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

Difference Between High Sensitivity CRP and CRP

The main difference between high sensitivity CRP (hsCRP) and standard CRP is the detection limit - hsCRP assays can accurately measure concentrations down to 0.3 mg/L, while standard CRP assays typically have a lower reporting limit of 3 mg/L, making hsCRP more suitable for cardiovascular risk assessment in apparently healthy individuals. 1

Technical Differences

• Detection Range:

  • hsCRP: Can detect concentrations accurately down to 0.3 mg/L 1
  • Standard CRP: Lower reporting level typically 3 mg/L 1

• Clinical Application:

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

• Standardization:

  • Both are typically calibrated to WHO 1st International Standard 85/506 or Certified Reference Material 470 (CRM 470) 1
  • Standardization efforts are ongoing to improve consistency among hsCRP assays 1

Clinical Interpretation

Risk Stratification

• hsCRP levels can be categorized into cardiovascular risk groups:
  • Low risk: <1.0 mg/L
  • Average risk: 1.0-3.0 mg/L
  • High risk: >3.0 mg/L 1

Clinical Utility

• hsCRP is recommended for cardiovascular risk assessment in patients with moderate risk profiles 1
• Standard CRP is more appropriate for diagnosing and monitoring acute inflammatory conditions 1

Analytical Considerations

• Recent studies show that modern standard CRP assays have become increasingly sensitive, with some having detection limits approaching those of hsCRP assays 2
• A 2022 study found 91.4% agreement between CRP and hsCRP measurements with an average difference of only 0.19 mg/L 2
• The correlation between standard CRP and hsCRP is very strong (Spearman regression R² = 0.98) 2

Practical Implications

• For cardiovascular risk assessment:

  • Use hsCRP for evaluating low-grade inflammation in apparently healthy individuals 1
  • Obtain two measurements (optimally 2 weeks apart) to determine baseline levels
  • Wait until resolution of any acute inflammatory stimulus (at least 2-3 weeks) before testing for cardiovascular risk assessment

• For diagnosing acute inflammation:

  • Standard CRP is sufficient and more cost-effective 1

Common Pitfalls

• Factors affecting CRP levels that should be considered when interpreting results:

  • Age, sex, BMI, smoking status
  • Exercise, diet, sleep patterns
  • Medications (particularly statins and anti-inflammatory drugs)
  • Underlying conditions like rheumatoid arthritis or inflammatory bowel disease

• Misclassification risk:

  • About 8% of patients may be misclassified when using standard CRP instead of hsCRP for cardiovascular risk assessment 2
  • This risk can be reduced by adjusting cutoff values slightly (e.g., lowering the moderate risk lower threshold from 1.0 to 0.9 mg/L) 3

In conclusion, while hsCRP was developed specifically to measure the lower concentrations relevant for cardiovascular risk assessment, recent advances in standard CRP assays have narrowed the technical gap between the two. For acute inflammation detection, standard CRP remains appropriate, while hsCRP is preferred for cardiovascular risk stratification, though some modern standard CRP assays may be suitable alternatives.