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Detection of latent TB infection key to preventing the spread of the disease

Presented by
Prof. Tuula Vasankari, University of Turku, Finland
NLC 2022
As the incidence of tuberculosis (TB) in the Nordic countries is low, the knowledge of the disease in this region of the world is waning both amongst professionals as well as in the general public. Nevertheless, latent TB poses a serious health threat which requires adequate management.

Prof. Tuula Vasankari (University of Turku, Finland) delivered an update on latent TB, which can be defined as a persistent immune response to stimulation by M. tuberculosis antigens with no evidence of clinically active TB disease. “TB is very common, as approximately a quarter of the world’s population is infected with TB,” Prof. Vasankari stated. “It is often hard to identify TB-infected individuals - especially since in latent TB infection there is usually a lack of clinical signs and symptoms.” Nevertheless, identification of individuals with latent TB infection is an important goal in TB elimination. “Treatment of latent TB infection can curb the development of active disease and can thus prevent further spread of TB [1].”

Targeted testing for TB can be used as a TB control strategy to identify and treat individuals at high risk for latent TB infection, and those at high risk for developing TB disease once infected with M. tuberculosis. “Once you decide to apply targeted testing, then you decide to treat,” Prof. Vasankari said. Latent TB infection can be diagnosed by a Mantoux tuberculin skin test and interferon-gamma release assay (IGRA) blood test; both tests assess an individual’s immune reactivity to M. tuberculosis. “TB testing activities should only be performed when there is a plan for care or follow-up. This means that healthcare workers should only test those individuals who are at high risk for developing TB disease; people not at high risk should generally not be tested.” Eligible populations for targeted testing include pregnant immigrant women from highly endemic areas who have a positive IGRA test within 2 years upon arrival in a Nordic country, and/or who have other diseases, and/or pulmonary X-ray indicative of previous TB, and/or who are newly exposed to infectious TB. Patients planned for immunosuppressive treatment or organ transplantation who have a positive purified protein derivative or IGRA test, and/or pulmonary X-ray indicative of previous TB, and/or a suspect medical history or previous exposure also qualify for testing. The same applies for patients with HIV and a positive purified protein derivative or IGRA test.

Prof. Vasankari emphasised that anyone with TB symptoms or a positive Mantoux tuberculin skin test or a positive IGRA blood test should be evaluated for TB disease. “Clinical evaluation of TB includes medical history, physical examination, tests for TB infection, chest X-ray, and bacteriological examination.” Regarding pharmacological treatment, the currently approved regimens consist of daily isoniazid monotherapy for 6–9 months, daily rifampicin plus isoniazid for 3 months, daily rifampicin monotherapy for 4 months, daily rifapentine plus isoniazid for 1 month, and weekly rifapentine plus isoniazid for 3 months [2,3]. In addition, drug-resistance and regular patient monitoring should further guide personalized TB treatment.

  1. Sterling TR, et al. MMWR Recomm Rep. 2020;69(1):1–11.
  2. WHO. WHO consolidated guidelines on tuberculosis. Module 4: Treatment Drug-susceptible tuberculosis treatment. 2021 https://www.tbonline.info/media/uploads/documents/ds-tb_who_guidelines.pdf
  3. Vasankari T. Latent tuberculosis-an update. Nordic Lung Congress 2022, 01–03 June, Copenhagen, Denmark.


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