From the Guidelines
A normal C-reactive protein (CRP) level is generally considered to be less than 3.0 mg/L for high-sensitivity CRP tests (hs-CRP), as this level is associated with low risk of cardiovascular disease 1. When interpreting CRP levels, it's essential to consider the context of other clinical findings and symptoms, as levels can vary based on factors such as age, obesity, medication use, and chronic conditions.
- CRP is an acute phase protein produced by the liver in response to inflammation in the body, serving as a non-specific marker of inflammation.
- Elevated levels indicate that inflammation is present somewhere in the body, but don't pinpoint the exact location or cause.
- Doctors often use CRP levels to monitor inflammatory conditions, infections, or to assess cardiovascular risk.
- Slight elevations (3-10 mg/L) may indicate low-grade inflammation or increased cardiovascular risk, while moderate to severe elevations (above 10 mg/L) typically suggest active infection, injury, or inflammatory disease. The American Heart Association recommends using hs-CRP as the analyte of choice for measuring inflammation, with cutpoints of low risk (less than 1.0 mg/L), average risk (1.0 to 3.0 mg/L), and high risk (3.0 mg/L or higher) 1. It's crucial to note that CRP levels should be interpreted in conjunction with other clinical findings and risk factors, rather than in isolation, to guide treatment decisions and assess cardiovascular risk.
- The measurement of hs-CRP should be performed in a metabolically stable person without obvious inflammatory or infectious conditions, with results expressed as mg/L only.
- Two assays, averaged, fasting or nonfasting, and optimally 2 weeks apart, provide a more stable estimate of the level of this marker 1.
From the Research
Normal C-Reactive Protein (CRP) Levels
- A normal CRP level is generally considered to be less than 10 mg/L in healthy individuals 2.
- High-sensitivity CRP (hsCRP) levels of <1 to <3, and ≥3 mg/L have been suggested to define low-, moderate-, and high-risk groups for cardiovascular events 3.
- CRP values less than 3 mg/L are considered normal in some studies 4.
- Preoperative normal CRP levels are typically less than 10 mg/L 5.
Variations in CRP Levels
- CRP levels can increase to more than 1,000 fold with serious inflammation 2, 6.
- Bacterial infections seem to give the best stimulation to CRP synthesis 2.
- CRP levels can be affected by various factors, including periodontal disease, spinal surgery, and cardiovascular risk 3, 4, 5.
Clinical Significance of CRP Levels
- CRP is a strong independent risk factor for cardiovascular events 3.
- Very low (<0.5 mg/L) and very high (>10 mg/L) levels of hsCRP provide important prognostic information on cardiovascular risk 3.
- CRP is a useful marker for monitoring and understanding the biology of disease, including periodontal disease and cardiovascular disease 6, 4.