Procalcitonin Level Test
Procalcitonin Test (PCT)
Key Points
- Biomarker for bacterial infection and sepsis
- Higher specificity than CRP and ESR
- Rapid response to bacterial infections
- Valuable tool in antibiotic stewardship
- Particularly useful in pediatric emergency settings
Biochemistry
Procalcitonin is a 116-amino acid peptide precursor of calcitonin, produced by:
- Thyroid C cells (under normal conditions)
- Various extrathyroid tissues (during bacterial infection)
- Significantly upregulated by bacterial endotoxins and inflammatory cytokines
- Minimal elevation in viral infections
Primary Clinical Indications
- Early Sepsis Detection
- Neonatal sepsis evaluation
- Late-onset sepsis in NICU
- Pediatric intensive care settings
- Post-operative infection monitoring
- Respiratory Tract Infections
- Community-acquired pneumonia
- Bronchiolitis differentiation
- Ventilator-associated pneumonia
- Specific Pediatric Conditions
- Febrile neutropenia assessment
- Meningitis evaluation
- Urinary tract infections
- Acute appendicitis
Advantages in Pediatric Practice
- Early marker (increases within 2-4 hours of infection)
- High negative predictive value
- Helps distinguish bacterial from viral infections
- Guides antibiotic therapy decisions
- Monitors treatment response
Testing Methods
Sample Collection
- Specimen Type:
- Serum (preferred)
- Plasma (EDTA or heparin)
- Required volume: 0.5-1.0 mL
- Collection Timing:
- Before antibiotic administration (ideal)
- Serial measurements every 24-48 hours for monitoring
Analytical Methods
- Immunoassay Techniques
- ELISA (enzyme-linked immunosorbent assay)
- ECLIA (electrochemiluminescence immunoassay)
- TRACE (time-resolved amplified cryptate emission)
- Point-of-care testing systems
- Quality Control
- Internal calibration standards
- External quality assessment
- Method-specific reference ranges
Result Interpretation
Reference Ranges
- Healthy newborns (0-48h): <10 ng/mL
- Healthy newborns (48-72h): <0.5 ng/mL
- Children and adults: <0.15 ng/mL
Clinical Decision Points
- <0.1 ng/mL: Bacterial infection very unlikely
- 0.1-0.5 ng/mL: Local bacterial infection possible
- 0.5-2.0 ng/mL: Systemic infection likely
- >2.0 ng/mL: High risk of severe sepsis/septic shock
- >10.0 ng/mL: Severe bacterial sepsis or septic shock
Kinetics
- Increase: Within 2-4 hours of infection
- Peak: 24-48 hours
- Half-life: 24-36 hours
- Normalization: 3-7 days with effective treatment
Confounding Factors
- False Positives
- Major trauma or surgery
- Severe burns
- Cardiogenic shock
- First 48 hours of life
- Some autoimmune conditions
- False Negatives
- Early course of infection
- Localized infections
- Subacute bacterial endocarditis
- Prior antibiotic use
Age-Specific Considerations
- Neonatal Period
- Physiologic elevation in first 48 hours
- Different cutoff values needed
- Serial measurements more valuable
- Chronic Conditions
- Renal impairment affects levels
- Immunocompromised states
- Oncology patients
Clinical Practice Guidelines
Antibiotic Stewardship
- Initial Prescription:
- Consider withholding antibiotics if PCT <0.25 ng/mL
- Strongly consider antibiotics if PCT >0.5 ng/mL
- Mandatory antibiotics if PCT >2.0 ng/mL
- Treatment Duration:
- Consider discontinuation when PCT decreases by 80%
- Or when PCT <0.25 ng/mL
- Serial measurements every 24-48 hours
Cost-Effectiveness
- Benefits:
- Reduced antibiotic exposure
- Shorter hospital stays
- Lower antimicrobial resistance
- Decreased healthcare costs
- Implementation Strategies:
- Protocol development
- Staff education
- Quality metrics monitoring
- Regular protocol updates
