When radiographs are inconclusive, which combination of tests best supports the diagnosis of Ankylosing Spondylitis?

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Multiple Choice

When radiographs are inconclusive, which combination of tests best supports the diagnosis of Ankylosing Spondylitis?

When imaging doesn’t show clear joint damage, you rely on markers that reflect both genetic susceptibility and current inflammation. In ankylosing spondylitis, having HLA-B27 positivity plus an elevated CRP fits this pattern. HLA-B27 is a genetic marker found more often in people with AS, which raises suspicion in the right clinical setting, though it isn’t by itself diagnostic. An elevated CRP indicates active inflammation in the spine and sacroiliac joints, which is characteristic of inflammatory back pain and often appears even when radiographs look normal early in the disease. Together, these two findings strengthen the likelihood of AS and guide clinicians toward further evaluation, such as MRI, to detect active inflammatory changes that radiographs might miss. The other options don’t align with the typical AS workup. RF and ANA are more associated with rheumatoid arthritis or other autoimmune connective tissue diseases. Calcium and phosphate levels don’t indicate inflammatory spine disease. VDRL and HIV testing are aimed at infectious or systemic conditions, not inflammatory back pain disorders.

When imaging doesn’t show clear joint damage, you rely on markers that reflect both genetic susceptibility and current inflammation. In ankylosing spondylitis, having HLA-B27 positivity plus an elevated CRP fits this pattern. HLA-B27 is a genetic marker found more often in people with AS, which raises suspicion in the right clinical setting, though it isn’t by itself diagnostic. An elevated CRP indicates active inflammation in the spine and sacroiliac joints, which is characteristic of inflammatory back pain and often appears even when radiographs look normal early in the disease. Together, these two findings strengthen the likelihood of AS and guide clinicians toward further evaluation, such as MRI, to detect active inflammatory changes that radiographs might miss.

The other options don’t align with the typical AS workup. RF and ANA are more associated with rheumatoid arthritis or other autoimmune connective tissue diseases. Calcium and phosphate levels don’t indicate inflammatory spine disease. VDRL and HIV testing are aimed at infectious or systemic conditions, not inflammatory back pain disorders.

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