QuantiFERON-TB Gold

What is QuantiFERON-TB Gold?

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-y ) release assay, commonly known as an IGRA, and is a modern alternative to the  tuberculin skin test (TST or Mantoux). Unlike the TST, QFT is a controlled laboratory test that requires only one patient visit and is unaffected by previous vaccination with Bacille-Calmette Guerin (BCG).

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 judgement.
 

How does it work?

QFT measures the cell-mediated immune response (cytokines) to very specific TB antigens. The test is performed by collecting whole blood (1 mL) into each of three blood collection tubes. When the blood of an infected patient is stimulated with the M. tuberculosis-specific antigens in QFT, their T-Cells respond by secreting a cytokine called IFN-y. The IFN-y concentration in the plasma is determined using a sensitive ELISA.

Why Use QFT?

QFT has well-established clinical utility and is the most clinically tested and proven IGRA. Rely on the only test that offers:

  • Objective and reproducible results
  • Convenient ELISA technology with objective analysis software
  • Greater than 900 clinical and scientific studies

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video about improving your TB screening by switching to QuantiFERON-TB Gold (QFT)

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The key to the eradication of TB is prevention

Tuberculosis (TB) continues to infect people in both developed and developing countries. At least two billion people are thought to be infected with Mycobacterium tuberculosis, a bacterium that is the primary cause of TB. Detection and treatment of active and latent TB infection (LTBI) are part of effective disease prevention (Figure 1).

TB Infections per million

Figure 1. Benefits of fighting active and latent TB (1).

The World Health Organization (WHO) acknowledges that to fight TB effectively, the accurate identification and treatment of latent TB infections, as well as active TB disease are vital (2).

Those at greatest risk should be prioritized for screening (3–9):

  • Healthcare workers (HCWs)
  • Military personnel
  • Elderly people
  • Students
  • Immigrants
  • Close contacts of persons known or suspected to have active TB
  • People who are residents in long-term care facilities
  • People with weakened immune systems
  • Prison inmates and persons living in other congregate settings

Why not choose the most clinically proven, modern testing solution?

QuantiFERON-TB Gold (QFT®) is a highly specific, controlled blood test to aid in the diagnosis of infection with M. tuberculosis. Known as an interferon-gamma release assay (IGRA), QFT provides the value of robust technology. QFT is the ideal solution for the accurate identification of TB infection that is needed for effective disease prevention.

The modern replacement for the tuberculin skin test

Tuberculous test
Figure 2. QuantiFERON-TB Gold blood collection tubes. (L to R) Nil tube (negative control), TB Antigen tube, and Mitogen tube (positive control). The TB Antigen tube assesses IFN-response to highly specific TB antigens. The Mitogen tube can be useful to indicate patient’s immune status and correct blood handling and incubation. The Nil tube adjusts for background IFN-.

Unlike the tuberculin skin test (TST), QFT is a controlled laboratory test that requires only one patient visit and is unaffected by previous vaccination with Bacille-Calmette Guerin (BCG) (4, 10, 11) (Table 1). QFT is a highly accurate, cost-effective testing solution. QFT has unique blood collection tubes (Figure 2), enabling immediate exposure of blood lymphocytes to highly-specific TB antigens and test controls coated on the inner surface of the tubes. The Nil tube (negative control) adjusts for background interferon gamma (IFN). The Mitogen tube serves as a positive control and can be useful for indicating correct sample handling and incubation, as well as a patient’s immune status.

The TB Antigen tube contains highly-specific TB antigens, ESAT-6/CFP-10/TB-7.7(p4).

Table 1. A modern test for TB infection — QuantiFERON-TB Gold
A modern test for TB infection — QuantiFERON-TB Gold

The US Centers for Disease Control (CDC) Guidelines recommend the use of IGRAs in all situations in which the TST was historically used, with IGRAs being the preferred test for persons who have been BCG vaccinated or are unlikely to return for TST reading (3).

QFT has well-established clinical utility and is the most clinically tested and proven IGRA (12).

Rely on the only LTBI test that offers:

  • Objective and reproducible results
  • Convenient ELISA technology with objective analysis software
  • Greater than 900 clinical and scientific studies

QFT provides a new paradigm in diagnosing TB infection

When compared with other IGRA products, which require subjective counting of spots, QuantiFERON-TB Gold provides quantitative detection with a user-friendly workflow (Tables 2 and 3).

Table 2. QuantiFERON-TB Gold vs. other IGRAs on the market
QuantiFERON-TB Gold vs. other IGRAs on the  market

*CPT tubes are not compatible with Xtend.

Table 3. Results of the largest prospective comparison of IGRAs (>2400 subjects), in a cohort of healthcare workers, commissioned by the CDC (20)
IGRA Results

Almost 9% of healthcare workers tested with ELISpot would require repeat testing:more than five times that of QFT.

QFT has simple blood collection and convenient workflow

The workflow for QFT, from blood collection to calculation of results, includes 4 easy steps (Figure 2).
http://www.quantiferon.com//IRM/ShowMedia.aspx?MediaId=8

Figure 2. Workflow from blood collection and sample assay setup to calculation of results, using ELISA technology and QFT analysis software.

Table 4. Interpretation criteria for QuantiFERON-TB Gold
Interpretation criteria for QuantiFERON-TB Gold

Note: A low-mitogen result, in conjunction with a negative TB result, is classified as an indeterminate result.

*Corrected for Nil response.

QFT is an indirect test for M. tuberculosis infection (including disease) and is intended for use in conjunction with risk assessment, radiography, and other medical and diagnostic evaluations.

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
  • Mix each tube and incubate overnight
  • QFT preserves the in vivo cellular and biochemical environment for lymphocyte stimulation, maximizing cellular responses
  • Technology designed for clinical screening of large sample numbers, providing the standards, controls, and assay reproducibility needed for clinical diagnosis

Choose the most clinically proven testing solution — QuantiFERON-TB Gold!

Valuable resources are available from the US Centers of Disease Control and Prevention (CDC) The CDC’s Division of Tuberculosis Elimination has funded five TB Regional Training and Medical Consultation Center (RTMCCs). These centers provide training, technical assistance, medical consultation, and the development of education materials to TB programs and healthcare providers (21). To learn more about the RTMCC that covers your region, visit www.cdc.gov/tb/education/rtmc/default.htm.

Who is at risk for TB?

  • Healthcare workers
  • Military personnel
  • Elderly people
  • Students
  • Immigrants
  • Close contacts of persons known or suspected  to have active TB
  • People who are residents in long-term care facilities
  • People with weakened immune systems
  • Prison inmates and persons living in other congregate settings

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References

1. Abu-Raddad, L.J. et al. Epidemiological benefits of more-effective tuberculosis vaccines, drugs, and diagnostics. Proc. Natl. Acad. Sci. U S A. 106,13980.

2. World Health Organization. (2013) Global tuberculosis report 2013. www.who.int.tb/publications/global_report/en.

3. 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.

4. QuantiFERON-TB Gold Package Insert. March 2013. US05990301L. US customers should consult current online version for their country at www.QuantiFERON.com.

5. Baussano, I., Nunn, P., Williams, B., Pivetta, E., Bugiani, M., Scano, F. (2011) Tuberculosis among health care workers. Emerg. Infect. Dis. 17, 488.

6. Cheallaigh, C.N. et al. (2013) Interferon gamma release assays for the diagnosis of latent TB infection in HIV-infected individuals in a low TB burden country. PLoS One 8(1), e53330.

7. Hoffmann, M., Tsinalis, D., Vernazza, P., Fierz, W., Binet, I. (2010) Assessment of an Interferon-gamma release assay for the diagnosis of latent tuberculosis infection in haemodialysis patient. Swiss Med.Wkly. 140, 286.

8. Kwakernaak, A.J., Houtman, P.M.,Weel, J.F., Spoorenberg, J.P., Jansen, T.L. (2011) A comparison of an interferon-gamma release assay and tuberculin skin test in refractory inflammatory disease patients screened for latent tuberculosis prior to the initiation of the first tumor necrosis factor -inhibitor. Clin. Rheumatol. 30, 505.

9. Pratt, A., Nicholl, K., Kay, L. (2007) Use of the QuantiFERON TB Gold test as part of a screening programme in patients with RA under consideration for treatment with anti-TNF-agents: the Newcastle (UK) experience. Rheutmatology (Oxford). 46, 1035.

10. Diel, R., Loddenkemper, R., Nienhaus, A. (2010) Evidence-based comparison of commercial interferon-gamma assays for detecting active TB: a metaanalysis. Chest 137, 952.

11. Harada, N. et al. (2008) Comparison of the sensitivity and specificity of two whole blood interferon-gamma assays for M. tuberculosis infection. J. Infect. 56, 348.

12. www.gnowee.net. The QuantiFERON reference library: (accessed June 26, 2014).

13. Tuberculin Purified Protein Derivative (Mantoux) TUBERSOL®. Package Insert. Sanofi Pasteur Limited. February 2013. R8-2013.

14. Ramos, J.M. et al. (2012) Contribution of interferon gamma release assays testing to the diagnosis of latent tuberculosis infection in HIV- infected patients: a comparison of QuantiFERON-TB Gold In Tube, T-SPOT.TB and tuberculin skin test. BMC Infect. Dis. 12,169.

15. Ponce de Leon, D. et al. (2008) Comparison of an interferon-gamma assay with tuberculin skin testing for detection of tuberculosis (TB) infection in patients with rheumatoid arthritis in a TB-endemic population. J. Rheumatol. 35, 776.

16. Pareek, M. et al. (2013) Community-based evaluation of immigrant tuberculosis screening using interferon-release assays and tuberculin skin testing: observational, study and economic analysis. Thorax 68, 230.

17. Wrighton-Smith, P., Sneed, L., Humphrey, F., Tao, X., Bernacki, E. (2012) Screening health care workers with interferon-release assay versus tuberculin skin test: impact on costs and adherence to testing (the SWITCH study). J. Occup. Environ. Med. 54, 806.

18. T-SPOT®.TB Package Insert. Oxford Immunotec Inc. 2013. PI-TT.610-US-V4.

19. Franken, W.P. et al. (2009) Variation in T-Spot.TB spot interpretations independent of different laboratories. Clin. Vaccine Immunol. 16, 1439.

20. Dorman, S.E. et al. (2014) Interferon-release assays and tuberculin skin testing for diagnosis of latent tuberculosis infection in healthcare workers in the United States. Am. J. Respir. Crit. Care Med. 189, 77.

21. Centers for Disease Control Regional Training and Medical Consultation Centers (RTMCCs) website. www.cdc.gov/tb/education/rtmc/ default.html. (accessed March, 12 2014).