1. QuantiFERON® Blood Test for the Detection of
Latent Tuberculosis Infection

2. Active and Latent Tuberculosis Infection
TB-related morbidity and mortality
The TB pandemic – global emergency (1)
Active TB disease in 2013
9 million people developed TB disease
1.5 million people died
Latent TB infection (LTBI) in 2013
2 billion infected with M. tuberculosis
10% chance of developing active, contagious TB disease in their lifetimes
Screening and treatment (2)
2014 WHO guidelines, part of Broad strategy to “End TB” by 2035:
Identify and treat LTBI for upper-middle and high income countries with TB incidence <100/100k population
Screen and treat for LTBI in most at-risk populations for progression to active TB
Reduce TB deaths by 95%; cut active TB cases by 90%
As active TB rates decrease, LTBI diagnosis & preventive treatment grows in importance
1. WHO. Global tuberculosis report Dec 1, WHO. Guidelines on the management of latent tuberculosis infection Dec 1, 2014.
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3. Outcomes of Transmission of TB Infection
TB infection and disease can re-occur, even after treatment. This can happen as a result of the patient contracting a different strain or because bacteria remain that the individual’s immune system can’t keep under control. If the individual assumes an unhealthy lifestyle or becomes immunocompromised, the bacteria can potentially progress to disease again.
Outcomes depend on immune status and represent a spectrum of TB infection
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4. Why is it important to detect LTBI?
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5. Is it efficient enough to only consider active TB?
Ultimate goal of WHO is to eradicate active TB by 2050
This will not be achievable if only the active TB cases are considered
WHO Global Tuberculosis 2016 Report clearly states that treatment of LTBI is key for prevention of new infections
Adapted from Abu-Raddad et al. Epidemiological benefits of more-effective tuberculosis vaccines, drugs, and diagnostics. PNAS. 2009; 106;
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6. From Latent TB infection to Active TB: Risk Factors
Risk factors to develop active TB form Latent TB infection
Risk Factors
Estimation of relative risk*
AIDS
Well controlled HIV infection
Solid Organ Transplantation
Chronic Hemodialysis
Head and neck cancer 16
Recent tuberculosis infection (<2 years) 15
Systemic prolonged corticosteroids therapy
4.9
Anti-TNF  treatment
Diabetes
Malnutrition (body mass index < 20 kg/m2)
2 - 3
Passive smoking
* Compared to a population without any risk factor
HIV: Human Immunodeficiency Virus
TNF: Tumor Necrosis Factor
Leroy H. et al in La revue du praticien vol. 62, avril 2012 p 484, adapted from Landry J, Menzies D. Preventive chemotherapy. Where has it got us? Where to go next? Int J Tuberc Lung Dis 2008;12:
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7. How to diagnose LTBI?
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8. Principle of immunological tests (IGRA and TST)
Immune response: from latent to active Tuberculosis
Active TB
Latent TB Infection
Cell Mediated Immunity
Immune Response
Mycobacterial Load
Antibody
Infection
Active Disease
TIME
T0 (0 to 3 weeks) T3
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9. How to diagnose Latent TB Infection?
Principle of the immune reaction
Sources:
Andersen P et al, Lancet 2000
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10. Specificity of QuantiFERON versus TST
Mycobacterium tuberculosis complex
ESAT-6
CFP-10
IDR
Environmental Mycobacteria
M. tuberculosis +
M. Abcessus -
M. africanum
M. avium
M. bovis
M. branderi
M. celatum
BCG strains
M. chelonae
Gothenberg
M. fortuitum
Moreau
M. gordonii
Tice
M. intracellulare
Tokyo
M. kansasii
Danish
M. malmoense
Glaxo
M. marinum
Montréal
M. oenavense
Pasteur
M. scrofulaceum
M. smegmatis
M. szulgai
M. terra
M. vaccae
M. xenopi

11. Sampling tubes of QuantiFERON TB Gold Plus
NIL Tube
Negative control
Allows adjustment for background noise.
TB1 ANTIGEN Tube
Includes Mycobacterium tuberculosis specific antigens ESAT-6 and CFP-10
Peptides recognized by MHC Class II to detect CD4 response.
TB2 ANTIGEN Tube
Peptides recognized by MHC Class I and II to detect CD4 and CD8 combined response.
Mitogen Tube
Positive control
Includes PHA and allows to check the functionality of the immune system
Objectives:
To identify individuals with weakened immune system
To validate specimen handling conditions
Internal Training Use Only - January 2017

12. QuantiFERON-TB Gold Plus Protocol
Step 1: Whole Blood incubation
IFN- is stable at 2-8°C for at least 4 weeks
Nil
Control
ESAT-6
CFP-10
Mitogen
Control
2) 15 minutes Centrifugation
1) 1mL of whole blood (x4) and incubation at +37ºC for h.
Step 2: INF- ELISA testing
3) Add plasma and conjugate.
Incubation 2H at room temperature
4) Wash then add Substrate. OD reading after 30 min.
5) Calculation and results printing
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13. Results: Cut-off at 0.35 IU/mL
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14. Results interpretation
Interpretation of QuantiFERON results for LTBI screening
Negative QFT
Latent TB infection very unlikely
A negative result allows to eliminate LTBI with a probability close to 100% (NPV of 99.7%*)
Positive QFT
Latent TB infection very likely
In addition to clinical examination and anamnesis, a positive result allows to orient diagnosis toward a recent or old Latent TB infection (Specificity of 99.2%*)
An indeterminate QFT result means that the patient’s immune system is weakened (immunocompromised). This kind of result is very informative and must orient toward a specific patient management. An indeterminate result can also be the consequence of sample mishandling which need to be verify before interpretation.
Internal Training Use Only - January 2017

15. Benefits of QuantiFERON versus TST
Advantages of QuantiFERON
Antigens used in the test
Tuberculin: more than 200 antigens
ESAT6, CFP10
Specific to M. tuberculosis
No cross-reactivity with BCG
Patient Management
Day 1: Injection Day 3: Reading
Only one sampling
Only one visit
No loss of patients
Type de test
In vivo testing Operator dependent
In vitro testing
Single blood sampling Standardized reading Quality controls included
No booster effect
Reproducibility
Accuracy
Possible automation
Controls
None
Internal negative and positive controls ( Nil, Mitogen)
QFT Control Panel
Avoid false negative results
Certify the quality of the results
Positive threshold
Different thresholds
Unique threshold defined at 0.35 IU/mL
Better precision
Specificity of 99.2%
Sources:
1 – Diel et al, Performance of IGRAs and the TST: A new and up-to-date Meta-Analysis, Chest – Cheallaigh 2013
3 – Hsia 2012
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16. Which medical reasons remain for still using TST ?
Internal Training Use Only - January 2017