QuantiFERON-TB Gold (QFT) Kit

For use as an indirect test for Mycobacterium tuberculosis (TB) infection (1)

Features

  • Accurate and unaffected by prior BCG vaccination (2–4)
  • Efficient, with results after one patient visit (1)
  • Objective results (1)

Product Details

QuantiFERON-TB Gold is an in vitro diagnotic test that aids in the detection of M. tuberculosis infection. QFT is an interferon γ (IFNγ) release assay (IGRA) which measures the cell-mediated response to specific TB antigens in whole blood.

Performance

Tuberculosis (TB) remains a significant threat to humanity, and therefore identifying TB infection is essential. A person infected with Mycobacterium tuberculosis, but who shows no symptoms, is regarded as having latent TB infection. Global organizations acknowledge that to fight TB effectively, accurate identification and treatment of latent TB infection, as well as active TB disease, are vital (5).

QuantiFERON-TB Gold (QFT) is a modern alternative to the 110 year old tuberculin skin test (or Mantoux test) and is the most studied IGRA, with over 800 published peer-reviewed publications. The test is highly accurate and unaffected by Bacillus Calmette-Guérin (BCG) vaccination (2–4).

QFT is an interferon-gamma (IFNγ) release assay, commonly known as an IGRA, and measures the cell-mediated immune response to specific TB antigens in whole blood. Patients may be tested in a single patient visit, with objective results, eliminating the need for two-step testing (1).

By reducing false positive results seen with TST, QFT reduces the costs associated with labor costs resulting from two-step TST testing. Studies show that QFT can reduce the cost of maintaining healthcare worker screening programs by up to 32% (6).

Principle

QFT uses a peptide cocktail simulating ESAT-6, CFP-10, and TB7.7(p4) proteins to stimulate cells in heparinized whole blood. Detection of IFNγ by ELISA is used to identify in vitro responses to these peptide antigens, which are associated with M. tuberculosis infection (Table 1 and figure QuantiFERON-TB Gold interpretation flowchart).
Table 1. QuantiFERON-TB Gold test results
QFT result Likelihood of TB infection
Positive Likely
Negative Not likely
Indeterminate Results are indeterminate for TB antigen responsiveness 
 

When a TB infection can neither be excluded nor confirmed (Indeterminate QFT result), further evaluations are required. Table adapted from: QFT Package Insert (1).

Procedure

The QFT assay is a straightforward laboratory test that involves the following steps:

1. Collect whole blood in specialized QFT blood collection tubes.
2. Incubate for 16 to 24 hours at 37°C.
3. Detect released IFNγ in harvested plasma by ELISA.
4. Analyze results using QFT Analysis Software or manually. 

QFT has 3 blood collection tubes (Nil, TB Antigen, and Mitogen) — 1 ml of whole blood should be collected into each tube.

Applications

QFT can be used in many clinical and public health settings, including screening for healthcare workers, immigrants, military personnel, those in correctional facilities, homeless individuals, and people in at-risk populations.

Supporting data and figures