High-sensitivity C-reactive Protein Test Quick Guide

C-reactive protein (CRP) is a substance found in the blood that increases when there is inflammation within your body, referred to as an acute phase reactant (APC). The high-sensitivity C-reactive protein (hs-CRP) test is more sensitive than the standard CRP test measuring slight increases in CRP levels even when within the normal range. Because of this greater sensitivity, the hs-CRP test can help determine your risk of cardiovascular disease (CVD).

Studies have shown that a single elevated hs-CRP level may be predictive of a myocardial infarction, stroke, peripheral vascular disease, and sudden cardiac death. It may be used in combination with other tests such as a lipid panel or with other cardiac risk markers, including a relatively new biomarker lipoprotein-associated phospholipase A2 (Lp-PLA2) test, to provide added information about heart disease risk.

The American Heart Association identifies three major risk factor categories:

  • Age: Increasing age in both males and females
  • Gender: Though women are at a greater risk of dying, males tend to have more heart attacks
  • Inherited factors: Children of parents with heart disease are more prone to develop it. African-Americans, Mexican-Americans, Native Americans, Native Hawaiians, and some Asian-Americans may be at higher risk.

Diet, smoking, cholesterol levels, blood pressure, physical activity, diabetes, and obesity are other contributing factors. Generally, experts recommend that this test be used if you have a moderate risk of heart attack over the next 10 years.

About the Test

Purpose of the test

Hs-CRP is one of a growing number of cardiac risk markers used to help determine your risk of developing chronic heart disease (CHD). Some studies have shown that measuring CRP with a highly sensitive assay can help identify the risk level for CVD in apparently healthy people.

Normal (<1.0 mg/L) but slightly high levels (1.0 – 3.0 mg/L)  of CRP in otherwise healthy individuals can predict the future risk of a heart attack, stroke, sudden cardiac death, and peripheral arterial disease, even when cholesterol levels are within an acceptable range.

Recent studies have shown hs-CRP could be a marker not only in apparently healthy people but may be useful in predicting risk of death or heart failure in adults with congenital heart disease (ACHD).

What does the test measure?

CRP is a substance that increases in the blood with inflammation and infection as well as following a heart attack, surgery, or trauma. Studies have suggested that a persistent low level of inflammation plays a major role in atherosclerosis, the narrowing of blood vessels due to the build-up of cholesterol and other lipids, often associated with cardiovascular disease (CVD).

The hs-CRP test accurately measures low levels of CRP to identify persistent amounts of CRP that indicate continuing vascular inflammation, thus predicting your risk of developing CVD.

There are two different tests that measure CRP and each one measures a different range of CRP level in the blood for different purposes:

  • The standard CRP test measures markedly high levels of the protein to detect diseases that cause significant inflammation. It measures CRP in the range from 8 to 1000 mg/L. This test may be used to detect inflammation.
  • The hs-CRP test accurately detects lower levels of the protein than the standard CRP test. It measures CRP in the range from 0.3 to 10 mg/L. This test is used to evaluate individuals for risk of CVD.

CVD results in more U.S. deaths each year than any other cause, according to the American Heart Association. Many risk factors, such as family history, high cholesterol, high blood pressure, and excess weight or diabetes, are linked to the development of CVD. But many people with few or no identified risk factors will also develop CVD.

Researchers have looked for additional risk factors that may cause CVD or that could be used to determine lifestyle changes and/or treatments that could reduce CVD risk.

When should I get this test?

Currently, there is no consensus on when to get tested, though some guidelines include recommendations on hs-CRP testing. In a joint committee between the American Heart Association and the CDC, universal hs-CRP screening in adults is not recommended. This test may be most useful in evaluating individuals who have a  10% to 20% chance of having a cardiac event within the next ten years.

It also may be useful for treatment decisions when men and women are older than these respective ages and have LDL-C less than 130 mg/L and meet several other criteria, such as no existing heart disease, diabetes, kidney disease, or inflammatory conditions.

When hs-CRP is evaluated, it has been recommended to have the test repeated to confirm that you have persistent inflammation. The CDC and the American Heart Association (AHA) recommend that measurement of hs-CRP greater than 10 mg/L be repeated twice, optimally two weeks apart, fasting or non-fasting in patients free of infection or acute illness.

Finding a High-sensitivity C-reactive Protein Test

How can I get a High-sensitivity C-reactive Protein Test?

A hs-CRV test is typically ordered by a doctor and conducted in a health care setting by a licensed professional, as a blood draw is required.  While the test can be ordered online, you will still have to go to a testing location to have your blood drawn.

Can I take the test at home?

Under most circumstances, this test can not be taken at home since it requires a blood sample to be taken. While mobile lab services are available in some areas which will collect your sample in your home, typically you will need to go to a professional medical setting to have your sample taken.

How much does the test cost?

The cost of a hs-CRV test depends on several factors, namely whether you are paying out of pocket or have health insurance. The expense may be covered by insurance, depending on your plan. But there may still be charges related to copays and deductibles.

For specific details on expected costs, talk to your doctor or insurance provider.

Taking a High-sensitivity C-reactive Protein Test

A blood sample is required for a hs-CRP test as ordered and conducted by a licensed health care professional. The blood sample is usually drawn from a vein on the inside area of your arm and collected in a special test tube.

Before the test

No test preparation is needed; however, you may be instructed to fast for nine to 12 hours before the blood sample is taken if a lipid panel or a glucose level are to be done at the same time. Ensure your healthcare provider is aware of any medications or other supplements you may be taking.

Some factors that could affect your test results include:

  • Taking statins may have an effect on your CRP level and should be carefully discussed and evaluated by your healthcare practitioner.
  • Women on hormone replacement therapy have been shown to have elevated hs-CRP levels
  • People with chronic inflammation, such as those with arthritis, will already have high CRP levels, so results of the hs-CRP test will not be meaningful

During the test

There are several steps that occur during a needle blood draw:

  1. In a health care setting, a health care professional will locate the vein in your arm from which they will draw blood.
  2. An alcohol wipe is used to clean the area of the arm and allowed to dry before the needle will be inserted.
  3. A rubber band, called a tourniquet, is then placed around your upper arm to make the vein in your arm more visible and easier to access with a needle.
  4. The needle is placed in your vein, and a blood sample tube is attached to the needle which automatically fills with blood. It is possible that you will feel a pinch or a little pain when the needle is inserted.
  5. After the sample vial is filled, the needle and tourniquet are removed.

After the test

Once an adequate amount of blood has been taken, a cotton swab will be applied to the puncture area to minimize further bleeding. An adhesive bandage will be applied. You may be instructed to keep this in place for an hour or more to prevent bruising. If you feel or have a history of lightheadedness, fainting, or nausea, inform the phlebotomist before the procedure. You may be asked to stay seated briefly to monitor you and ensure you are able to safely walk or drive.

High-sensitivity C-reactive Protein Test Results

Receiving test results

The results of a hs-CRV test may be available within a few days after the blood sample arrives at the laboratory, depending on where your sample was collected and the equipment and procedures that are used to conduct the test.

A report with the test results may be shared with you through an online health portal or you may request a physical copy. If the hs-CRV test was ordered by your health care provider, a member of your health care team will likely contact you to discuss the results.

Interpreting test results

Relatively high levels of hs-CRP in otherwise healthy individuals have been linked to an increased risk of heart attack, stroke, sudden cardiac death, and/or peripheral arterial disease, even when cholesterol levels are within an acceptable range.

People with higher hs-CRP values have a more elevated risk of CVD and those with lower values have less risk. Specifically, individuals who have hs-CRP results at the high end of the normal range have 1.5 to four times the risk of having a heart attack as those with hs-CRP values at the low end of the normal range.

The American Heart Association and U.S. Centers for Disease Control and Prevention have defined risk groups as follows:

  • Low risk: less than 1.0 mg/L
  • Average risk: 1.0 to 3.0 mg/L
  • High risk: above 3.0 mg/L

These values are only a part of the total evaluation process for cardiovascular diseases. Additional risk factors to be considered are elevated levels of cholesterol, LDL-C, triglycerides, and glucose. In addition, smoking, high blood pressure (hypertension), and diabetes also increase the risk level.

You may want to ask your doctor a few follow-up questions, such as:

  • Are there medications that could help lower my hs-CRP values?
  • Are there lifestyle changes I should make to help lower the inflammation?
  • Are there other risk factors that I should be aware of?
  • Are there side effects to medications or treatment?



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