What is the clinical utility of C-Reactive Protein (CRP)?

From the Guidelines

C-Reactive Protein (CRP) has clinical utility as an independent predictor of increased coronary risk.

Clinical Utility of CRP

The clinical utility of CRP is based on its ability to predict coronary risk, with high-sensitivity CRP (hs-CRP) being the most useful marker 1.

• Measurement of hs-CRP: should be performed in a metabolically stable person without obvious inflammatory or infectious conditions, with results expressed as mg/L only, and two assays averaged, fasting or nonfasting, and optimally 2 weeks apart 1.
• Risk assessment: should be modeled after the lipids approach via 3 risk categories: low risk (<1.0 mg/L), average risk (1.0 to 3.0 mg/L), and high risk (>3.0 mg/L) 1.
• Clinical use: hs-CRP may be used at the discretion of the physician in patients judged by global risk assessment to be at intermediate risk (10% to 20% risk of coronary heart disease per 10 years) for cardiovascular disease (CVD) 1.

Limitations and Future Research

While CRP has clinical utility, its use is not without limitations, and further research is needed to determine its effectiveness in guiding treatment and improving outcomes 1.

• Randomized trials: are needed to provide evidence on the outcomes associated with the use of hs-CRP to guide the short- and long-term management of patients 1.
• Cost-effectiveness analyses: are needed to assess additional costs or cost savings through the use of hs-CRP testing 1.

From the Research

Clinical Utility of C-Reactive Protein (CRP)

The clinical utility of C-Reactive Protein (CRP) can be understood through its role in the systemic response to inflammation and its application in clinical medicine. Some key points about the clinical utility of CRP include:

• CRP is a pattern recognition molecule that binds to specific molecular configurations exposed during cell death or found on the surfaces of pathogens, contributing to host defense and the innate immune response 2.
• CRP plasma or serum levels are routinely monitored in inpatients to gauge the severity of their initial illness and injury and their subsequent response to therapy and return to health 3.
• The measurement of CRP has been recommended by the Centers for Disease Control and the American Heart Association for patients at intermediate risk of coronary heart disease, as an association between minor CRP elevation and future major cardiovascular events has been recognized 2.
• CRP has limited utility in the emergency department, but it may be a useful adjunct to serial examinations in equivocal presentations of appendicitis, and it may be elevated with complications or treatment failures in patients with pneumonia, pancreatitis, pelvic inflammatory disease (PID), and urinary tract infections 4.
• CRP directly mediates inflammatory reactions and the innate immune response in the context of localized tissue injury, and its pro-inflammatory isoforms can trigger complement activation, activate platelets, monocytes, and endothelial cells 5.
• CRP acts through Fcgamma receptors to reduce inflammation and protect from certain autoimmune diseases, and its regulatory role in inflammation and autoimmunity has led to an increased appreciation of its host defense functions 6.

Applications of CRP Measurement

Some of the applications of CRP measurement include:

• Screening for inflammation and infectious or inflammatory conditions 4.
• Monitoring the severity of illness and injury and the response to therapy 3.
• Risk stratification of cardiovascular events 2.
• Diagnosing and monitoring diseases such as appendicitis, pneumonia, pancreatitis, pelvic inflammatory disease (PID), and urinary tract infections 4.
• Investigating the role of CRP in autoimmune diseases and developing novel therapeutics for inflammatory diseases 5, 6.