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Tuberculosis (TB) is a serious infectious disease caused by the bacterium Mycobacterium tuberculosis. It primarily affects the lungs (pulmonary TB), but it can also spread to other parts of the body, such as the brain, kidneys, bones, and lymph nodes (extrapulmonary TB). TB is both preventable and curable with appropriate treatment.

• Transmission: TB spreads through airborne droplets when an infected person with active TB coughs, sneezes, talks, or sings. Inhaling these droplets can lead to infection.

• Not Contagious in Latent TB: People with latent TB do not spread the disease because the bacteria are inactive in their bodies.

•  Latent TB Infection (LTBI):

• The bacteria are present but inactive.
• The person has no symptoms and is not contagious.
• Can progress to active TB if untreated.

• Active TB Disease:

• The bacteria multiply and cause symptoms.
• The person is contagious if it involves the lungs or throat.

•  Pulmonary TB (most common):

• Persistent cough (lasting 3 weeks or longer)
• Coughing up blood or sputum
• Chest pain during breathing or coughing
• Fatigue and weakness
• Fever and night sweats
• Loss of appetite and weight loss

• Extrapulmonary TB (other organs):

• Symptoms vary based on the organ affected, e.g., back pain (spine), swollen lymph nodes, or headaches (if in the brain).

• Weakened immune system (e.g., HIV/AIDS, diabetes, cancer treatments)
• Close contact with someone who has active TB
• Living in or traveling to areas with high TB prevalence
• Poor nutrition and living conditions
• Smoking and substance use

• Early diagnosis and treatment of active cases to stop spread.
• Vaccination with Bacillus Calmette-Guérin (BCG) in high-prevalence areas.
• Proper ventilation and wearing masks in crowded places.

Tuberculosis remains a significant global health challenge, but it is treatable and preventable with appropriate medical care and public health measures.

TB screening typically includes several components to assess an individual's risk for tuberculosis and detect potential infection or active disease. 

Here's what TB screening generally includes:

[1] Risk Assessment: 

Your healthcare provider will conduct an individual TB risk assessment, which involves:

• Evaluating potential exposure to TB
• Assessing factors that increase risk of TB infection or progression to active disease
• Reviewing medical history and any previous TB testing

[2] Symptom Evaluation: 

The screening process includes checking for symptoms of active TB disease, such as:

• Persistent cough (lasting 3 weeks or longer)
• Chest pain
• Coughing up blood or sputum
• Fatigue
• Weight loss
• Fever
• Night sweats

[3] TB Testing: 

There are two main types of tests used for TB screening:

  TB Skin Test (TST)

• A small amount of testing material is injected under the skin
• The injection site is checked for a reaction after 48-72 hours

  TB Blood Test (IGRA)

• A blood sample is taken and analyzed for immune response to TB bacteria
• Results are usually available within 24-48 hours

[4] Additional Evaluation

If the initial screening tests are positive or if symptoms suggest active TB, further evaluation may be necessary:

- Chest X-ray to check for lung abnormalities

- Sputum tests to detect TB bacteria in the lungs

- Additional blood tests or imaging studies as needed

It's important to note that a positive screening test doesn't necessarily mean you have active TB disease. It indicates that you have been exposed to TB bacteria and may have a latent TB infection. Further evaluation is required to determine if you have active TB disease and need treatment[1][2][3].

The frequency of TB testing depends on several factors, including an individual's risk level and workplace requirements. 

Here are the key points regarding how often TB tests should be done:

General Guidelines

For most people, routine annual TB testing is no longer recommended unless there are specific risk factors or exposures. The Centers for Disease Control and Prevention (CDC) has updated its recommendations to focus on baseline testing and symptom screening rather than frequent repeat testing[3][4].

Healthcare Workers

- All healthcare personnel should receive TB screening upon hire (baseline screening).

- Annual TB testing is not recommended for healthcare workers unless there is a known exposure or ongoing transmission in their healthcare facility[3][4].

- Healthcare facilities may consider annual screening for certain high-risk groups, such as pulmonologists or respiratory therapists, or in settings where TB transmission has occurred in the past[4].

High-Risk Individuals

More frequent testing may be recommended for:

- People who have been in close contact with someone who has active TB

- Those with weakened immune systems or HIV infections

- Individuals who have traveled to countries where TB is common

- People working in high-risk settings like correctional facilities, homeless shelters, or certain healthcare environments[1][2]

Post-Exposure Testing

- After a known exposure to TB, immediate testing is recommended, followed by a repeat test 8-10 weeks after the last known exposure[4].

Annual Education and Symptom Screening

While annual testing may not be necessary, the CDC recommends:

- Annual TB education for healthcare personnel[3][4]

- Annual symptom screening for those previously diagnosed with latent TB infection who declined treatment[3]

It's important to note that specific requirements may vary by state, employer, or healthcare facility. Always follow the guidelines set by your local health department or employer regarding TB testing frequency.

[1] https://www.cdc.gov/tb/testing/index.html

[2] https://www.who.int/news-room/questions-and-answers/item/systematic-screening-for-tb

[3] https://www.cdc.gov/tb-healthcare-settings/hcp/screening-testing/baseline-testing.html

[4] https://www.montgomerycountypa.gov/1136/Tuberculosis-TB-Screening-Testing-Treatm

[5] https://medlineplus.gov/lab-tests/tuberculosis-screening/

[6] https://www.urmc.rochester.edu/encyclopedia/content.aspx?contentid=tb_screen_blood&contenttypeid=167

[7] https://www.ncbi.nlm.nih.gov/books/NBK448205/

[8] https://www.dshs.texas.gov/tuberculosis-tb/frequently-asked-questions

The validity of a tuberculosis (TB) test can vary depending on local regulations and the purpose for which it’s required. 

• Healthcare and Employment Requirements: TB test results are often considered valid for 1 year for healthcare workers or employment purposes, though some employers might require more frequent testing based on exposure risk.

• Immigration and Travel: Some immigration or travel requirements also set a 6–12 month validity for a TB test, particularly if the person is entering a high-risk environment.

Always check specific guidelines for the institution or region requesting the test, as they may have their own validity requirements.