Causes of Elevated Procalcitonin
Procalcitonin (PCT) is primarily elevated in bacterial infections, with levels typically correlating with infection severity, ranging from 0.6-2.0 ng/mL for systemic inflammatory response syndrome, 2-10 ng/mL for severe sepsis, and >10 ng/mL for septic shock. 1
Common Causes of Elevated Procalcitonin
Infectious Causes
- Bacterial infections (primary cause)
- Sepsis and septic shock (highest elevations, often >10 ng/mL)
- Severe localized bacterial infections (moderate elevations)
- Bacterial pneumonia
- Bacterial meningitis
- Urinary tract infections with renal involvement
Non-Infectious Causes
- Major trauma (elevation in first 24-48 hours) 1, 2
- Burns (especially severe burns) 3, 2
- Major surgery (transient elevation post-operatively) 1, 2
- Certain malignancies:
- Treatment with drugs that stimulate pro-inflammatory cytokines 1
Viral Infections
- Severe viral illnesses like influenza and COVID-19 can cause PCT elevation, though typically to a lesser degree than bacterial infections 1
Diagnostic Value by PCT Level
| PCT Level | Clinical Interpretation |
|---|---|
| <0.05 ng/mL | Normal value in healthy individuals [1] |
| <0.25 ng/mL | Low probability of bacterial infection [1] |
| 0.25-0.5 ng/mL | Possible localized bacterial infection |
| 0.5-2.0 ng/mL | Systemic inflammatory response, possible early sepsis |
| 2.0-10 ng/mL | Severe sepsis likely [1] |
| >10 ng/mL | Septic shock, high mortality risk [1] |
Procalcitonin in Special Populations
Burn Patients
- PCT levels are elevated slightly at admission (mean 2.1 ng/mL) in burn patients 3
- Electrical burns may cause higher initial elevations (mean 15.7 ng/mL) 3
- Peak PCT levels correlate well with sepsis scoring in burn patients (r = 0.84) 3
- PCT levels >3 ng/mL in burn patients reliably indicate severe bacterial or fungal infection 3
- Values >10 ng/mL that continue to increase suggest life-threatening systemic infections 3
Gram-Negative vs. Gram-Positive Bacterial Infections
- PCT levels are significantly higher in Gram-negative bacterial sepsis compared to Gram-positive sepsis 4
- Highest elevations are seen with non-fermentative Gram-negative bacteria, Klebsiella pneumoniae, and other Enterobacteriaceae 4
Clinical Pearls and Pitfalls
- Important pitfall: PCT can be elevated in non-infectious conditions, particularly in the first 24-48 hours after major trauma, burns, or surgery 1, 2
- Key consideration: The individual trend of PCT values in a patient is more important than absolute values 3
- Clinical application: PCT can help guide antibiotic therapy decisions, with levels <0.25 ng/mL or decreasing by ≥80% from peak supporting antibiotic discontinuation in stabilized patients 1
- Limitation: PCT alone should not be used to make clinical decisions; it must be interpreted in conjunction with clinical assessment and other laboratory findings 1
PCT has superior diagnostic accuracy compared to other inflammatory markers like CRP for bacterial infections, with an area under the curve of 0.85 for diagnosing sepsis, sensitivity of 80%, and specificity of 77% 1.