WHO announces updates on new TB antigen-based skin tests for the diagnosis of TB infection

From WHO Official Website

A Guideline Development Group was convened by World Health Organization (WHO) from 31 January to 3 February 2022 to discuss the findings of the systematic reviews and to make recommendations on the three Mycobacterium tuberculosis(M.tb) specific antigen based diagnostic tests for TB infection including EC® (C-TST) manufactured by Anhui Zhifei Longcom, and the Group highly valued such products as well as the application prospects.

Tuberculosis antigen-based skin tests (TBST), a new class of tests to diagnose TB infection, have been assessed by the World Health Organization (WHO) and are found to be accurate, acceptable, feasible and cost-effective. These tests represent an alternative to tuberculin skin test (TST) and Interferon-Gamma Release Assays (IGRAs), and also represent a significant advancement to TST which has been used for over half a century.¹

According to WHO, over a quarter of the world’s population is estimated to be infected with Mycobacterium tuberculosis complex (MTBC). Tests for TB infection are useful to identify those high risk individuals who are most likely to benefit from TB preventive treatment (TPT)². The two currently available classes of tests – tuberculin skin test (TST) and interferon-gamma release assay (IGRA) – require a competent immune response to accurately identify TB infection. For TST, false positive results occur in patients who have received a bacille Calmette-Guérin (BCG) vaccination and those with non-tuberculous mycobacterial (NTM) infection. Compared with TST, IGRA is more specific, however it requires laboratory infrastructure and qualified personnel; also, it is more expensive.³

In summary, The new TBSTs using M.tb specific antigens ESAT6 and CFP10, (which are absent in BCG and most environmental mycobacteria), are with satisfactory sensitivity and specificity, they are easy to operate, do not require laboratory infrastructures and qualified personnel, and cost-effective, they are suitable for screening in large-scale population, indicating a good application prospect. Currently, the following TBSTs were included in the evaluation: C-Tb (Serum Institute of India, India); C-TST (formerly known as ESAT6-CFP10 test, Anhui Zhifei Longcom, China); and Diaskintest (Generium, Russian Federation).  Evidence suggests that these tests may offer similar specificity to IGRA, and when compared with TST they may provide more reliable results in children and in HIV-infected population.⁴

“The diagnostic options for people with TB infection are increasing thanks to manufacturer engagement and research generating new evidence. Ensuring that everyone in need can obtain a rapid and accurate diagnosis of TB infection will save lives and reduce suffering” said Dr Tereza Kasaeva, Director of WHO’s Global TB Program.⁵

Recombinant Mycobacterium Tuberculosis Fusion Protein (EC^®) (C-TST) is developed and manufactured by Anhui Zhifei Longcom Biopharmaceutical Co.,Ltd, a wholly owned subsidiary of Zhifei Biological Products Co.,Ltd. It is a national Class 1 new drug and is applicable to the diagnosis of M.tb infection. The diagnosis is not affected by BCG vaccination, thus being able to differentiate BCG vaccination and M.tb infection. It has been supported by National Major Project for Infectious Diseases. Recombinant Mycobacterium Tuberculosis Fusion Protein (EC^®) and Mycobacterium Vaccae for Injection (Vaccae^®) will provide new technologies, new tools and new strategies for the prevention and control of TB in China and the world.

Reference：

1. https://www.who.int/news/item/04-04-2022-who-announces-updates-on-new-tb-antigen-based-skin-tests-for-the-diagnosis-of-tb-infection

2. https://www.who.int/news/item/04-04-2022-who-announces-updates-on-new-tb-antigen-based-skin-tests-for-the-diagnosis-of-tb-infection

3. Rapid communication: TB antigen-based skin tests for the diagnosis of TB infection https://www.who.int/publications/i/item/WHO-UCN-TB-2022.1

4. Rapid communication: TB antigen-based skin tests for the diagnosis of TB infection https://www.who.int/publications/i/item/WHO-UCN-TB-2022.1

5.  https://www.who.int/news/item/04-04-2022-who-announces-updates-on-new-tb-antigen-based-skin-tests-for-the-diagnosis-of-tb-infection