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CRP Test & Heart Disease

- Summary
- About CRP tests
- Factors that may affect results
- Abnormal test results
- Frequency of testing
- Questions for your doctor

Reviewed By:
Abdou Elhendy, MD, PhD, FACC, FAHA
Robert I. Hamby, M.D., FACC, FACP
Kerry Prewitt, M.D., FACC

Abnormal CRP test results

The presence of high levels of C-reactive protein (CRP) in the blood means that one or more parts of the body are inflamed. A CRP test cannot determine the location of inflammation or its cause. Therefore, the test is often used in conjunction with other diagnostic tests to confirm a diagnosis related to infection or inflammation.

A conventional CRP test is considered positive for inflammation if it shows CRP levels above 10 milligrams per liter (mg/L). A physician may recommend a different type of CRP test called a high-sensitivity CRP (hs-CRP) assay to identify risk factors for heart disease. An hs-CRP assay is designed to detect inflammation below the levels normally detected with a conventional CRP test.

Hs-CRP levels and risks are interpreted based on studies of individuals who are divided into groups based on their hs-CRP levels (in milligrams per liter [mg/L]). Some studies, for example, create three groups (tertiles), categorizing the risk of heart disease-related events as follows:

Tertile 1: Low risk	< 1.0 mg/L
Tertile 2: Moderate risk	1.0 to 3.0 mg/L
Tertile 3: High risk	> 3.0 mg/L

Other researchers create four groups (quartiles), and even five (quintiles), such as:

Quintile 1: Lowest risk	< 0.55 mg/L
Quintile 2: Low-mid risk	0.55 to 0.99 mg/L
Quintile 3: Mid-high risk	1.0 to 2.1 mg/L
Quintile 4: High-risk	2.1 to 3.8 mg/L
Quintile 5: Highest risk	3.9 to 15 mg/L

Frequency of CRP testing

A C-reactive protein (CRP) test is generally used as a diagnostic tool, especially in cases of suspected heart disease. However, because it cannot identify the specific location of the inflammation, they are usually used in conjunction with other diagnostic tests.

Most patients will not require regular testing and the American Heart Association does not recommend regular CRP tests for people who are at a low risk for cardiovascular disease. However, CRP levels can also be used to monitor the progress of treatments aimed at reducing chronic inflammation. As inflammation in the body decreases, so do CRP levels. Therefore, some patients will have a series of CRP tests performed over the course of their treatment.

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Review Date: 03-06-2007