Frequently Asked Questions for laboratories

A brochure addresses questions pertaining to blood collection and incubation, performance of the QFT-Plus ELISA, and QFT-Plus data analysis is available for download using the link below.


Below you may also find answers to common questions regarding the launch of QuantiFERON-TB Gold Plus and the QFT to QFT-Plus transition.

What is QuantiFERON-TB Gold Plus (QFT-Plus)?

Overall, QFT-Plus is very similar to the previous In-Tube (QFT) version – the intended use remains the same. The difference is mainly in the custom blood collection tubes. The Nil and Mitogen tubes remain the same, but the TB Antigen tube has been changed. With QFT-Plus, there are now two TB Antigen tubes – TB Antigen Tube 1 (TB1) optimized to stimulate a CD4 immune response and TB Antigen Tube 2 (TB2) optimized to stimulate both CD4 and CD8 immune responses.

How does QFT-Plus differ from QFT?

With the addition of proprietary CD8 antigens, QFT-Plus represents a key milestone in the development of diagnostic tests for latent TB infection. For the first time, a test has been shown to offer the potential ability to capture a much broader picture of an individual’s immune response to TB infection.

Why CD8?

During Mycobacterium tuberculosis (MTB) infection, CD4 T cells play a critical role in immunological control through their secretion of the cytokine IFN-y. Evidence now supports a role for CD8 T cells participating in the host defense to MTB by producing IFN-y and other soluble factors, which activate macrophages to suppress growth of MTB, kill infected cells, or directly lyse intracellular MTB (1–3). IFN-y producing MTB-specific CD8 cells have been detected in subjects with LTBI and with active TB (4–7). In addition, MTB-specific CD8 T cells producing IFN-y have also been detected in active TB subjects with HIV co-infection (8, 9) and in young children with TB disease (10).

What are the QFT-Plus workflow improvements?

With QFT-Plus, laboratories may now choose to offer a new single lithium heparin blood collection option.

Is QFT-Plus replacing QFT?

Yes, QFT-Plus will replace QFT. For customers currently running QFT, QIAGEN will assist in the transition from QFT to QFT-Plus to ensure an easy, successful implementation.

Is the ELISA procedure different?

No, the ELISA procedure is the same as for QFT.

Can't find the answer to your question?

Contact a QFT-Plus expert


  1. Turner, J. et al. (1996) Stimulation of human peripheral blood mononuclear cells with live Mycobacterium bovis BCG activates cytolytic CD8+ T cells in vitro. Immunology 87, 339.
  2. Brookes, R.H. et al. (2003) CD8+ T cell-mediated suppression of intracellular Mycobacterium tuberculosis growth in activated human microphages. Eur. J. Immunol. 33, 3293.
  3. Stenger, S. et al. (1998) An antimicrobial activity of cytolytic T cells mediated by granulysin. Science 282, 121.
  4. Lalvani, A. et al. (1998) Human cytolytic and interferon gamma-secreting CD8+ T lymphocytes specific for Mycobacterium tuberculosis. Proc. Natl. Acad. Sci. U.S.A. 95, 270.
  5. Lewinsohn, D.M. et al. (2001) Classically restricted human CD8+ T lymphocytes derived from Mycobacterium tuberculosis-infected cells: definition of antigenic specificity. J. Immunol. 166, 439.
  6. Lewinsohn, D.A. et al. (2007) Immunodominant tuberculosis CD8 antigens preferentially restricted by HLA-B. PLoS Pathol. 3, 1240.
  7. Barcellini, L. et al. (2016) First independent evaluation of QuantiFERON-TB Plus performance. Eur. Respir. J. 47, 1587-1590.
  8. Chicchio, T. et al. (2014) Polyfunctional T-cells and effector memory phenotype are associated with active TB in HIV-infected patients. J. Infect. doi: 10.1016/j.jinf.2014.06.009. Epub
  9. Ongaya, A. et al. (2013) Mycobacterium tuberculosis-specific CD8+ T cell recall in convalescing TB subjects with HIV co-infection. Tuberculosis 93, S60.
  10. Lanicioni, C. et al. (2012) CD8+ T cells provide an immunologic signature of tuberculosis in young children. Am. J. Respir. Crit. Care Med. 185, 206

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