Inflammation
C-reactive proteinCRP / hs-CRP
Acute-phase reactant; high-sensitivity assay refines cardiovascular risk in low values.
Sample
Serum
Clinical reference range
— to 8 mg/L
Standard CRP
Conv: —–8 mg/LFunc: —–1 mg/L
Biology
What it measures
Hepatic pentamer induced by IL-6. Half-life ~19 h. Binds phosphocholine on apoptotic cells and pathogens.
Clinical use
Why we order it
Detect/monitor infection and inflammation; hs-CRP refines ASCVD risk (<1 low, 1–3 average, >3 high).
Lens · Clinical
Interpretation by lens
Clinical interpretation
AHA: average two hs-CRP values 2 weeks apart; >10 indicates non-CV cause.
Differential
Causes of abnormal values
Causes of HIGH
- ↑Bacterial infection (>50 mg/L common; >100 favors bacterial over viral)
- ↑Autoimmune disease flare
- ↑Tissue injury / surgery
- ↑Obesity / metabolic syndrome
- ↑Smoking
Causes of LOW
- ↓No clinical low
Pitfalls
Pre-analytic & interpretation traps
- !A single hs-CRP can be transiently elevated by minor infection; repeat in 2–3 weeks for risk stratification.
- !CRP is induced by IL-6 — anti-IL6 therapies (tocilizumab) suppress CRP regardless of infection.
Evidence-graded claims
What the data says
B
hs-CRP refines CV risk stratification (JUPITER population)
Useful especially in intermediate-risk patients.
B
CRP-guided antibiotic stewardship reduces unnecessary prescribing in primary care
Cochrane review supports modest reduction.
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