it is a screening test so it must be used with other clinical judgement during therapeutic decisions

1. QuantiFERON-TB Gold
Medical Laboratory Scientist
Decca College Of Health And Allied Science
Ayoub Julai Nyanje

2. • QuantiFERON-TB Gold (QFT) is a simple blood test that aids in the
detection of Mycobacterium tuberculosis, the bacteria which causes
tuberculosis (TB).
• QFT is an interferon-gamma (IFN-γ) release assay, commonly known
as an IGRA, and is a modern alternative to the tuberculin skin test
Tuberculin skin tests (TST), Purified protein derivative PPD or
Mantoux). Unlike the TST,
• QFT is a controlled laboratory test that requires only one patient visit
and is unaffected by previous Bacille Calmette-Guerin (BCG)
vaccination.

3. • QFT is highly specific and sensitive: a positive result is strongly
predictive of true infection with M. tuberculosis. However, like the TST
and other IGRAs,
• QFT cannot distinguish between active tuberculosis disease and
latent tuberculosis infection, and is intended for use with risk
assessment, radiography, and other medical and diagnostic
evaluations. Like any diagnostic aid, QFT cannot replace clinical
judgment.

4. • The US Centers for Disease Control (CDC) Guidelines recommend the
use of IGRAs in all situations in which the TST was historically used,
with Interferon-Gamma Release Assays (IGRAs), being the preferred
test for persons who have been BCG vaccinated or are unlikely to
return for TST reading.

5. The QFT advantage – three tubes, one clear result
QFT uses unique blood
collection tubes that enable
immediate exposure of viable
blood lymphocytes to highly
specific TB antigens (ESAT-
6/CFP-10/TB-7.7(p4)) and test
controls coated on the inner
surface of the tubes. Antigen
exposure produces a quantifiable
immune response to aid in the
diagnosis of TB infection.

6. • Nil tube
Negative control to adjust for background IFN-γ
• TB Antigen tube
To detect the CD4+ T cell responses to TB antigens
• Mitogen tube
Low response may indicate inability to generate IFN-γ

7. QFT is the most clinically tested and proven IGRA.
• QuantiFERON-TB Gold is the most clinically tested and proven IGRA
available.More than 30 million QFT tests have been sold across 130+
countries, including more than 7 million in 2015. Trust the only blood
test for TB infection that offers
• The most accurate and reproducible results for TB infection
• The confidence of more than 1200 clinical and scientific studies
• Convenient and objective ELISA technology
• Single visit testing

8. QFT has simple blood collection and convenient
workflow
• QFT employs whole blood collection to make T cell incubation simple
and fast. After blood collection, the sample must be incubated, which
can occur on-site or at the testing laboratory, providing your practice
with complete flexibility and convenience.

10. Benefits of the QuantiFERON technology
• Use of whole blood in QFT makes T cell incubation simple and fast,
and reduces labor
• No tedious lymphocyte isolation, washing, counting, diluting, or
culturing
• Technology designed for clinical screening of large sample numbers,
providing the standards, controls, and assay reproducibility needed
for clinical diagnosis

11. SD BIOSENSOR F2400

12. Specimen collection
i. Collect more than 3.5ml (Venous blood) in a heparin tube .
ii. After blood collection it should be stored at room temperature
iii. Within 16 hours after collection dispense 1ml into each TB-feron
with micro pipette
iv. as soon as tube is filled with blood, shake it 10times gently or use a
Roller- rocker to allow the entire surface of the tube to be immersed
in blood so that blood and antigen on tube wall can be mixed well

13. Standard operating procedure for performing
QuantiFERON-TB
Procedure
1. Collect blood in well labeled green top tube with Lithium
2. Pipette 1ml (1000ul) of blood to red top tube ,purple top tube and
grey top tube.
3. Mix (10 times) or by using roller for 5minutes
4. Incubate for 16-24hrs at 37oC
5. Centrifuge for 4500 RPM for 15min
6. Switch on machine SD-Bionsor
7. Select Patient ID following adding patient name then place start

14. Steps cont…
8. Bring the test devices and Tablets pellets to room temperature since
they stored in refrigerator (2-8oC
9.Pippete 100ul of sample (plasma) into tube with tablets pellets gently
mixing to avoid formation of bubbles
10. The machine will instruct the user to insert the test device with
barcode point upward ,the machine will scan the device to ensure
validity and then test will partially ejected leaving the sample well
opened
11. First tube with gray top will be displayed ,the mixture off pellets
from step 9 will be pipetted and poured into sample well then click
start , repeat procedure from step 9 to 11 for the next tubes

15. • 11. wait for the results (15 minutes )
• Reporting of results
i. Negative
ii. Positive
iii. In determinant (with comment report sample collection after 2
weeks)

16. NOTE
• Plasma samples should only be harvested using a pipet.
• After centrifugation, avoid pipetting up and down or mixing plasma by
any means prior to harvesting. At all times, take care not to disturb
material on the surface of the gel
• Plasma samples can be loaded directly from centrifuged blood
collection tubes into the QFT ELISA plate, including when automated
ELISA workstations are used.
• Plasma samples can be stored for up to 28 days at 2°C to 8°C or, if
harvested, below –20°C for extended periods
• For adequate test samples, harvest at least 150 µl of plasma.

17. Source of errors to patient results
• Fail to follow standard operating procedure
• Incompetence of the personnel
• Poor specimen collection technique
• Incubation of three tubes at wrong temperature
• Using expired kit devices
• Poor storage of three tube

18. Reference
• https://www.quantiferon.com/products/quantiferon-tb-gold/
• Centers for Disease Control and Prevention. (2010) Updated
guidelines for using interferon-gamma release assays to detect
Mycobacterium tuberculosis infection — United States. MMWR
59(RR05), 1.