial for diagnosing AS as they demonstrate characteristic changes such as sacroiliitis (inflammation of the sacroiliac joint) and spinal syndesmophytes (bone spurs) on anteroposterior pelvic and spine views, respectively. These changes indicate chronic inflammation and joint fusion, hallmarks of AS.
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**Why Each Wrong Option is Incorrect:**
A. **Labs (erythrocyte sedimentation rate, C-reactive protein):** Although lab tests like ESR (erythrocyte sedimentation rate) and CRP (C-reactive protein) can indicate inflammation, they are not specific to AS and can be elevated in other inflammatory conditions as well.
B. **Imaging (CT, MRI):** Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) are valuable for diagnosing AS, but X-rays are more readily available, cost-effective,
✓ Correct Answer: C. HLA typing
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