When to draw High-Sensitivity C-Reactive Protein (hsCRP)?

From the Guidelines

High-sensitivity C-reactive protein (hsCRP) should be drawn when assessing cardiovascular risk in intermediate-risk patients or when evaluating for inflammation, as it provides valuable information for guiding further evaluation and therapy in the primary prevention of cardiovascular disease (CVD) 1. When to draw hsCRP is a critical decision that depends on various factors, including the patient's cardiovascular risk profile and the presence of inflammation.

Key Considerations

• hsCRP is an independent marker of risk that may be used at the discretion of the physician in patients judged by global risk assessment to be at intermediate risk (10% to 20% risk of coronary heart disease [CHD] per 10 years) for CVD 1.
• The test is most useful for individuals with a 10-year cardiovascular risk of 5-20% who might benefit from more aggressive preventive therapy if elevated levels are found.
• hsCRP should be measured when the patient is metabolically stable, without acute illness or recent trauma, as these conditions can temporarily elevate levels 1.
• The test should be performed after a 9-12 hour fast, with two measurements taken 2 weeks apart to establish baseline levels, as a single elevated reading may not reflect chronic inflammation.

Interpretation of Results

• Values less than 1 mg/L indicate low cardiovascular risk, 1-3 mg/L moderate risk, and greater than 3 mg/L high risk 1.
• hsCRP is particularly valuable when combined with lipid testing, as it provides complementary information about inflammation-related cardiovascular risk that cholesterol testing alone cannot detect.
• The test works by measuring low levels of CRP with greater precision than standard CRP tests, allowing detection of subtle chronic inflammation associated with atherosclerosis.

Clinical Implications

• The use of hsCRP as an independent predictor of increased coronary risk is supported by the best evidence to date, and it may be used to identify patients without known CVD who may be at higher absolute risk than estimated by major risk factors 1.
• However, treatment of patients with elevated hsCRP on the basis of the hsCRP alone has limited data to support it at the present time, and would require a prospective clinical trial to prove efficacy.

From the Research

When to Draw hsCRP

• hsCRP should be drawn in patients with intermediate or high risk of coronary heart disease, as recommended by the American Heart Association 2
• It is also recommended to draw hsCRP in patients with type 2 diabetes mellitus, as elevated hsCRP levels are associated with increased risk of cardiovascular disease and beta-cell dysfunction 2, 3
• hsCRP levels can be used to predict the risk of cardiovascular disease, with levels of less than 1 mg/L indicating low risk, 1-3 mg/L indicating intermediate risk, and greater than 3 mg/L indicating high risk 2, 4
• In patients with diabetes mellitus, hsCRP levels are associated with increased risk of type 2 diabetes development, and are also correlated with hemoglobin A1c levels and future cardiovascular risk 2
• The measurement of hsCRP can be useful in primary prevention, as it can identify individuals at high risk of atherosclerotic cardiovascular disease, even in those with low levels of atherogenic lipid measures 5

Clinical Importance of hsCRP

• hsCRP is a marker of inflammation that predicts incident myocardial infarction, stroke, peripheral arterial disease, and sudden cardiac death among healthy individuals with no history of cardiovascular disease 4
• hsCRP confers additional prognostic value at all levels of cholesterol, Framingham coronary risk score, severity of the metabolic syndrome, and blood pressure 4
• Elevated hsCRP levels are associated with advanced stage beta-cell dysfunction and insulin resistance in patients with type 2 diabetes mellitus 3

hsCRP and Cardiovascular Risk

• hsCRP is independently associated with atherosclerotic cardiovascular disease, regardless of atherogenic lipid levels and pooled cohort equation risk score in individuals without known cardiovascular disease 5
• The association between hsCRP and cardiovascular risk is consistent among individuals with low or high estimated risk by the pooled cohort equation 5