TB Testing

A tuberculosis (TB) test is a diagnostic tool used to determine whether a person has been infected with Mycobacterium tuberculosis, the bacterium that causes TB. The test helps identify latent TB infection or active TB disease, guiding appropriate treatment and prevention measures.

What is it?

A TB test is used to detect the presence of tuberculosis infection. There are two primary types of TB tests: the tuberculin skin test (TST), also known as the Mantoux test, and the TB blood test, also known as the interferon-gamma release assay (IGRA). Both tests help determine if a person has been infected with TB bacteria.

What happens during the procedure:

The procedure for TB testing varies depending on the type of test used:

Tuberculin Skin Test (TST):

Preparation:
- Inform the healthcare provider of any previous positive TB test results or history of TB infection.
Administering the Test:
- A small amount of purified protein derivative (PPD) is injected just beneath the skin on the inner forearm.
- A small, raised bump (wheal) will form at the injection site.
Monitoring:
- The patient is instructed to return to the healthcare provider after 48-72 hours to have the injection site examined.
Reading the Results:
- The healthcare provider measures the size of the induration (raised, hard area) at the injection site.
- A positive result is indicated by a specific size of induration, depending on the patient’s risk factors and health status.

TB Blood Test (IGRA):

Preparation:
- No special preparation is required.
Sample Collection:
- A healthcare provider draws a blood sample from a vein in the patient’s arm.
Laboratory Analysis:
- The blood sample is sent to a laboratory where it is tested for immune response to TB bacteria.
Waiting for Results:
- Results are usually available within a few days.
Interpreting the Results:
- A positive IGRA result indicates TB infection, while a negative result suggests no infection.

Benefits:

Early Detection: Identifies TB infection early, allowing for timely treatment and prevention of disease spread.
Accurate Diagnosis: Helps distinguish between latent TB infection and active TB disease with further evaluation.
Public Health: Reduces the risk of TB transmission within communities by identifying and treating infected individuals.
Convenient: Blood tests provide a single-visit alternative to skin tests, reducing the need for a follow-up visit.

Things to keep in mind:

False Positives/Negatives: TST can yield false-positive results in individuals vaccinated with Bacille Calmette-Guerin (BCG) and false negatives in immunocompromised patients. IGRA is not affected by BCG vaccination.
Follow-Up: Positive test results require further evaluation, including chest X-rays and sputum tests, to confirm active TB disease.
Symptoms Monitoring: Be aware of TB symptoms such as a persistent cough, night sweats, fever, and weight loss. Seek medical attention if these occur.
Regular Screening: Individuals at high risk for TB infection, such as healthcare workers and those with weakened immune systems, should undergo regular screening.

Alternatives:

Chest X-Ray: Used to detect active TB disease in individuals with a positive TB test.
Sputum Test: Examines sputum samples for the presence of TB bacteria, confirming active TB disease.
CT Scan: Provides detailed imaging of the lungs to detect TB-related abnormalities.
Molecular Tests: Rapid diagnostic tests that detect TB bacteria’s genetic material, useful for confirming active TB disease.

TB Testing

What is it?

What happens during the procedure:

Benefits:

Things to keep in mind:

Alternatives:

Treatments and services

Injuries

Illnesses

Procedures

On-Site Diagnostic Tests

Vaccines/ TB Testing

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