From the Guidelines
Elevated C-Reactive Protein (CRP) levels are a significant indicator of inflammation in the body, and further evaluation is necessary to determine the underlying cause, which can include infections, autoimmune disorders, inflammatory bowel disease, cardiovascular disease, and tissue injury. When CRP levels are elevated, management depends on identifying and treating the specific cause rather than treating the CRP elevation itself 1. Common causes of elevated CRP include:
- Infections (bacterial, viral, fungal)
- Autoimmune disorders (rheumatoid arthritis, lupus)
- Inflammatory bowel disease
- Cardiovascular disease
- Tissue injury
CRP is produced by the liver in response to inflammatory cytokines, particularly interleukin-6, and serves as an acute phase reactant that helps activate the complement system and enhance phagocytosis 1. Normal CRP levels are generally below 10 mg/L, with levels above this suggesting inflammation, and values exceeding 100 mg/L often indicating serious infection or inflammation.
Key Points to Consider
- Serial CRP measurements can be useful for monitoring response to treatment and disease progression 1
- Elevated CRP predicts all-cause and cardiovascular mortality in both HD and PD patients 1
- CRP may be a stronger predictor of cardiovascular events than the LDL-cholesterol level 1
- A persistent inflammatory response may mediate malnutrition and progressive atherosclerotic CVD by a number of pathogenic mechanisms 1
Recommendations for Clinical Practice
- To obtain a CRP concentration in metabolically stable patients, 2 measurements, fasting or nonfasting, should be made (optimally 2 weeks apart) and the results averaged 1
- If the CRP level is 10 mg/L, then the test should be repeated and the patient examined for sources of infection or inflammation 1
- Risk assessment should be modeled after the lipids approach via 3 risk categories: low risk, average risk, and high risk, with CRP levels of 1.0 mg/L, 1.0 to 3.0 mg/L, and 3.0 mg/L, respectively 1
From the Research
Significance of Elevated C-Reactive Protein (CRP)
Elevated C-Reactive Protein (CRP) levels have been implicated in various diseases and conditions, including:
- Cardiovascular disease: Elevated CRP levels have been associated with an increased risk of cardiovascular disease and may serve as an early marker of the magnitude of inflammation in events such as myocardial infarction 2.
- Infections: CRP is generally highly elevated in invasive bacterial infections and can be used as a marker of inflammation, although a single CRP level is neither sensitive nor specific enough to identify all cases of serious bacterial infection 3.
- Cancer: Elevations in CRP level have been implicated as a useful marker to identify patients at risk for certain cancers 4.
- Autoimmune diseases: CRP has been found to be a significant partaker and prognostic factor in a wide range of autoimmune diseases 5.
- COVID-19: Elevated serum levels of CRP have been associated with severe disease, venous thrombo-embolism, acute kidney injury, critical illness, and in-hospital mortality in patients with COVID-19 6.
Clinical Implications
The clinical implications of elevated CRP levels include:
- Guiding therapy: CRP levels can be used to guide therapy in a context-dependent manner, particularly in patients with cardiovascular disease or infections 4, 3.
- Monitoring disease severity: CRP levels can be used to monitor disease severity and predict disease progression and outcome 4, 2.
- Identifying patients at risk: Elevated CRP levels can be used to identify patients at risk for certain diseases, such as cardiovascular disease or cancer 4, 2.
- Prognostic factor: CRP is a significant prognostic factor in a wide range of diseases, including cardiovascular, autoimmune, and chronic diseases 5.