What are the best blood tests to measure inflammation?

Best Blood Tests for Measuring Inflammation

High-sensitivity C-reactive protein (hs-CRP) is the best blood test for measuring inflammation due to its standardization, precision, wide availability, and established clinical utility. 1

Primary Inflammatory Markers

hs-CRP (High-sensitivity C-reactive protein)

• Most reliable and clinically useful inflammatory marker with the following advantages:
  • Preanalytical stability in serum or plasma at room temperature or frozen for extended periods 1
  • Commercial automated assays widely available with acceptable precision down to 0.3 mg/L 1
  • Standardized testing with proficiency programs from the College of American Pathologists 1
  • Clear clinical correlation with inflammatory conditions and cardiovascular risk 1
  • Rapid response to acute inflammation (rises within hours) 2

ESR (Erythrocyte Sedimentation Rate)

• Indirect measure of inflammation with longer half-life than CRP 2
• Better for monitoring chronic inflammatory conditions 2
• Limitations:
  • Affected by non-inflammatory factors (age, gender, anemia, pregnancy) 3
  • Slower to respond to changes in inflammatory activity 4
  • Less specific than CRP 3

Combined CRP and ESR Interpretation

CRP	ESR	Interpretation
Elevated	Normal	Acute inflammation [5]
Normal	Elevated	Chronic inflammation or non-inflammatory factors [5]
Elevated	Elevated	Active inflammation [5]
Normal	Normal	Low likelihood of significant inflammation [5]

Secondary Inflammatory Markers

Fibrinogen

• Acute-phase reactant produced by the liver 1
• Limitations:
  • Stability issues if not analyzed immediately (for clotting-based assays) 1
  • Different methodologies make standardization problematic 1
  • Less suitable for routine clinical use compared to CRP 1

Serum Amyloid A (SAA)

• Acute-phase reactant with limited commercial availability 1
• Currently available primarily for research use 1
• Standardization issues due to multiple SAA phenotypes 1

White Blood Cell (WBC) Count

• Simple, widely available test 1
• Less specific for inflammation than CRP 1
• Useful as part of initial inflammatory assessment 5

Fecal Calprotectin

• Highly specific for intestinal inflammation 5
• Particularly useful for inflammatory bowel disease 5
• Interpretation:
  • <50 mg/g: High sensitivity (88%) for ruling out inflammation 5

  • 250 mg/g: Higher specificity (74%) for active inflammation 5

Clinical Application Algorithm

1. Initial Assessment of Inflammation:

   • Order hs-CRP as the primary test for detecting inflammation 1
   • Add CBC with differential for broader assessment 5

2. For Chronic Inflammatory Conditions:

   • Include both hs-CRP and ESR to distinguish between acute and chronic inflammation 2
   • Consider disease-specific markers based on clinical suspicion 5

3. For Gastrointestinal Inflammation:

   • Add fecal calprotectin to assess intestinal inflammation 5

4. For Monitoring Treatment Response:

   • Use hs-CRP for acute conditions due to its rapid response 2
   • Use ESR for chronic conditions due to its slower kinetics 2

Common Pitfalls to Avoid

• Ordering both CRP and ESR routinely is unnecessary and wasteful in most cases 6
• Interpreting inflammatory markers without clinical context can lead to diagnostic errors 3
• Failing to recognize that some conditions may not elevate inflammatory markers despite active disease 3
• Not accounting for factors that can falsely elevate ESR (anemia, pregnancy, older age) 3
• Overlooking that CRP can be elevated in non-infectious conditions like tissue injury 4

By selecting the appropriate inflammatory marker based on the clinical scenario and interpreting results in context with the patient's presentation, clinicians can optimize the diagnostic and monitoring value of these tests while minimizing unnecessary testing.