Search Results: Displaying all About TB (6)

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What is latent TB? And how is it different from active TB disease? 2013 Latent TB infection (LTBI) is considered a ‘carrier state’ of M. tuberculosis infection where an individual silently carries the TB bacteria in their body. In LTBI, the infection is well contained by the host’s immune system. Hence, unlike active TB, individuals with LTBI are asymptomatic, and not contagious to others. However, this condition may progress or reactivate to active disease in the future. As the development of TB disease depends on a variety of risks and medical conditions, individuals with LTBI are commonly offered preventative therapy to prevent active disease from occurring. Preventative treatment is an important strategy to reduce TB morbidity and rates in many countries. Active TB is a disease state of uncontrolled M. tuberculosis growth which occurs when TB bacteria are able to overcome a person’s immune system. Active TB can affect any organ of the body, but is most commonly a disease of the lung. A person with active TB will often have symptoms which are not specific for tuberculosis (e.g. a cough, night sweats and weight loss). Direct detection of M. tuberculosis bacilli in sputum or specimen culture is the hallmark of disease and is considered the gold standard of TB diagnosis. A person who has active pulmonary TB and is coughing, with the presence of M. tuberculosis in their sputum is infectious. QFT is an assay that detects TB infection by measuring the cell mediated immune response to TB-specific antigens. It can be used as a diagnostic aid for M. tuberculosis complex infection, whether active tuberculosis disease or LTBI, however, when using QFT in a person suspected of having active TB, it should not replace appropriate microbiological and molecular investigation. QFT cannot distinguish between active and latent TB infection and should therefore never be used as a sole diagnostic test.
What is TB? 2013 Tuberculosis (TB) is an airborne disease caused by infection with Mycobacterium tuberculosis complex organisms (M. tuberculosis, M.bovis and M.africanum). The transmission of TB occurs through the inhalation of droplets that are either coughed or sneezed from an individual infected with active TB disease of the lung (active pulmonary TB). Not everyone who becomes infected with TB bacteria develops active TB disease.
What is the meaning of remote TB infection and can QFT distinguish between remote and recent infection? 2013 The term remote infection is an ill-defined term that is increasingly being used in the TB community. For most, it appears that remote infection relates to old TB infection that may have been cleared by the individual, however, some may interpret it as meaning old TB infection that can still reactivate to TB disease. As with the TST, QFT cannot distinguish between remote and new infection.
Why is latent TB infection important? 2013 It is estimated that up to 10% of people infected with M. tuberculosis will develop active TB in their lifetime. With an estimated 2 billion people (or one third of the world’s population) infected, the large global reservoir of LTBI represents a huge pool of contagious disease. Diagnosing LTBI, and preventive treatment, can significantly reduce the risk of disease, and prevent outbreaks from recent transmission. On a global level, achieving a significant reduction in the burden of TB cases cannot be achieved without also including the detection and treatment of LTBI.
How should screening for TB and LTBI be prioritized? 2013 Prioritized or targeted TB screening focuses on screening individuals and populations at highest risk of being infected, progressing or reactivating TB disease, or having both risks present. The purpose of TB screening is to find cases at an early asymptomatic phase that is easily curable and find LTBI among individuals who may benefit from preventive treatment. Targeted testing can be applied as follows: 1. Contact investigation: Identifying newly infected contacts top the priority list as the risk of infection is high and new infection carries a much higher risk of disease progression compared to old or chronic infection. Contact investigation is a WHO recommendation. 2. Congregate settings: Congregate settings are places where transmission of communicable diseases is a real risk. Focused screening for disease and LTBI prior to entry into congregate settings reduces TB transmission through early identification of TB and preventive treatment of those at risk of developing disease in that setting. Congregate settings may include: „„hospitals/healthcare institutions „„residential facilities „„prisons/correctional facilities „„renal dialysis units „„homeless shelters „„higher educational facilities „„military barracks „„ certain settings of employment such as the mining industry. 3. Populations with high prevalence of TB infection: Targeted screening of individuals that are at high risk of being infected, such as individuals from TB endemic countries entering low burden countries or known populations with higher TB prevalence such as impoverished, homeless persons can make a significant individual and public health impact, especially when TB prevention is focused on those with LTBI that have clinical conditions that increase the risk of TB disease progression or reactivation. 4. Clinical conditions that increase the risk of developing TB disease: Prevention of disease in these individuals with LTBI prevents the need for long multi-drug treatment regimens and protects against developing lung and organ destruction, long term disability, death, economic loss and transmission of disease to family and those close to the individual. Individuals with LTBI and medical co-morbidities should be targeted for LTBI treatment after active tuberculosis has been excluded by thorough medical evaluation and radiography. Similarly, patients with TB infection should be targeted for LTBI treatment before initiation of immune suppressive therapy. This also applies to individuals newly infected from recent exposure to TB, such as contacts of known active TB cases, especially child contacts under 5 years of age.
Doesn’t everybody in high incidence countries have latent TB? 2013 No, this is a common misconception. 1 in 3 people worldwide is thought to be infected with LTBI, although there is significant variance in high incidence countries based on the demographics of the population being studied.


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