From the Guidelines
C-reactive protein (CRP) is a protein produced by the liver that serves as an important inflammatory marker to detect and monitor various inflammatory conditions, infections, and tissue damage. When the body experiences inflammation or infection, CRP levels in the blood rise rapidly, often within hours, making it a valuable diagnostic tool 1. Normal CRP levels are typically below 10 mg/L, with levels above this threshold suggesting the presence of inflammation or infection. Higher levels (over 100 mg/L) generally indicate severe inflammation or bacterial infection. CRP testing is commonly used to assess conditions like rheumatoid arthritis, inflammatory bowel disease, cardiovascular disease risk, and to monitor response to treatment for infections or inflammatory disorders. The test is simple, requiring only a blood sample, and results are usually available quickly, allowing for prompt clinical decision-making. According to the most recent and highest quality study, CRP has the analyte and assay characteristics that are the most conducive for use in practice 1. Some studies have shown that high-sensitivity CRP has consistency across large prospective studies as a risk factor integrating multiple metabolic and low-grade inflammatory factors underlying the development of unstable atherosclerotic plaques 1. However, other studies have raised concerns about the quality of research into prognostic biomarkers, including CRP, and have suggested that the recommendation to use CRP measurements in the management of patients with stable coronary artery disease should be removed from clinical practice guidelines 1. Despite these concerns, CRP remains a valuable tool for detecting and monitoring inflammation in the body. It is essential to interpret CRP results in the context of other clinical factors and to use them in conjunction with other diagnostic tools to ensure accurate diagnosis and effective treatment. In clinical practice, CRP levels should be expressed only as milligrams per liter and expressed to 1 decimal point, and risk assessment should be modeled after the lipids approach via 3 risk categories: low risk, average risk, and high risk 1.
From the Research
Definition and Function of C-Reactive Protein
- C-reactive protein (CRP) is a sensitive biomarker of inflammation 2, 3, 4, 5, 6
- CRP is a plasma protein of hepatic origin, belonging to the pentraxin family, and forms a major component of any inflammatory reaction 4
- It functions as an important modulator of host defense against bacterial infection, tissue injury, and autoimmunity 2
- CRP exists in conformationally distinct forms, which exhibit distinct functional properties and help explain the diverse, often contradictory effects attributed to CRP 2
Role of CRP in Disease
- Elevations in CRP level have been implicated as a useful marker to identify patients at risk for cardiovascular disease and certain cancers 2
- CRP is a marker of atherosclerotic disease and may play a role in its induction 3
- CRP has an anti-inflammatory role in autoimmune diseases, such as systemic lupus erythematosus 3
- CRP is associated with various diseases, including cardiovascular, respiratory, hepatobiliary, gastrointestinal, pancreatic, renal, gynecological, andrological, dental, oral, otorhinolaryngological, ophthalmological, dermatological, musculoskeletal, neurological, mental, splenic, thyroid conditions, as well as infections, autoimmune-supposed conditions, and neoplasms 6
Measurement and Clinical Significance of CRP
- The measurement of CRP is widely used to monitor various inflammatory states 5
- CRP binds to damaged tissue, to nuclear antigens, and to certain pathogenic organisms in a calcium-dependent manner 5
- Interaction of CRP with Fc receptors leads to the generation of proinflammatory cytokines that enhance the inflammatory response 5
- A novel diagnostic algorithm to carefully assess the CRP level for a precise diagnosis of a medical condition is illustrated 6