Mantoux Test (Tuberculin Skin Test)
Key Points
- Gold standard for TB infection screening in children
- Uses purified protein derivative (PPD)
- Reading window: 48-72 hours
- Interpretation varies by risk factors
- False positives and negatives are possible
Immunological Basis
- Type IV delayed hypersensitivity reaction
- Measures cellular immune response to TB antigens
- Development of induration through:
- T-lymphocyte recruitment
- Cytokine release
- Local inflammatory response
- Fibrin deposition
Administration Technique
Pre-procedure Requirements
- Storage conditions:
- Temperature: 2-8°C
- Protected from light
- No freezing
- Equipment needed:
- 27-gauge needle
- 1mL tuberculin syringe
- PPD solution (5 TU/0.1mL)
- Alcohol swabs
- Gloves
Step-by-Step Procedure
- Site selection:
- Volar aspect of forearm
- 2-4 inches below elbow joint
- Away from veins or lesions
- Injection technique:
- Clean site with alcohol
- Allow to dry completely
- Stretch skin slightly
- Insert needle at 5-15° angle
- Inject 0.1mL intradermally
- Create 6-10mm wheal
- Do not cover with bandage
Result Interpretation
Measurement Technique
- Timing: 48-72 hours post-administration
- Measure induration, not erythema
- Use ballpoint pen method
- Measure transverse diameter in millimeters
Interpretation Criteria
- ≥5mm considered positive in:
- HIV-positive children
- Recent TB contacts
- Children with chest X-ray consistent with TB
- Immunosuppressed patients
- ≥10mm considered positive in:
- Children < 4 years old
- High-risk medical conditions
- Recent immigrants from high-prevalence countries
- Drug users
- ≥15mm considered positive in:
- Children ≥4 years without risk factors
- Low-risk populations
False Results
False Negatives
- Causes:
- Recent TB infection (< 8 weeks)
- Overwhelming TB disease
- Immunosuppression
- Live viral vaccines
- Malnutrition
- Neonatal age
- Technical errors
False Positives
- Causes:
- BCG vaccination
- Non-tuberculous mycobacterial infection
- Incorrect measurement technique
- Wrong interpretation of cutoff values
Clinical Applications
- Screening indications:
- Contact investigation
- Immigration screening
- Healthcare worker screening
- Pre-biological therapy
- Contraindications:
- Previous severe reaction
- Active TB disease
- Extensive burns/eczema
Special Considerations in Children
- Age-specific considerations:
- Higher false-negative rates in infants
- BCG influence varies by age at vaccination
- More reliable in older children
- Documentation requirements:
- Date and time of placement
- Lot number of PPD
- Site of placement
- Administrator's name
- Date and time of reading
- Result in millimeters
- Reader's name
Disclaimer
The notes provided on Pediatime are generated from online resources and AI sources and have been carefully checked for accuracy. However, these notes are not intended to replace standard textbooks. They are designed to serve as a quick review and revision tool for medical students and professionals, and to aid in theory exam preparation. For comprehensive learning, please refer to recommended textbooks and guidelines.
