What inflammatory biomarkers (high‑sensitivity C‑reactive protein, erythrocyte sedimentation rate, interleukin‑6, tumor necrosis factor‑α, antinuclear antibody, rheumatoid factor) should be ordered to assess inflammation?

Checking Inflammatory Biomarkers

High-sensitivity C-reactive protein (hs-CRP) is the only inflammatory biomarker that should be routinely ordered to assess inflammation, as it has the best evidence for standardization, clinical utility, and predictive value. 1

Primary Recommendation: hs-CRP Only

The CDC/AHA consensus guidelines explicitly identify hs-CRP as the analyte of choice after systematic evaluation of stability, assay precision, accuracy, availability, and standardization 1. The measurement of alternative or additional inflammatory markers beyond hs-CRP is not recommended at this time 1.

Why hs-CRP is Superior

From a clinical chemistry perspective, hs-CRP outperforms all other inflammatory markers because:

• It has acceptable precision down to 0.3 mg/L
• Standardized assays are widely available with proficiency testing programs
• The analyte remains stable (unlike cytokines which require freezing)
• Population norms are well-established across 40,000 persons from 15 populations 1

Other Markers: Not Recommended for Routine Use

ESR (Erythrocyte Sedimentation Rate):

• Should not be ordered routinely alongside hs-CRP
• Age is the primary determinant of ESR elevation in healthy populations, not inflammation 2
• Discordance between ESR and CRP is common and creates clinical confusion 3

IL-6 (Interleukin-6):

• No standardized commercial assays available for clinical use 1
• Requires frozen samples, limiting use to research settings 1
• While IL-6 correlates with disease activity in specific conditions like rheumatoid arthritis 4, 5, it lacks the standardization needed for routine clinical practice

TNF-α (Tumor Necrosis Factor-α):

• Does not correlate with treatment response or disease activity 4
• No clinical utility as a biomarker despite its pathophysiological role 6

ANA (Antinuclear Antibody) and RF (Rheumatoid Factor):

• These are autoantibodies, not inflammatory markers
• Used for diagnosis of specific autoimmune diseases (SLE, RA), not for assessing inflammation 7, 8
• Should only be ordered when there is clinical suspicion of autoimmune disease

How to Measure hs-CRP Correctly

When you do order hs-CRP:

1. Timing: Measure in metabolically stable patients without active infection or obvious inflammation 1
2. Repeat testing: Average two measurements taken 2 weeks apart for stable estimates 1
3. Fasting status: Not required 1
4. Units: Report only as mg/L 1
5. If ≥10 mg/L: Discard result, search for infection/inflammation, remeasure in 2 weeks 1

Risk Stratification Cutpoints

• Low risk: <1.0 mg/L
• Average risk: 1.0-3.0 mg/L
• High risk: >3.0 mg/L 1

These correspond to population tertiles with 2-fold increased relative risk in the high-risk category 1.

Clinical Context for Ordering

Best use: Patients at intermediate cardiovascular risk (10-20% 10-year CHD risk) where additional risk stratification would change management decisions regarding further testing or therapy 1.

Poor use: Routine screening in all patients or those already at high risk (>20% 10-year risk) who warrant aggressive treatment regardless 1.

Common Pitfalls

• Ordering multiple inflammatory markers simultaneously: This creates confusion from discordant results without improving clinical decision-making
• Using ESR instead of hs-CRP: ESR is primarily age-dependent in healthy populations and less specific for inflammation 2
• Ordering IL-6 or TNF-α clinically: These lack standardized assays and clinical utility outside research settings 1, 4
• Confusing autoantibodies (ANA, RF) with inflammatory markers: These serve entirely different diagnostic purposes

The evidence strongly supports a simplified approach: order hs-CRP alone when inflammatory assessment is needed, measured correctly with two samples averaged 2 weeks apart 1.