C-Reactive Protein (CRP)
Other names: C Reactive Protein, C-Reactive Protein, Quant
What is C-Reactive Protein (CRP)?
C-reactive protein (CRP) is a substance produced by the liver in response to inflammation. Inflammation is a key immune response to infection, injury, or chronic disease. Normally, CRP levels in the blood are low, but they increase when inflammation is present. A CRP test measures these levels to help diagnose or monitor inflammatory conditions.
CRP vs. High-Sensitivity CRP (hs-CRP)
There are two types of CRP tests:
- Standard CRP Test: This test detects significant levels of inflammation, often used to diagnose acute infections or chronic inflammatory diseases like rheumatoid arthritis and lupus.
- High-Sensitivity CRP (hs-CRP) Test: This more sensitive test can detect minor increases in CRP and is used primarily to assess the risk of cardiovascular diseases. Even small elevations in hs-CRP levels can indicate the risk of heart disease or stroke.
Why CRP Tests Are Done
Healthcare providers may order a CRP test for several reasons:
- Infection Detection: To check for bacterial or viral infections.
- Chronic Inflammatory Diseases: To diagnose conditions such as rheumatoid arthritis, lupus, or inflammatory bowel diseases (Crohn’s disease and ulcerative colitis).
- Heart Disease Risk: The hs-CRP test helps assess the risk of coronary artery disease. Elevated CRP levels are linked to a higher likelihood of heart attacks or strokes.
- Monitoring Treatment: CRP tests are also used to track the effectiveness of treatments for chronic inflammatory conditions or infections.
How is the Test Performed?
A CRP test requires a simple blood draw from a vein, usually in the arm. The procedure is quick, and no special preparation is needed. However, it's important to inform your healthcare provider about any medications you are taking, as certain drugs (like NSAIDs) can affect CRP levels.
Understanding Test Results
CRP levels are measured in milligrams per liter (mg/L), and results can vary depending on the lab. Here's a general guide:
-
Standard CRP Test Results:
- Less than 8-10 mg/L: Normal or low inflammation.
- Greater than 10 mg/L: Indicates significant inflammation due to infection, injury, or a chronic inflammatory disease.
-
hs-CRP Test Results (for cardiovascular risk):
- Low risk: Less than 1.0 mg/L.
- Moderate risk: 1.0-3.0 mg/L.
- High risk: Greater than 3.0 mg/L.
Factors Affecting CRP Levels
CRP levels can fluctuate for reasons unrelated to serious health conditions, such as:
- Smoking
- Obesity
- Recent infections or injuries
- Pregnancy
- Hormonal changes (e.g., from birth control pills)
It's important to note that elevated CRP levels don't pinpoint the exact location or cause of inflammation. Further testing is often required to determine the underlying issue.
CRP and Heart Disease
While high CRP levels are linked to an increased risk of heart disease, the test alone doesn’t diagnose heart conditions. Healthcare providers assess CRP results alongside other risk factors like cholesterol levels, family history, and lifestyle to get a comprehensive understanding of a person's cardiovascular risk.
People with moderately elevated hs-CRP levels (2.0 mg/L or higher) may be at higher risk of heart attacks, especially if they have other risk factors like high cholesterol, diabetes, or smoking habits.
What to Do if You Have High CRP Levels
If your CRP levels are high, your healthcare provider will likely recommend lifestyle changes, such as:
- Adopting a heart-healthy diet
- Engaging in regular physical activity
- Managing diabetes and high blood pressure
- Quitting smoking
- Taking cholesterol-lowering medications like statins if necessary
Takeaways
A CRP test is a useful tool for detecting inflammation in the body and assessing the risk of heart disease. While elevated CRP levels indicate inflammation, they do not specify the cause. Further diagnostic tests are often necessary to determine the underlying issue and guide treatment.
By understanding CRP test results in conjunction with other health assessments, you and your healthcare provider can take steps to improve your health and lower the risk of cardiovascular events.
References:
-
Black, S., Kushner, I., & Samols, D. (2004). C-reactive protein and its role in the diagnosis of inflammatory diseases. Journal of Clinical Pathology, 57(10), 1048-1054. https://doi.org/10.1136/jcp.2003.007282
-
Ridker, P. M., Rifai, N., Rose, L., Buring, J. E., & Cook, N. R. (2002). Comparison of C-reactive protein and low-density lipoprotein cholesterol levels in the prediction of first cardiovascular events. New England Journal of Medicine, 347(20), 1557-1565. https://doi.org/10.1056/NEJMoa021993
-
Pepys, M. B., & Hirschfield, G. M. (2003). C-reactive protein: A critical update. Journal of Clinical Investigation, 111(12), 1805-1812. https://doi.org/10.1172/JCI200318921
-
Pearson, T. A., Mensah, G. A., Alexander, R. W., Anderson, J. L., Cannon III, R. O., Criqui, M., ... & Smith, S. C. (2003). Markers of inflammation and cardiovascular disease: Application to clinical and public health practice: A statement for healthcare professionals from the Centers for Disease Control and Prevention and the American Heart Association. Circulation, 107(3), 499-511. https://doi.org/10.1161/01.CIR.0000052939.59093.45
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Ballou, S. P., & Lozanski, F. B. (1992). Induction of inflammatory cytokine release from cultured human monocytes by C-reactive protein. Cytokine, 4(5), 361-368. https://doi.org/10.1016/1043-4666(92)90048-8
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Danesh, J., Wheeler, J. G., Hirschfield, G. M., Eda, S., Eiriksdottir, G., Rumley, A., ... & Pepys, M. B. (2004). C-reactive protein and other circulating markers of inflammation in the prediction of coronary heart disease. New England Journal of Medicine, 350(14), 1387-1397. https://doi.org/10.1056/NEJMoa032804
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Gabay, C., & Kushner, I. (1999). Acute-phase proteins and other systemic responses to inflammation. New England Journal of Medicine, 340(6), 448-454. https://doi.org/10.1056/NEJM199902113400607
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Ridker, P. M. (2016). C-reactive protein and the prediction of cardiovascular events among those at intermediate risk: Moving an inflammatory hypothesis toward consensus. Journal of the American College of Cardiology, 27(20), 2092-2095. https://doi.org/10.1016/j.jacc.2016.07.078
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Kaptoge, S., Di Angelantonio, E., Lowe, G., Pepys, M. B., Thompson, S. G., Collins, R., & Danesh, J. (2010). C-reactive protein concentration and risk of coronary heart disease, stroke, and mortality: An individual participant meta-analysis. The Lancet, 375(9709), 132-140. https://doi.org/10.1016/S0140-6736(09)61717-7
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Yudkin, J. S., Kumari, M., Humphries, S. E., & Mohamed-Ali, V. (2000). Inflammation, obesity, stress, and coronary heart disease: Is interleukin-6 the link? Atherosclerosis, 148(2), 209-214. https://doi.org/10.1016/S0021-9150(99)00463-3
What does it mean if your C-Reactive Protein (CRP) result is too high?
Elevated levels of C-Reactive Protein (CRP) are indicative of inflammation in the body. CRP is a substance produced by the liver in response to inflammation, and its levels in the blood increase when there is inflammation in the body.
Conditions Associated with Elevated CRP:
→ Infections: Bacterial, viral, and fungal infections can cause elevated CRP levels.
→ Chronic inflammatory diseases: Conditions such as rheumatoid arthritis, lupus, and inflammatory bowel disease.
→ Cardiovascular diseases: High levels of CRP are associated with an increased risk of heart disease and stroke.
→ Autoimmune diseases: Diseases such as lupus and vasculitis.
→ Cancer: Certain types of cancer can elevate CRP levels.
→ Obesity: Increased body fat can raise CRP levels.
→ Diabetes: Both type 1 and type 2 diabetes can be associated with elevated CRP.
→ Chronic kidney disease: CRP levels can be elevated in kidney disease.
→ Trauma or injury: Physical injury can lead to increased CRP levels.
Possible Reasons for Elevation:
→ Acute or chronic inflammation: This is the most common reason for elevated CRP.
→ Infections: Any active infection in the body can raise CRP levels.
→ Surgery: Post-operative patients often have elevated CRP due to the body’s response to surgery.
→ Lifestyle factors: Smoking, lack of physical activity, and poor diet can contribute to higher CRP levels.
→ Stress: Both physical and emotional stress can lead to increased CRP.
→ Obesity: Adipose tissue produces inflammatory cytokines, which can raise CRP levels.
Potential Treatment Considerations:
- Treat underlying conditions: Managing chronic diseases such as diabetes, hypertension, and autoimmune disorders can reduce CRP levels.
- Anti-inflammatory medications: Nonsteroidal anti-inflammatory drugs (NSAIDs) and corticosteroids can reduce inflammation and CRP levels.
- Lifestyle changes: Regular physical activity, a healthy diet, weight loss, and smoking cessation can help lower CRP.
- Supplements: Omega-3 fatty acids, antioxidants, and certain vitamins have been shown to help reduce inflammation.
Other Biomarkers Correlated with CRP:
- Erythrocyte Sedimentation Rate (ESR): Another marker of inflammation.
- Interleukin-6 (IL-6): A cytokine involved in inflammation.
- Tumor Necrosis Factor-alpha (TNF-α): Another cytokine that plays a role in systemic inflammation.
- Fibrinogen: An acute-phase protein that is elevated in response to inflammation.
- Procalcitonin: Especially in bacterial infections.
Nutrient Associations:
- Omega-3 fatty acids: Found in fish oil, these can reduce inflammation.
- Antioxidants: Vitamins C and E, as well as polyphenols found in fruits and vegetables, can have anti-inflammatory effects.
- Vitamin D: Deficiency is associated with higher levels of inflammation.
- Magnesium: Adequate magnesium intake is linked to lower CRP levels.
- Fiber: High-fiber diets are associated with lower levels of CRP.
Specific Considerations:
- Males vs. Females: CRP levels can be slightly higher in females compared to males, partly due to hormonal differences.
- Young vs. Old: CRP levels tend to increase with age. Older adults are more likely to have elevated CRP due to chronic diseases and overall higher inflammation levels.
References:
- Ridker, P. M., et al. (2000). "C-reactive protein levels and outcomes after statin therapy." New England Journal of Medicine, 352(1), 20-28.
- Pepys, M. B., & Hirschfield, G. M. (2003). "C-reactive protein: a critical update." Journal of Clinical Investigation, 111(12), 1805-1812.
- Pearson, T. A., et al. (2003). "Markers of inflammation and cardiovascular disease: application to clinical and public health practice." Circulation, 107(3), 499-511.
- Kaptoge, S., et al. (2010). "C-reactive protein concentration and risk of coronary heart disease, stroke, and mortality: an individual participant meta-analysis." Lancet, 375(9709), 132-140.
- Danesh, J., et al. (2004). "C-reactive protein and other circulating markers of inflammation in the prediction of coronary heart disease." New England Journal of Medicine, 350(14), 1387-1397.
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What does it mean if your C-Reactive Protein (CRP) result is too low?
Low or normal CRP levels indicate little to no inflammation in the body, suggesting the absence of significant infection, injury, or chronic inflammatory conditions. This is generally a sign of good health or effective treatment for an existing inflammatory condition.
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