how can you tell if your tb test is positive

3 min read 17-12-2024

how can you tell if your tb test is positive

A positive tuberculosis (TB) skin test, also known as a Mantoux tuberculin skin test (TST), doesn't automatically mean you have active TB disease. It indicates you've been infected with the bacteria that causes TB, Mycobacterium tuberculosis. This infection can remain latent (dormant) for years, without causing illness. Understanding how to interpret your TB test results is crucial. This article will explain how to tell if your TB test is positive and what steps to take next.

Understanding the TB Skin Test

The TB skin test involves a small injection of tuberculin under the skin of your forearm. You'll return 48-72 hours later for a healthcare professional to check the injection site. The test measures the size of any reaction (induration – a raised, hard area), not redness. This reaction indicates your immune system's response to the bacteria.

Interpreting the Results: What's Considered Positive?

The interpretation of a positive TB skin test depends on several factors, including your risk factors for TB and your overall health. A healthcare professional will consider these factors when evaluating your test. Generally, a positive result is defined as:

For most people: An induration of 15 millimeters (mm) or more in diameter.
For people with increased risk factors: An induration of 10 mm or more. This includes those with:
- Weakened immune systems (HIV, cancer, etc.)
- Recent close contact with someone with active TB
- Those who use drugs that suppress the immune system
- People with certain medical conditions, like diabetes
For people at high risk: An induration of 5 mm or more. This group includes those with:
- HIV infection with a CD4 count less than 200 cells/mm³
- Organ transplant recipients
- Individuals with severe immune deficiency

Important Note: A healthcare professional will interpret your test. Don't try to self-diagnose based solely on measurement. They'll consider your medical history and risk factors to determine the next steps.

What Happens if My TB Test is Positive?

A positive TB skin test means you need further testing to determine if you have latent TB infection (LTBI) or active TB disease. Active TB is contagious and requires treatment. LTBI isn't contagious but can progress to active TB if left untreated.

Further Testing for Confirmation

Your doctor will likely order one or more of the following tests:

Chest X-ray: To check for any abnormalities in your lungs.
Sputum test: A sample of your phlegm is examined for the presence of TB bacteria. This is crucial for diagnosing active TB.
Blood tests: To help assess your immune response and detect active TB. An interferon-gamma release assay (IGRA) blood test is another option for TB testing, which doesn't rely on prior BCG vaccination.

What to Do if You Have a Positive TB Test

If your TB test is positive, don't panic. Follow your healthcare provider's instructions carefully. They will recommend the appropriate treatment based on your diagnosis (LTBI or active TB). Treatment for LTBI typically involves taking antibiotics for several months. Treatment for active TB requires a longer course of medication, often involving multiple drugs.

Preventing the Spread of TB

If you're diagnosed with active TB, it's crucial to follow your doctor's instructions diligently to prevent spreading the disease to others. This might involve staying home while contagious, following prescribed medication, and taking steps to improve your immune system.

Conclusion

A positive TB test requires further evaluation by a healthcare professional. Understanding the interpretation of your test results and taking the necessary steps to determine whether you have latent TB infection or active TB disease is critical for your health and the health of those around you. Don't hesitate to contact your doctor if you have any questions or concerns about your TB test results. Early diagnosis and treatment are key to preventing serious health complications.