Authors: Madhukar Pai, MD, PhD—Author and Series Editor; Camila Rodrigues, MD—co-author
Number of pages: 4
Download (2018, pdf, 132kb)
Overview: Most individuals who get exposed to Mycobacterium tuberculosis (MTB) manage to eliminate or contain the infection using host T-cell immune defenses. However, some MTB bacilli may remain viable (latent) and “reactivate” later to cause active TB disease. This state is called Latent TB Infection (LTBI). Identification and treatment (i.e. preventive therapy or prophylaxis) of LTBI can substantially reduce the risk of development of active disease (by as much as 60%). However, because 40% of Indians are latently infected, LTBI screening must be restricted to specific high risk populations in India, where the benefits of LTBI treatment outweigh any risks. These include people living with HIV, adult and child contacts of pulmonary TB cases, patients initiating anti-tumour necrosis factor (TNF-alpha) treatment, patients with end stage renal failure on dialysis, patients preparing for organ or haematologic transplantation, and patients with silicosis. While either tuberculin skin test (Mantoux) or interferon-gamma release assays (e.g., TB Gold) can be used for LTBI screening, it is important to make sure that these tests are not used for active TB diagnosis. For persons with symptoms or abnormal chest x-rays, physicians should order smears, cultures, and molecular tests (e.g., Xpert MTB/RIF). If LTBI is diagnosed, then physicians must rule-out TB disease with chest x-rays before starting one of the recommended drug regimens. It is important to ensure adherence, and provide adequate counseling to ensure that patients do not stop therapy prematurely.
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Management of Latent Tuberculosis Infection
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Question 1 of 5
1. Question
What is the estimated prevalence of latent TB infection in India?
Correct
The correct answer is (c). An estimated 40% of the Indian population is estimated to be latently infected, using tuberculin surveys.
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The correct answer is (c). An estimated 40% of the Indian population is estimated to be latently infected, using tuberculin surveys.
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Question 2 of 5
2. Question
Which of the following tests can be used to screen for latent TB infection?
Correct
The correct answer is (d). The tuberculin skin test, using Mantoux technique, is one of the two accepted tests for latent TB infection screening. The other test is interferon-gamma release assays (e.g., TB Gold)
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The correct answer is (d). The tuberculin skin test, using Mantoux technique, is one of the two accepted tests for latent TB infection screening. The other test is interferon-gamma release assays (e.g., TB Gold)
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Question 3 of 5
3. Question
Which of these high-risk populations should be targeted for LTBI screening and treatment?
Correct
The correct answer is (e). Latent TB screening should be restricted to high-risk groups. These include people living with HIV and AIDS, adult and child contacts of pulmonary TB cases, patients initiating anti-tumour necrosis factor (TNF-alpha) treatment, patients with end stage renal failure on dialysis, patients preparing for organ or haematologic transplantation, and patients with silicosis.
Incorrect
The correct answer is (e). Latent TB screening should be restricted to high-risk groups. These include people living with HIV and AIDS, adult and child contacts of pulmonary TB cases, patients initiating anti-tumour necrosis factor (TNF-alpha) treatment, patients with end stage renal failure on dialysis, patients preparing for organ or haematologic transplantation, and patients with silicosis.
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Question 4 of 5
4. Question
Which of the following statements is TRUE about interferon-gamma release assays (e.g., TB Gold)?
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The correct answer is (a). IGRAs cannot separate latent infection from active TB, and, therefore, not recommended for active TB detection. This is also true for Mantoux skin test. Both IGRAs and TST should be restricted to LTBI screening, and should not be used for active TB diagnosis. In children, Mantoux test may have some value as a test for infection, in addition to chest x-rays, symptoms, history of contact, and other microbiological investigations (e.g., gastric juice acid fast bacilli and Xpert MTB/RIF).
Incorrect
The correct answer is (a). IGRAs cannot separate latent infection from active TB, and, therefore, not recommended for active TB detection. This is also true for Mantoux skin test. Both IGRAs and TST should be restricted to LTBI screening, and should not be used for active TB diagnosis. In children, Mantoux test may have some value as a test for infection, in addition to chest x-rays, symptoms, history of contact, and other microbiological investigations (e.g., gastric juice acid fast bacilli and Xpert MTB/RIF).
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Question 5 of 5
5. Question
Which of the following drug regimens are NOT recommended for latent TB infection?
Correct
The correct answer is (e). The HRZE drug regimen is meant for treating active tuberculosis. For latent TB infection, treatment options recommended by WHO include 6 to 9 months of isoniazid, 3-month regimen of weekly rifapentine plus isoniazid, or 3–4 months isoniazid plus rifampicin, or 3–4 months rifampicin alone.
Incorrect
The correct answer is (e). The HRZE drug regimen is meant for treating active tuberculosis. For latent TB infection, treatment options recommended by WHO include 6 to 9 months of isoniazid, 3-month regimen of weekly rifapentine plus isoniazid, or 3–4 months isoniazid plus rifampicin, or 3–4 months rifampicin alone.
Content was good and well summarized but just limited to Indian experience. In fact WHO had recommended the usage of INH prophylaxis but then few countries have moved forward. We just started pushing the implementation in Swaziland since 2012 and now under the HIV & AIDS program this is a well monitored activity in preventing PLWH from getting active TB. Baylor in Swaziland went as far as conducting a survey on children and INH prophylaxis effectiveness with excellent outcome. I designed for the program an IPT card to engage patient in monitoring the IPT ( Isonizid Prophylaxis Therapy) and just remaining approval to pass as a national tool. Few other matters to mention are the pill burden in people on ARVs; ADR (adverse drug reactions) as well like mental condition when on Effavirenz or increased liver toxicity when on Niverapine. Again all these need systematic studies to really measure the benefits which of course remain greater then complications.