C-Reactive Protein (CRP)

A CRP test is a measure of the levels of C-reactive protein in the body. The liver releases this protein in the body in response to inflammation. This means that when the immune system is activated, say after bacterial, viral or parasitic infection, it sends out mediators composed of cytokines and inflammatory cells that can be measured through CRP test.

The function of these mediators is to trap bacteria and other microorganisms and to start healing the injured tissues. Consequently, there is pain, redness, swelling and bruising as these mediators perform their task. Normally, the levels of CRP in the blood are low. Only in case of serious infection and inflammatory conditions, these levels rise up to a moderate or severe level.

CRP test uses

A CRP blood test is used to analyze and assess the presence and severity of inflammation in the body. Healthcare providers also perform this test in order to diagnose certain conditions, including:

• Forms of arthritis
• Fungal infections
• Severe bacterial infections that can result in sepsis
• Bone infections like osteomyelitis
• Pelvic inflammatory disease (PID)
• Inflammatory bowel disease (IBD)
• Autoimmune disorders like lupus (SLE), rheumatoid arthritis (RA)
• To check for infection following surgery

A CRP test alone is insufficient to make a diagnosis, which is why most healthcare providers order this test along with other investigations to help make a diagnosis.

When is a CRP test required?

Patients with the following symptoms may be asked to get a CRP test by their doctor:

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

In addition to making a diagnosis, CRP test is also done to monitor the response to therapy especially for people already diagnose with a chronic inflammatory condition.

Who performs a CRP test?

A CRP test is performed by a phlebotomist who draws blood under aseptic conditions in the laboratory. Thereafter, the samples are processed and sent to the machines known as analyzers.

What to expect during the testing?

This five-minute procedure involves:

• Sitting the patient down comfortably in a chair in the laboratory or hospital
• Checking the arms for an easily accessible vein
• Once a vein is located, the skin is disinfected before drawing a sample
• A small needle is inserted in the vein to draw a blood sample. This sample is collected in a test tube
• Once sufficient amount of blood is collected from the vein, the needle is removed and a cotton ball is applied with pressure on the site to stop the bleeding
• A bandage is then placed to cover the site where the blood is drawn from

What to expect after the testing?

Following the drawing of blood, the sample is sent for processing to the laboratory and the patient is free to go. The results are shared with the patient soon thereafter.

What are the risks of CRP test?

The risks of drawing blood, especially for CRP test are very minimal. Such investigations form a regular part of medical testing and screening. There can be slight tenderness and bruise at the site where blood is drawn from, which usually gets better quickly. Despite it being a common and routine procedure, care is taken to disinfect the skin before drawing blood, and using sterilized equipment for sampling.

CRP normal range

The reference range for normal CRP levels can vary between different laboratories. Along with the results of the testing, there is also a reference range provided for convenience of interpretation of results. Generally, the normal level of CRP is about 0.9 mg/dl.

Minor rise in the CRP levels can be seen due to:

• Obesity
• Smoking
• Common cold
• Depression
• Diabetes
• Insomnia
• Recent injury or trauma
• Periodontitis
• Pregnancy

Women and the elderly population naturally have raised levels of CRP in comparison to men and children.

What does a high CRP level indicate?

Moderate to severe elevation of CRP indicate ongoing inflammation in the body. However, this investigation cannot further detail the site or cause of inflammatory response in the body. This is why most healthcare providers get additional testing to localize the source of high CRP in patients.