Which laboratory markers rise with infection or inflammation?

• A. ESR and CRP
• B. Hematocrit and platelets
• C. RBC count and hemoglobin
• D. Serum calcium and phosphate

Answer: (A)

Inflammation triggers the liver to release acute-phase proteins, which show up as elevated lab markers. The strongest pair here are ESR and CRP.

ESR (erythrocyte sedimentation rate) rises because inflammation increases proteins like fibrinogen that cause red blood cells to stick together and settle faster in a tube. It’s a sensitive indicator of inflammatory activity, but it’s non-specific and can be influenced by factors such as age, sex, and anemia.

CRP (C-reactive protein) is produced in the liver in response to cytokines (notably IL-6) during inflammation. It rises very quickly, often within hours, and can reach high levels, making it a more immediate and responsive marker of inflammation or infection.

The other options don’t track inflammation as directly: hematocrit and platelets can change with inflammation (platelets may rise, a phenomenon called reactive thrombocytosis), but hematocrit is not a reliable inflammatory marker and isn’t typically used to signal infection. RBC count and hemoglobin usually don’t rise with inflammation and can even fall in chronic inflammatory states. Serum calcium and phosphate are not inflammatory markers.