Which lab finding is commonly associated with Ankylosing Spondylitis?

• A. Back pain for 3 months
• B. + HLA-B27 (does not always mean AS)
• C. Elevated RF
• D. Increased ESR/CRP

Answer: (D)

Inflammation in the spine drives an increase in acute-phase reactants produced by the liver, so markers like ESR and CRP rise when ankylosing spondylitis is active. These inflammatory markers are commonly elevated and are useful for gauging disease activity and response to treatment, making increased ESR/CRP a typical lab finding in AS.

HLA-B27 is often present in people with AS, but it isn’t universal, so it’s associated rather than definitive. Rheumatoid factor is usually negative in ankylosing spondylitis, reflecting its seronegative nature. A symptom like back pain for several months is important clinically, but it’s not a lab finding.

Thus, the lab finding most commonly linked to AS is increased ESR/CRP.