Is cardiac C-Reactive Protein (CRP) the same as high sensitivity C-Reactive Protein (hs-CRP)?

From the Guidelines

Cardiac-CRP and high sensitivity-CRP (hs-CRP) are not the same, though they are related concepts, with cardiac-CRP referring to C-reactive protein measured in the context of cardiac evaluation and hs-CRP referring to the testing method that can detect very low levels of CRP in the blood. The distinction between these two terms is important because the appropriate test must be ordered to accurately assess cardiac risk. The hs-CRP test is the actual laboratory assay that can measure CRP at concentrations as low as 0.1-0.3 mg/L, which is necessary for cardiovascular risk assessment 1. Traditional CRP tests can only reliably detect levels above 3-5 mg/L, which is useful for monitoring infection or inflammation but not sensitive enough for cardiac risk stratification.

Key Differences

• Cardiac-CRP is a term used to describe the measurement of C-reactive protein in the context of cardiac evaluation
• High sensitivity-CRP (hs-CRP) is a specific testing method that can detect very low levels of CRP in the blood
• The American Heart Association suggests that hs-CRP levels below 1 mg/L indicate low cardiovascular risk, 1-3 mg/L indicate moderate risk, and above 3 mg/L indicate high risk 1

Clinical Implications

• When doctors order a "cardiac CRP," they are typically requesting an hs-CRP test to evaluate cardiovascular risk
• The use of hs-CRP as an independent predictor of increased coronary risk is supported by the best evidence to date 1
• The measurement of hs-CRP may be useful in the estimation of prognosis in patients who need secondary preventive care, such as those with stable coronary disease or acute coronary syndromes 1

From the Research

Cardiac-CRP and High Sensitivity-CRP

• Cardiac-CRP and high sensitivity-CRP (hs-CRP) are related but not exactly the same, as hs-CRP is a biomarker used for risk prediction for cardiovascular disease by assessing low concentration of inflammation 2.
• Measurements of regular CRP have become very sensitive with a lower detection limit of 0.3 mg/L, which can replace the costlier hs-CRP measurements in the lower range 2.
• The correlation between CRP and hs-CRP was significant (P < 0.001), with a Spearman regression R2 = 0.98, indicating a high correlation between the two 2.

Differences and Similarities

• A Bland-Altman plot displayed an average difference of 0.19 mg/L (95%CI, 0.17 to 0.23) between the CRP and hs-CRP, demonstrating a small difference between the two measurements 2.
• The use of hs-CRP in cardiovascular disease risk stratification and management is becoming common in clinical practice, with updated screening guidelines and the Reynolds Risk Score incorporating hs-CRP and family history with standard cardiovascular risk factors 3.
• Statins have been shown to decrease the vascular events among persons with elevated hs-CRP by half, even when cholesterol levels are low, highlighting the importance of hs-CRP in cardiovascular risk assessment 3.

Clinical Applications

• The measurement of CRP using both standard and high-sensitivity CRP (hs-CRP) assays is becoming common in clinical practice, with applications in cardiology, gastroenterology, rheumatology, infectious diseases, and oncology 3.
• A decision analytic Markov model was used to compare the cost-effectiveness of using hs-CRP to identify intermediate- and low-cardiovascular-risk individuals for statin therapy, with results indicating that risk-based treatment without hs-CRP testing is more cost-effective 4.
• Elevated hs-CRP in acute myocardial infarction (AMI) patients undergoing percutaneous coronary intervention (PCI) has prognostic value for future cardiovascular events, with the prognostic effect of baseline hs-CRP mostly confined to the first 6 months after AMI 5.
• Statins have been shown to reduce the serum levels of hs-CRP and CRP in patients with cardiovascular diseases, with high-intensity statin treatment decreasing serum levels of CRP in CVDs patients 6.