A substance called C-reactive protein (CRP) is produced by the liver in response to inflammation. This protein belongs to a class of proteins called Acute Phase Reactants, which are released by the immune system when it detects inflammation. Elevated CRP levels may also indicate the presence of inflammation in the coronary arteries, thereby increasing the risk of cardiovascular disease. Here is a detailed understanding of the CRP test.

What is a C-reactive Protein Test (CRP)?

The CRP test measures the concentration of a protein known as CRP in the bloodstream, which is produced by the liver. Blood levels of CRP may be elevated when an individual is experiencing inflammation or infection. Reactive protein C is utilised for infection monitoring since CRP levels often rise before the onset of symptoms like pain or fever and decrease as the person recovers.

Purpose of the CRP Blood test

A C-reactive protein test is typically ordered by healthcare providers to assist in the identification or exclusion of certain conditions, such as:

• Infection - Individuals exhibiting inflammatory symptoms such as fever, chills, nausea, redness or swelling, vomiting, rapid breathing, or a rapid heart rate.
• Treatment of Sepsis - This potentially life-threatening condition occurs when the immune system reacts to an infection with a bacterial microorganism, leading to systemic inflammation.
• Monitoring the development of autoimmune diseases, including Rheumatoid Arthritis and Lupus (Systemic Lupus Erythematosus).
• Determining the treatment of chronic inflammatory diseases.
• Checking for some types of arthritis

A CRP blood test is used to monitor patients after surgery or invasive procedures, aiming to determine if they have developed an infection during the recovery period. Since a CRP test cannot diagnose a specific disease or pinpoint the location of inflammation in the body, healthcare providers often order additional tests when the CRP levels are high.

Who performs a CRP test?

Phlebotomists are the primary healthcare providers responsible for conducting blood draws; however, any qualified healthcare professional like doctors or nurses can perform this task. The collected blood samples are then sent to a laboratory, where medical laboratory scientists are responsible for preparing the samples and conducting the analysis using machines known as analyzers.

Uses of CRP Test 

A CRP test is utilized to detect or monitor inflammation in both acute and chronic conditions, Include:

• Infections caused by bacteria or viruses
• Inflammatory bowel diseases like Crohn's disease and ulcerative colitis
• Autoimmune disorders such as lupus, rheumatoid arthritis, and vasculitis
• Respiratory conditions like asthma

The CRP test can be used by medical professionals to evaluate the efficacy of therapy for chronic inflammation or to help them decide how best to treat patients who have sepsis, a serious and potentially fatal reaction to an infection that has entered the bloodstream.

How is a CRP Test Done?

CRP tests can be performed at a healthcare facility, local hospital, clinic, or specialised diagnostic lab. The process typically involves selecting a vein, usually located near the elbow, and attaching an elastic band to the upper arm to allow the vein to swell. An alcohol swab is then used to clean the skin. A needle is inserted into the vein, and blood is drawn. Afterward, the elastic band is removed, and the needle is taken out. The entire process typically takes no more than five minutes.

Risks

A blood test is one of the most common and essential medical tests and screenings. There is usually little to no risk associated with a blood test. Some individuals may experience mild pain or bruising at the site where the needle was inserted, but these symptoms typically disappear very quickly.

What Does a CRP Measure?

A CRP blood test analyses a sample of a person's blood to determine the presence and severity of inflammation. The results of the CRP test provide healthcare providers with information about the underlying condition. However, the test does not identify the source of the inflammation or its underlying cause. The high-sensitivity CRP (h-CRP) test can be used to assess the risk of heart disease, even in individuals who appear to be in good health. It is capable of detecting significantly lower levels of CRP than the standard CRP test.

What does a low CRP level mean?

A CRP level below 0.9 mg/dL is considered normal, so there is no "lower than normal" range. If your CRP levels have decreased from a previously high result, it suggests that inflammation in your body may be reduced, or that the treatment for inflammation is effective.

CRP Results 

The results of the test may take few days to become available. The healthcare providers can provide an explanation of the results. The concentration of C-reactive protein (CRP) in the blood is typically measured in mg/L or mg/deciliter. 

A slight increase in the concentration of CRP, between 0.3 mg/dL and 1 mg/dL, does not necessarily indicate the presence of a disease that requires treatment. High test results are those with a concentration of 8 mg/L or greater than 10 mg/L. The range of C reactive protein test results may vary depending on the laboratory conducting the test.

When would I need a C-reactive protein (CRP) test?

A CRP test may be prescribed by the physician if the patient is exhibiting signs of a severe bacterial infection, such as:

• Fever
• Chills
• Nausea and vomiting
• Rapid breathing
• Rapid heart rate

What do Abnormal Results Mean?

The range of results for this test depends on the laboratory and the methodology used. Generally, a CRP concentration below 9 mg/L is considered in C reactive protein normal ranges. If the CRP concentration in the blood exceeds this level, it may indicate an inflammatory response to a substance. To identify the source of the inflammation, further testing may be necessary.

A CRP test result that exceeds 10 milligrams per deciliter (mg/dL) is typically seen as a significant increase. This result may indicate any of the following conditions:

• Viral infections
• Acute bacterial infections
• Systemic vasculitis
• Major injury

If CRP blood test results are above 50 mg/L, it's considered a substantial elevation. In most cases, higher readings are associated with acute bacterial infections.

What should you do if you have high CRP?

Doctors refer to a high level of C-reactive protein as a biomarker. While a biomarker is an element to consider when assessing a person's health, it is not a single indicator of a specific diagnosis. For the treatment of high C-reactive protein levels, consuming a diet rich in dietary fibre, fruits, and vegetables can help reduce CRP concentrations. If an individual is at a high risk of developing cardiovascular disease, and the test results show elevated CRP levels, a healthcare provider may recommend cholesterol-lowering drugs, such as statins. Vitamin C is also used to reduce CRP levels in the blood of people at higher risk of heart disease.

Conclusion

A CRP blood test is designed to assess the level of inflammation in the human body. An elevated CRP level may indicate an underlying medical condition or an increased risk of cardiovascular disease. Patients with elevated CRP levels should consult a doctor to determine the best course of action to reduce the likelihood of serious health complications

FAQs

Q1. What happens when CRP levels are high? 

Ans. High CRP levels may indicate a significant health problem associated with inflammation. The body uses inflammation as a mechanism to defend its tissues and accelerate healing after an accident, infection, or illness.

Q2. Can the CRP test detect viral infections? 

Ans. The CRP test is useful for identifying and monitoring elevated CRP levels caused by viral infections. It can help detect various viral infections that trigger inflammation and raise CRP levels.

Q3. Why should someone get a CRP test? 

Ans. Those experiencing any of the following signs of a bacterial infection may need this test:

• Fever
• Nausea and vomiting
• Rapid breathing
• Rapid heart rate

Q4. Does the test carry any risks? 

Ans. Undergoing a blood test is highly unlikely to cause harm. While minor bruising or soreness at the needle insertion site is possible, most adverse effects are rare.

Reference:

https://my.clevelandclinic.org/health/diagnostics/23056-c-reactive-protein-crp-test