What is the difference between C-Reactive Protein (CRP) and high-sensitivity C-Reactive Protein (hsCRP)?

Difference Between CRP and hsCRP

The main difference between standard CRP and hsCRP is the detection limit - hsCRP can accurately measure concentrations as low as 0.3 mg/L, while standard CRP has a lower reporting limit of 3 mg/L, making hsCRP specifically suitable for cardiovascular risk assessment in apparently healthy individuals. 1

Technical Differences

• Detection Range:

  • hsCRP: Accurately measures concentrations down to 0.3 mg/L
  • Standard CRP: Lower reporting limit of 3 mg/L

• Clinical Applications:

  • hsCRP: Used to assess low-grade inflammation associated with atherosclerotic risk
  • Standard CRP: Used to detect acute inflammation and infection (10-40 mg/L for mild inflammation, 40-200 mg/L for acute inflammation) 1

• Analytical Methods:

  • Both tests measure the same protein but use different analytical techniques with different sensitivities
  • Both are typically calibrated to WHO 1st International Standard 85/506 or Certified Reference Material 470 1

Clinical Utility

Cardiovascular Risk Assessment

• hsCRP is recommended for cardiovascular risk assessment in patients with moderate risk profiles (10-20% risk of CHD per 10 years) 2
• Risk stratification using hsCRP:
  • Low risk: <1.0 mg/L
  • Average risk: 1.0-3.0 mg/L
  • High risk: >3.0 mg/L 1

Acute Inflammation

• Standard CRP is sufficient and more cost-effective for diagnosing acute inflammatory conditions 1
• For acute coronary syndromes, a cutpoint of 10 mg/L may have better predictive qualities, whereas 3 mg/L may be more useful in patients with stable coronary disease 2

Correlation Between Tests

Recent research shows high correlation between standard CRP and hsCRP measurements in the lower ranges:

• Agreement of 91.4% between CRP and hsCRP risk group classifications (kappa 0.87)
• Average difference of only 0.19 mg/L between measurements
• This suggests standard CRP tests can potentially replace costlier hsCRP measurements in many clinical scenarios 3

Clinical Practice Recommendations

• For cardiovascular risk assessment, use hsCRP to evaluate low-grade inflammation in apparently healthy individuals 1
• Two separate measurements of hsCRP taken 2 weeks apart are adequate to classify a person's risk level 2
• Patients with persistently unexplained marked elevation of hsCRP (>10 mg/L) after repeated testing should be evaluated for non-cardiovascular causes 2
• hsCRP should not be used for serial testing to monitor effects of treatment 2

Important Considerations

• Multiple factors can affect CRP levels including age, sex, BMI, smoking status, exercise, diet, and underlying inflammatory conditions 1
• Both very low (<0.5 mg/L) and very high (>10 mg/L) levels of hsCRP provide important prognostic information on cardiovascular risk 4
• The European Society of Cardiology guidelines (2012) state that hsCRP may be measured as part of refined risk assessment in patients with an unusual or moderate CVD risk profile, but should not be measured in asymptomatic low-risk individuals and high-risk patients 2

In summary, while both tests measure the same protein, hsCRP's ability to detect lower concentrations makes it valuable for cardiovascular risk assessment, while standard CRP remains appropriate for evaluating acute inflammatory conditions.