A nurse is caring for an older adult with rheumatoid arthritis who is taking aspirin 650 mg every 4 hours. Which diagnostic test should be monitored to evaluate the effectiveness of this medication?

• A. WBC count
• B. Rheumatoid factor
• C. Antinuclear antibody
• D. Erythrocyte sedimentation rate

Answer: (D)

The main idea is using a marker of inflammation to track how active the rheumatoid process is over time. Erythrocyte sedimentation rate rises when inflammation is active and falls as inflammation improves. Since aspirin is given to reduce inflammatory activity in RA, watching the ESR helps judge whether the medication is effectively dampening the inflammatory response. The other tests serve different purposes: rheumatoid factor and antinuclear antibodies are helpful for diagnosis but do not reliably reflect current disease activity or response to therapy; a white blood cell count is mainly used to screen for infection or cytotoxic effects, not to measure inflammatory burden in RA. Remember that ESR is influenced by factors like age and anemia, so looking at trends over time is more informative than a single value.