Quantiferon-TB Gold Test
Quantiferon-TB Gold Test Kits
Introduction
An interferon-gamma release assay (IGRA) used to detect Mycobacterium tuberculosis infection by measuring the immune response to specific TB proteins in whole blood samples.
Test Components
- Collection Tubes:
- Nil Control (Grey cap)
- TB Antigen (Red cap)
- Mitogen Control (Purple cap)
- Optional: TB7.7 Antigen (Yellow cap)
- Kit Contents:
- Blood collection tubes
- Package insert
- Tube labels
- Specimen transport bags
Clinical Applications
- Primary Uses:
- Latent TB infection screening
- Active TB disease assessment
- Contact investigations
- Healthcare worker screening
- Immigration screening
- Advantages in Pediatrics:
- Single patient visit
- No return for reading
- Unaffected by BCG vaccination
- Higher specificity than TST
Specimen Collection
- Collection Protocol:
- 1mL blood per tube
- Proper tube order
- Immediate mixing (10 times)
- Temperature control (17-25°C)
- Critical Steps:
- Proper patient identification
- Aseptic technique
- Accurate volume collection
- Proper tube labeling
- Transport timing considerations
Processing Requirements
- Time Constraints:
- Incubation within 16 hours
- 37°C ± 1°C incubation
- 16-24 hour incubation period
- Centrifugation parameters
- Storage Conditions:
- Room temperature transport
- No refrigeration
- Avoid extreme temperatures
- Plasma storage requirements
Result Interpretation
- Calculation:
- TB Antigen minus Nil
- Mitogen minus Nil
- Cut-off values
- Quality control criteria
- Result Categories:
- Positive: ≥0.35 IU/mL
- Negative: <0.35 IU/mL
- Indeterminate results
- Invalid results
Clinical Considerations
- Special Populations:
- Immunocompromised patients
- Infants and young children
- Recent TB contacts
- Healthcare workers
- Limitations:
- Cost considerations
- Laboratory accessibility
- Processing time constraints
- Age limitations
Quality Assurance
- Pre-analytical:
- Proper storage of tubes
- Collection technique
- Transport conditions
- Documentation accuracy
- Analytical:
- Internal controls
- Temperature monitoring
- Incubation timing
- Equipment calibration
Documentation Requirements
- Collection date and time
- Collector identification
- Transport conditions
- Processing parameters
- Result interpretation
- Clinical correlation
