This document discusses the Quantiferon Gold test for detecting latent tuberculosis infection. It provides background on the incidence of TB and risk of progression to active disease. It then explains the mechanism of the QFG test, which uses antigens to stimulate a type 4 hypersensitivity reaction. While not proven superior to the TST, it can be useful for evaluating children exposed or from high incidence areas. Guidelines recommend its use for young children and those with close contact or immune suppression.

1. Quantiferon Gold
03.08.2018
Ahikam DJ

2. Rationale: Latent TB
• Incidence of TB: 14.4-43/100,000 in London
• 5% are <15 years
• 30% of those exposed get LTBI
• Of which 5-10% get disease
• In infants, risk of progression to pulmonary TB
is 30-40%; meningeal/miliary TB is 10-20%
• Treatment of LTBI reduces risk by 60% or more

3. https://www.google.co.in/url?sa=i&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwjr3N3a6s7cAhXGMo8KHfomD8YQjRx6BAgBEAU&url=https%3A%2F%2Fww
w.e7health.com%2Fcorporate-tb-skin-testing%2F&psig=AOvVaw2IdRMnsCqKcvoIAj2l56Lz&ust=1533314557033111

4. QFG: Mechanism
• In-vitro type 4 hypersensitivity reaction
• Antigens:
– ESAT-6: Early-secretory protein 6
– CFP-10: Culture-filtrate protein 10
– TB 7.7

5. QFG: Procedure
https://education.questdiagnostics.com/presentations/igras-in-the-diagnosis-of-tuberculosis?presentation_id=101

6. TST Vs IGRA
• In vivo
• 2- visit test
• Cheap
• In vitro
• BCG vaccination does
not produce false
positive

7. The Evidence
• Not much to prove superiority over TST in
specificity or sensitivity
• Glitch being non-availability of gold standard
to dectect LTBI
• Useful adjunct to evaluate children suspected
with TB
• Neither sensitive nor specific enought to rule
out or confirm TB

8. NICE Guidelines
• For those in close contact of TB
– Neonate
– <5 years
– >5 years
• Child from area of incidence greater than
40/100,000
• Child with immune suppression

9. Reference
• How to use: interferon γ release assay for
tuberculosis
Pollock et al. Arch Dis Child Educ Pract Ed 2013 98:99-105