what tb skin test that is positive

2 min read 17-12-2024

A positive tuberculosis (TB) skin test, also known as a Mantoux tuberculin skin test (TST) or PPD (purified protein derivative) test, doesn't automatically mean you have active TB disease. It indicates you've been infected with the Mycobacterium tuberculosis bacteria at some point in your life. This infection can be latent (inactive) or progress to active TB disease. Understanding the difference is crucial.

Understanding Latent TB Infection (LTBI)

A positive TB skin test often signifies latent TB infection (LTBI). This means the bacteria are present in your body, but they're not actively causing illness. You're not contagious and generally don't experience symptoms. However, LTBI can reactivate into active TB disease later in life, especially if your immune system weakens.

Factors Affecting Reactivation

Several factors increase the risk of LTBI reactivating into active TB:

Weakened immune system: HIV/AIDS, certain cancers, diabetes, and other conditions can compromise the immune system, increasing the risk of reactivation.
Age: Older individuals are at higher risk.
Certain medications: Some medications, like corticosteroids, suppress the immune system.
Substance abuse: Alcohol and drug abuse can weaken the immune system.
Underlying health conditions: Severe malnutrition or chronic kidney disease can also increase risk.

What a Positive Test Doesn't Mean

It's important to reiterate that a positive TB skin test doesn't automatically diagnose active TB disease. Further testing is always necessary to confirm an active infection.

What Happens After a Positive TB Skin Test?

If your TB skin test is positive, your doctor will likely order additional tests, including:

Chest X-ray: This helps to visualize your lungs and check for any signs of active TB disease.
Sputum culture: This involves collecting a sample of your sputum (phlegm) to test for the presence of M. tuberculosis bacteria. This is the most definitive test for active TB.
Blood tests: These tests can help detect active TB infection and assess your immune response to the bacteria. An Interferon-gamma release assay (IGRA) blood test is an alternative to the skin test.

Treatment for Latent TB Infection

If you have a positive TB skin test but no signs of active disease, your doctor might recommend treatment for LTBI. This usually involves taking antibiotics for several months to prevent the infection from becoming active. This preventative treatment is crucial in minimizing the risk of developing active TB in the future.

Active TB Disease: A Serious Concern

Active TB disease is a serious illness that requires immediate medical attention. Symptoms can include:

Persistent cough (often with blood)
Fever
Night sweats
Weight loss
Fatigue
Chest pain

If you experience any of these symptoms after a positive TB skin test, contact your doctor immediately.

Prevention and Control

Preventive measures to reduce the spread of TB are essential. These include:

Vaccination: The BCG vaccine is used in many countries to protect against TB, although its effectiveness varies.
Early detection and treatment: Regular screenings and prompt treatment of latent TB infection are vital.
Infection control: Proper ventilation and hygiene practices help to minimize transmission.

Conclusion

A positive TB skin test is a serious matter requiring further evaluation. While it doesn't automatically diagnose active TB, it signifies exposure to the bacteria and warrants additional testing to rule out active disease or initiate treatment for latent TB infection. Early detection and prompt treatment are crucial in preventing the development of active TB disease and protecting your health. Remember to consult your doctor for proper diagnosis and management.