C reactive protein (CRP) is a biomarker associated with OA. Which option describes an OA biomarker?

• A. C reactive protein (CRP)
• B. Erythrocyte sedimentation rate
• C. Rheumatoid factor
• D. Antinuclear antibodies

Answer: (A)

C reactive protein rises in response to inflammation, and in osteoarthritis it can reflect joint inflammation or activity, making it the best-fit biomarker among the options. It helps indicate ongoing inflammatory processes within the joint and can be useful for monitoring response to treatment. Erythrocyte sedimentation rate is a general, non-specific marker of inflammation and is less specifically tied to OA activity. Rheumatoid factor and antinuclear antibodies are indicators of autoimmune diseases like rheumatoid arthritis and various connective-tissue disorders, not OA.