An overview of C-reactive protein test
A C-reactive protein (CRP) test is a blood test that measures the level of CRP in your blood. CRP is a protein produced by the liver that increases when there's inflammation in the body. The test can help identify inflammation, infections, or chronic inflammatory diseases such as rheumatoid arthritis or lupus. The high-sensitivity C-reactive protein (hs-CRP) test is more sensitive than a standard test and can help assess the risk of coronary artery disease and the possibility of a second heart attack. However, it's essential to note that an hs-CRP test isn't suitable for everyone, and a high level of CRP can be caused by factors unrelated to heart health. Your healthcare provider can help determine if a CRP test is appropriate for you based on your individual risk factors and medical history.
What is C-reactive protein test used for?
A C-reactive protein (CRP) test is used to check the level of CRP in the blood. CRP is a protein made by the liver, and its level increases when there's inflammation in the body. The test is used for various purposes, including:
- Checking for infection: A high CRP level can indicate the presence of an infection.
- Diagnosing chronic inflammatory diseases: A CRP test can help diagnose chronic inflammatory diseases such as rheumatoid arthritis or lupus.
- Assessing heart disease risk: A high-sensitivity C-reactive protein (hs-CRP) test is used to determine the risk of coronary artery disease, a condition where the arteries of the heart narrow, potentially leading to a heart attack.
- Evaluating the risk of a second heart attack: An hs-CRP test can help assess the risk of experiencing a second heart attack for those who have already had one.
It is important to note that an hs-CRP test is not suitable for everyone and should be interpreted with caution. A high hs-CRP level does not always indicate heart disease and can be influenced by various factors such as lifestyle, medications, and other health conditions. Your healthcare provider will help determine if a CRP test is appropriate for you based on your individual risk factors and medical history.
How often should C-reactive protein test be performed?
The frequency of C-reactive protein (CRP) tests may vary depending on the individual's medical history and risk factors. Typically, a CRP test may be done once to check for infection, help diagnose a chronic inflammatory disease, or assess heart disease risk. However, it is important to note that the test results for CRP can vary over time, and a coronary artery disease risk assessment should ideally be based on the average of two hs-CRP tests taken two weeks apart. This is to ensure a more accurate assessment of the individual's risk for heart disease. Your healthcare provider can provide specific guidance on how often you should undergo CRP testing based on your unique health situation.
How to prepare for C-reactive protein test?
To prepare for a C-reactive protein (CRP) test, you should follow these steps:
- Inform your health care provider about any medications you are taking, including over-the-counter drugs and supplements.
- If you need to fast before the test, follow your health care provider's instructions. For example, if you're having an hs-CRP test to check for heart disease, you might need to fast for a period of time.
- Avoid strenuous exercise before the test, as it can increase CRP levels.
- Let your health care provider know if you have any allergies or medical conditions that may affect the test. Follow your health care provider's specific instructions regarding preparation for the test.
How is C-reactive protein test conducted?
A C-reactive protein (CRP) test is conducted by taking a sample of your blood. A health care provider typically performs the test by inserting a needle into a vein in your arm, usually at the bend of the elbow. The blood sample is then sent to a lab for analysis. The process is usually quick, and you can resume your normal activities immediately after the test.
How are C-reactive protein test results reported?
C-reactive protein (CRP) test results are typically reported in milligrams per liter (mg/L). A high test result, which indicates inflammation in the body, is generally considered to be equal to or greater than 8 mg/L or 10 mg/L, depending on the lab conducting the test. The results can provide insight into a person's risk of heart disease, with values below 2.0 mg/L indicating a lower risk, and values equal to or greater than 2.0 mg/L indicating a higher risk. For a more accurate assessment of coronary artery disease risk, it is recommended to average the results of two hs-CRP tests taken two weeks apart.
Understanding the report
C-reactive protein (CRP) test results are interpreted based on the levels of CRP in the blood. A high-sensitivity C-reactive protein (hs-CRP) test is more sensitive than a standard C-reactive protein test. In general, results for an hs-CRP test are given as follows:
- Lower risk of heart disease: Less than 2.0 mg/L
- Higher risk of heart disease: Equal to or greater than 2.0 mg/L
A CRP level of 8 mg/L or 10 mg/L is considered high. A high test result indicates inflammation in the body, which may be due to serious infection, injury, or chronic disease. Your healthcare provider may recommend other tests to determine the cause. A person's CRP levels vary over time. A coronary artery disease risk assessment should be based on the average of two hs-CRP tests, taken two weeks apart. Values above 2.0 mg/L may indicate an increased risk of heart attacks or risk of a repeat heart attack. In summary, CRP test results are interpreted by measuring the levels of CRP in the blood, with lower values indicating a lower risk of heart disease and higher values indicating a higher risk. Your healthcare provider can help you understand the significance of your test results and recommend appropriate follow-up actions.
Limitations and Considerations
Limitations of the C-reactive protein test include:
- Indicating inflammation, rather than its cause: A high CRP level can be an indicator of inflammation, but it doesn't pinpoint the specific cause. Additional tests may be required to identify the underlying cause of inflammation.
- Not specific to cardiovascular disease: While a high-sensitivity CRP test can help assess the risk of heart disease, it may not be specific to cardiovascular disease. Other conditions, such as infections or chronic inflammatory diseases, can also result in elevated CRP levels.
- Results can vary between labs: The range of normal CRP levels can vary depending on the laboratory performing the test. This may lead to discrepancies in the interpretation of test results.
- Inflammation can be temporary: CRP levels can fluctuate over time and may be influenced by short-term factors like exercise or infections. Therefore, a single test may not accurately reflect long-term inflammation levels.
- Not recommended for everyone: An hs-CRP test may not be suitable for everyone, especially those with a low risk of heart disease or those who have already had a heart attack and have average CRP levels. In such cases, the test may not provide additional information for risk assessment.
- Not diagnostic: A CRP test is not diagnostic but rather a screening tool. It helps identify potential risk factors, and further testing and evaluation may be required for a definitive diagnosis. It's important to consult with a healthcare provider to determine whether a CRP test is appropriate for an individual's specific health context.