From the Guidelines
Elevated CRP values are primarily indicative of acute inflammation, infection, or tissue damage, with normal levels typically below 10 mg/L, and values above this threshold suggesting an inflammatory process.
CRP Value Interpretation
The interpretation of CRP values is crucial in clinical practice, as it can help identify patients at risk of various diseases.
- Normal CRP levels are typically below 10 mg/L, with values above this threshold suggesting an inflammatory process 1.
- Higher levels (over 100 mg/L) often indicate serious bacterial infections, while moderate elevations may occur with viral infections, autoimmune disorders like rheumatoid arthritis, or inflammatory bowel disease.
- CRP rises rapidly within 6-8 hours of an inflammatory stimulus and can increase several hundred-fold during acute inflammation.
Clinical Application
CRP is a non-specific marker, meaning it doesn't identify the cause or location of inflammation, so results must be interpreted alongside clinical findings and other diagnostic tests.
- Some physicians also use high-sensitivity CRP (hs-CRP) to assess cardiovascular risk, with levels above 3 mg/L suggesting increased risk of heart disease 1.
- However, recent studies suggest that CRP values >10 mg/L are not always indicative of acute infection/injury, and a more thoughtful approach is needed to interpret these values 1.
Recommendations
A CRP value of 10 mg/L or higher should be interpreted with caution, considering the patient's clinical context and other diagnostic tests.
- Additional steps, such as using a clinical index of the acute phase response/infection or evaluating hepatic health, may be necessary to increase confidence in the interpretation of CRP values 1.
- Researchers may wish to perform statistical Winsorization to preserve the rank position of extreme values in the distribution while lessening skewness 1.
From the Research
CRP Value Indications
- A CRP value of less than 10 mg/l is indicative of a healthy individual 2
- A CRP value of more than 1,000 fold increase is indicative of serious inflammation 2
- A CRP value of ≥500 mg/L is highly related to bacterial infections and is associated with a high one-month mortality rate of 27% 3
- Elevated CRP levels are also associated with an increased risk of cardiovascular disease and certain cancers 4
Clinical Significance of CRP Values
- CRP is a sensitive biomarker of inflammation, but not a specific indicator of a single disease state 4
- CRP levels can be used to gauge disease severity or predict disease progression and outcome 4
- CRP-guided protocols can be used to guide antibiotic therapy discontinuation among critical care patients, reducing the duration of antibiotic therapy without increasing mortality or infection relapse rates 5
CRP and Infection
- Bacterial infections seem to give the best stimulation to CRP synthesis 2
- CRP is a useful marker to identify patients at risk for bacterial infections, particularly those with Gram-positive cocci, Gram-negative bacilli, and fungal infections 3
- CRP plays a key role in the innate immune system by recognizing pathogens and altered self determinants 6