C-Reactive Protein (CRP)

Overview

C-reactive protein (CRP) measures an acute-phase protein produced by the liver in response to inflammation, infection, or tissue injury. It binds to phosphocholine on damaged cells and microbes, activating complement and promoting phagocytosis. Elevated levels indicate acute or chronic inflammation, infection, cardiovascular disease risk, or autoimmune conditions, while low levels suggest absence of significant inflammation. CRP is clinically useful for detecting and monitoring inflammatory processes and assessing cardiovascular risk in hsCRP assays.[pmc.ncbi.nlm.nih]​

Clinical Use Cases

  • Diagnosing and monitoring bacterial infections versus viral.
  • Assessing disease activity in rheumatoid arthritis or inflammatory bowel disease.
  • Risk stratification for cardiovascular events (hsCRP).
  • Evaluating postoperative inflammation or tissue injury.

Specimen Types

  • Serum.
  • Plasma (EDTA, heparin, citrate).
  • Whole blood (point-of-care).

Measurement Methods

  • Immunoturbidimetric assay.
  • High-sensitivity ELISA (hsCRP).
  • Nephelometry.
  • Point-of-care latex-enhanced immunoturbidimetry.

Test Preparation and Influencing Factors

  • No fasting required.
  • Estrogen therapy, pregnancy, or obesity elevate levels.
  • Statins, aspirin, or NSAIDs may lower levels.
  • Serial measurements preferred over single values due to diurnal variation.

Synonyms

  • CRP.
  • High-sensitivity CRP (hsCRP).
  • Ultra-sensitive CRP (usCRP).

Further Reading

  • C-Reactive Protein (CRP) Test; MedlinePlus;