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Latent tuberculosis infection (LTBI) is characterized by the presence of Mycobacterium tuberculosis bacteria without any symptoms of active disease. True or False: Individuals with LTBI are contagious.
Answer: False
Latent tuberculosis infection (LTBI) involves the presence of Mycobacterium tuberculosis bacteria without active disease symptoms. Crucially, individuals with LTBI are not contagious, as contagiousness is associated with active tuberculosis disease.
True or False: Individuals with latent tuberculosis infection (LTBI) pose a risk of transmitting the TB bacteria to others through exhalation.
Answer: False
Individuals with latent tuberculosis infection (LTBI) do not pose a risk of transmitting Mycobacterium tuberculosis bacteria to others. Transmission occurs only with active tuberculosis disease, typically through the exhalation of infectious droplets.
True or False: Tuberculosis bacteria can only remain dormant within the lungs.
Answer: False
Tuberculosis bacteria can remain dormant both inside and outside the lungs, in various sites throughout the body.
What is the defining characteristic of Latent Tuberculosis Infection (LTBI)?
Answer: Infection with Mycobacterium tuberculosis without symptoms of active disease, where the person is not contagious.
Latent tuberculosis infection (LTBI) is characterized by the presence of Mycobacterium tuberculosis bacteria within the body, but without the manifestation of active disease symptoms or contagiousness.
How does the contagiousness of Latent Tuberculosis Infection (LTBI) compare to that of Active Tuberculosis (TB)?
Answer: LTBI is not contagious, whereas active pulmonary TB is contagious.
A critical distinction is that latent tuberculosis infection (LTBI) is not contagious, meaning transmission does not occur. In contrast, active pulmonary tuberculosis is contagious, with bacteria spread primarily through exhalation.
In which parts of the body can TB bacteria remain dormant?
Answer: Both inside and outside the lungs.
Mycobacterium tuberculosis bacteria can remain dormant in various locations within the body, including both within the lungs and in extrapulmonary sites.
Which of the following is NOT recognized as a type of tuberculosis strain?
Answer: Partially drug-resistant tuberculosis (PDR TB)
The recognized categories of tuberculosis strains based on drug resistance are standard TB, multi-drug-resistant tuberculosis (MDR TB), extensively drug-resistant tuberculosis (XDR TB), and totally drug-resistant tuberculosis (TDR TB). 'Partially drug-resistant tuberculosis' is not a standard classification.
What is the concept of 'concomitant immunity' in the context of tuberculosis?
Answer: Protection against developing active TB after subsequent exposure, possibly due to memory T cells.
Concomitant immunity refers to the apparent protection against developing active TB disease after subsequent exposure to Mycobacterium tuberculosis, which is thought to be mediated by tissue-resident memory T cells in individuals with latent infection.
True or False: A person diagnosed with active pulmonary tuberculosis can transmit the bacteria to others through casual contact, such as sharing utensils.
Answer: False
Transmission of active pulmonary tuberculosis occurs primarily through the air via exhaled droplets, not through casual contact like sharing utensils. Casual contact is generally insufficient for transmission.
True or False: Approximately one-quarter of the global population is estimated to be living with either latent or active tuberculosis infections as of 2023.
Answer: True
As of 2023, it is estimated that approximately one-quarter of the world's population is living with either latent or active tuberculosis (TB) infections, indicating a substantial global burden.
True or False: Tuberculosis infection rates are uniform across all countries, with similar percentages of the population testing positive for TB globally.
Answer: False
Tuberculosis infection rates vary significantly worldwide. For example, prevalence is much higher in many Asian and African countries compared to the United States.
True or False: About half of all individuals exposed to pulmonary TB eventually develop active disease.
Answer: False
While approximately one-third of individuals exposed to pulmonary TB become infected, only about 10% of those infected will develop active TB disease during their lifetime. The risk is not as high as half.
True or False: The World Health Organization (WHO) currently estimates that approximately a quarter of the world's population is actively infected with tuberculosis and at high risk of developing active disease.
Answer: False
The World Health Organization (WHO) has clarified its estimates. While approximately a quarter of the global population has *been* infected with tuberculosis, the organization no longer confidently estimates that this large proportion is currently actively infected and at high risk of developing active disease. The risk of progression from past infection is now understood to be more variable and potentially lower than previously assumed for many individuals.
What proportion of the global population is estimated to be living with either latent or active tuberculosis infections?
Answer: Approximately 25%
It is estimated that approximately one-quarter, or 25%, of the world's population is living with either latent or active tuberculosis infections, indicating a substantial global burden.
Which geographical areas exhibit a significantly higher prevalence of positive tuberculin tests compared to the United States?
Answer: Many Asian and African countries
While only about 5% to 10% of the US population tests positive for TB, approximately 80% of the population in many Asian and African countries test positive, indicating a substantially higher prevalence of infection in these regions.
What is the primary mode of transmission for tuberculosis between individuals?
Answer: Through the air when an individual with active pulmonary TB exhales bacteria.
Tuberculosis is primarily transmitted through the air when a person with active pulmonary TB exhales bacteria. These infectious droplets can be inhaled by others, leading to infection.
Following infection with the TB bacteria, what is the approximate lifetime risk of developing active TB disease?
Answer: About 10%
While approximately one-third of individuals exposed to pulmonary TB become infected, only about 10% of those infected will develop active TB disease during their lifetime.
True or False: Human Immunodeficiency Virus (HIV) infection is considered the single greatest risk factor for latent TB progressing to active disease.
Answer: True
Human Immunodeficiency Virus (HIV) infection is recognized as the greatest known risk factor for the progression of latent TB to active disease, significantly compromising the immune system's ability to control the bacteria.
True or False: Aging is considered a protective factor that decreases the risk of latent TB reactivation due to improved immune function in older adults.
Answer: False
Aging is generally considered a risk factor that *increases* the likelihood of latent TB reactivation, as immune function tends to decline with age, making the body less effective at controlling dormant bacteria.
True or False: Comorbid conditions like diabetes and HIV significantly decrease the risk of latent TB progressing to active disease.
Answer: False
Comorbid conditions such as diabetes and HIV significantly *increase* the risk of latent TB progressing to active disease, as they often compromise immune function.
Which of the following conditions significantly increases the risk of latent TB progressing to active disease?
Answer: Human Immunodeficiency Virus (HIV) infection
Human Immunodeficiency Virus (HIV) infection is recognized as the greatest known risk factor for the progression of latent TB to active disease, significantly compromising the immune system's ability to control the bacteria.
Which of the following is NOT listed as a factor that increases the risk of latent TB progressing to active disease?
Answer: Recent BCG vaccination
While conditions like diabetes, malnutrition, and advanced age are recognized risk factors for LTBI progression, recent BCG vaccination is not typically cited as a factor that increases this risk; in fact, it can complicate TST interpretation.
True or False: The BCG vaccine can interfere with the interpretation of tuberculin skin tests (TSTs) by potentially causing a false-positive reaction.
Answer: True
The Bacillus Calmette-Guérin (BCG) vaccine, administered in many countries, can indeed interfere with the interpretation of tuberculin skin tests (TSTs) by potentially eliciting a false-positive reaction.
True or False: Interferon-gamma release assays (IGRAs) are unaffected by previous BCG vaccination when diagnosing latent TB infection.
Answer: True
Interferon-gamma release assays (IGRAs) are blood tests that measure the immune response to specific TB antigens and are not affected by prior BCG vaccination, making them a valuable diagnostic tool in BCG-vaccinated populations.
True or False: Tuberculin skin tests (TSTs) and Interferon-gamma release assays (IGRAs) are the two primary classes of diagnostic tests for latent TB infection.
Answer: True
The two primary classes of diagnostic tests used to identify latent TB infection (LTBI) are tuberculin skin tests (TSTs), such as the Mantoux test, and Interferon-gamma release assays (IGRAs).
True or False: Tuberculin conversion indicates that a person's immune system has recently encountered tuberculosis bacteria, resulting in a positive skin test after a previous negative one.
Answer: True
Tuberculin conversion signifies a change from a negative tuberculin skin test (TST) result to a positive one, typically indicating a recent infection with the tuberculosis bacteria.
True or False: The 'boosting phenomenon' in tuberculin skin tests refers to a situation where a person's immune response becomes stronger over time, leading to a more accurate diagnosis of latent TB.
Answer: False
The 'boosting phenomenon' can lead to a stronger reaction on a subsequent TST, potentially mimicking a new infection and complicating diagnosis, rather than inherently leading to a more accurate diagnosis of latent TB.
True or False: In the US, guidelines typically recommend ignoring a history of BCG vaccination when interpreting tuberculin skin test results.
Answer: True
US guidelines often advise ignoring BCG vaccination history when interpreting TST results, prioritizing risk stratification for treatment over accounting for potential vaccine-induced reactions.
True or False: The Mantoux test is considered more reliable than Interferon-gamma release assays (IGRAs) for diagnosing latent TB infection because it is not affected by prior BCG vaccination.
Answer: False
The Mantoux test (a type of TST) *is* affected by prior BCG vaccination, potentially causing false positives. IGRA tests are generally considered more reliable in BCG-vaccinated individuals because they are not affected by the vaccine.
True or False: The primary purpose of drawing a waterproof ink mark around the Mantoux test injection site is to prevent infection at the site.
Answer: False
The primary purpose of the waterproof ink mark around the Mantoux test injection site is to facilitate accurate identification and measurement of the induration (swelling) when the test is read 48 to 72 hours later, not to prevent infection.
True or False: The Heaf test, a type of tuberculin skin test, was discontinued primarily due to concerns about its accuracy compared to the Mantoux test.
Answer: False
The Heaf test was discontinued primarily because its manufacturer found production to be financially unsustainable, not due to concerns about its accuracy relative to the Mantoux test.
True or False: The US approach to interpreting TST results generally prioritizes identifying potential new infections over accounting for the effects of prior BCG vaccination.
Answer: True
US guidelines often advise ignoring BCG vaccination history when interpreting TST results, focusing instead on risk stratification to identify individuals who may require treatment, thereby prioritizing the identification of potential new infections or reactivations.
Which diagnostic test for latent TB infection is known to be unaffected by prior BCG vaccination?
Answer: Interferon-gamma release assay (IGRA)
Interferon-gamma release assays (IGRAs) are blood tests that measure the immune response to specific TB antigens and are not affected by prior BCG vaccination, unlike tuberculin skin tests (TSTs).
How does the US approach to BCG vaccination history in TST interpretation generally differ from UK guidelines?
Answer: The US often ignores BCG history, while UK guidelines may acknowledge its effect.
US guidelines frequently recommend ignoring BCG vaccination history when interpreting TST results, focusing on risk assessment. In contrast, UK guidelines may consider the potential impact of BCG on TST results more directly.
What is the significance of the 'boosting phenomenon' in relation to tuberculin skin tests (TSTs)?
Answer: It can lead to a stronger reaction on a subsequent TST, potentially mimicking a new infection.
The 'boosting phenomenon' refers to the observation that a prior TST can sometimes enhance the immune response to a subsequent TST, potentially leading to a stronger reaction that might be misinterpreted as a recent infection (tuberculin conversion).
What does 'tuberculin conversion' signify in the context of TB testing?
Answer: A positive reaction on a TST after previously having a negative reaction.
Tuberculin conversion indicates a change from a negative tuberculin skin test (TST) result to a positive one, typically signifying a recent infection with the tuberculosis bacteria.
What is the primary difference between the Mantoux test and Interferon-gamma release assays (IGRAs) for diagnosing latent TB infection?
Answer: Mantoux is affected by BCG, IGRA is not.
A key distinction is that the Mantoux test (a TST) can be affected by prior BCG vaccination, potentially yielding false positives, whereas IGRA tests are not influenced by BCG vaccination.
What was the primary reason cited for the discontinuation of the Heaf test?
Answer: Its manufacturer found production financially unsustainable.
The Heaf test, a type of tuberculin skin test, was discontinued primarily due to the manufacturer finding its production financially unsustainable, rather than issues with its accuracy relative to the Mantoux test.
What is the primary significance of the induration measured in a Mantoux test?
Answer: It represents a hard swelling at the injection site, indicating an immune response to TB bacteria.
The induration, a hard swelling at the Mantoux test injection site, is the key measurement indicating a cellular immune response to Mycobacterium tuberculosis, suggesting prior exposure or infection.
True or False: The primary goal of treating latent tuberculosis infection (LTBI) is to eliminate the bacteria completely from the body, guaranteeing no future risk of active disease.
Answer: False
The primary goal of treating LTBI is to prevent the progression to active disease. While highly effective, treatment does not guarantee complete eradication of all bacteria, and a minimal residual risk may persist.
True or False: The 2-month regimen of rifampicin and pyrazinamide (2RZ) is currently recommended as a safe and effective treatment option for LTBI.
Answer: False
The 2-month regimen of rifampicin and pyrazinamide (2RZ) is no longer recommended as a safe and effective treatment option for LTBI due to safety concerns.
True or False: The 3HP treatment regimen involves taking rifapentine and isoniazid weekly for three months and is considered an effective alternative for LTBI.
Answer: True
The 3HP regimen, consisting of weekly rifapentine and isoniazid for three months, is recognized as an effective alternative treatment option for latent tuberculosis infection (LTBI).
True or False: Adhering strictly to LTBI treatment regimens is unimportant, as the medication primarily prevents future infections rather than treating existing dormant ones.
Answer: False
Strict adherence to LTBI treatment regimens is critically important. The medication aims to prevent the progression of existing dormant infections to active disease and to reduce the likelihood of developing drug resistance if the infection reactivates.
True or False: Treating active tuberculosis with latent TB infection (LTBI) regimens is a recommended practice for managing drug-resistant strains.
Answer: False
Treating active tuberculosis with LTBI regimens is strongly discouraged. It is an inadequate treatment for active disease and carries a significant risk of promoting the development of drug-resistant tuberculosis strains.
True or False: Directly Observed Therapy (DOT) is recommended for intermittent LTBI treatment regimens to ensure patient adherence.
Answer: True
Directly Observed Therapy (DOT) is recommended for intermittent LTBI treatment regimens, such as the 3HP regimen, to ensure patient adherence and successful completion of therapy.
What is the primary objective of treating latent tuberculosis infection (LTBI)?
Answer: To prevent the progression of infection to active tuberculosis disease.
The principal goal of treating latent tuberculosis infection (LTBI) is to prevent the dormant bacteria from becoming active and causing disease, thereby reducing the overall burden of tuberculosis.
Which of the following is a recognized treatment regimen for latent tuberculosis infection (LTBI)?
Answer: 4 months of rifampicin (4R)
The 4-month regimen of rifampicin (4R) is one of the recognized treatment options for latent tuberculosis infection (LTBI).
What is the primary concern regarding the treatment of active TB with latent TB infection (LTBI) regimens?
Answer: It poses a significant risk of promoting the development of drug-resistant TB strains.
Treating active tuberculosis with LTBI regimens is problematic because it is insufficient for controlling the active disease and carries a substantial risk of fostering the emergence of drug-resistant tuberculosis strains.
What is the primary reason for ruling out active tuberculosis before initiating treatment for latent TB infection (LTBI)?
Answer: To prevent the development of drug-resistant TB strains.
It is crucial to rule out active TB before starting LTBI treatment because treating active disease with LTBI regimens is inadequate and carries a significant risk of promoting the development of drug-resistant tuberculosis strains.
What is considered the 'gold standard' treatment regimen for latent tuberculosis infection (LTBI)?
Answer: 9 months of isoniazid (9H).
The regimen of nine months of isoniazid (9H) is widely regarded as the 'gold standard' treatment for latent tuberculosis infection (LTBI) due to its established efficacy in preventing progression to active disease.
What is the role of Directly Observed Therapy (DOT) in the context of LTBI treatment regimens?
Answer: It ensures adherence for intermittent LTBI regimens like 3HP.
Directly Observed Therapy (DOT) is recommended for intermittent LTBI treatment regimens, such as the 3HP regimen, to ensure patient adherence and successful completion of therapy.
What is the consequence of not completing LTBI treatment regimens as prescribed?
Answer: The likelihood of a successful outcome decreases, and drug resistance may develop.
Failure to complete LTBI treatment regimens as prescribed significantly decreases the likelihood of a successful outcome and increases the risk of developing drug-resistant tuberculosis if the infection reactivates.
True or False: The 'ticking time bomb' theory suggests that latent TB infections pose a minimal long-term risk, as the bacteria typically die off within a few years.
Answer: False
The 'ticking time bomb' theory suggests the opposite: that latent TB infections represent a significant reservoir of future active TB cases and thus pose a substantial long-term risk, necessitating aggressive treatment.
True or False: Research suggests that individuals infected with Mycobacterium tuberculosis for over two years have a very low probability of developing active TB, challenging the 'ticking time bomb' concept.
Answer: True
Counterarguments to the 'ticking time bomb' theory cite research indicating that most individuals infected with Mycobacterium tuberculosis for over two years have a very low probability of developing active TB, questioning the long-term progression risk for many latent infections.
What does the 'ticking time bomb' theory suggest about latent TB infections?
Answer: Latent TB represents a reservoir for future active TB cases.
The 'ticking time bomb' theory posits that latent TB infections constitute a significant reservoir of future active TB cases, implying a substantial ongoing risk that warrants proactive treatment.
What is the primary argument presented against the 'ticking time bomb' theory of latent TB?
Answer: Studies show most individuals infected for over two years do not develop active TB.
A key counterargument to the 'ticking time bomb' theory is that studies suggest most individuals infected with Mycobacterium tuberculosis for more than two years have a very low probability of developing active TB, questioning the long-term progression risk for many latent infections.
What does the World Health Organization's (WHO) updated stance on latent TB suggest?
Answer: The lifetime risk of developing active TB from past infection is less certain than previously estimated.
The WHO's updated position indicates a shift in understanding, suggesting that the lifetime risk of developing active TB from a past infection is less certain and potentially lower than previously estimated for many individuals.
True or False: Symptoms of extrapulmonary tuberculosis, such as TB in the brain, typically appear suddenly and are immediately severe.
Answer: False
Symptoms of extrapulmonary tuberculosis often develop slowly and may be overlooked until they become severe, rather than appearing suddenly and being immediately debilitating.
What is a characteristic feature of symptom development in extrapulmonary tuberculosis?
Answer: They often develop slowly and may be ignored until severe.
Symptoms of extrapulmonary tuberculosis, which affects sites outside the lungs, often develop gradually and may be overlooked or mistaken for other conditions until they become severe, making diagnosis challenging.
What is the primary implication if TB bacteria reactivate outside the lungs (extrapulmonary TB)?
Answer: Symptoms often develop slowly and may be overlooked until severe.
When TB reactivates outside the lungs, the resulting extrapulmonary tuberculosis often presents with symptoms that develop gradually and may be overlooked until they become severe, making diagnosis challenging.