Did you feel a little scared when the doctor told someone you know to "take a TB test"? Or do you wonder what would happen if you had to take this test yourself? Many of us are actually scared when we hear the word 'TB'. But if we are fully informed about this test and this disease, we can eliminate this unnecessary fear. So today, let's talk about what this TB test is, how it is done, and what happens when the results come back, in a very simple way that you can understand.
Simply put, what is a TB test?
It's very simple. A TB test checks to see if you have the bacteria that causes tuberculosis, called Mycobacterium tuberculosis , in your body.
There are two main ways to perform this test.
1. Skin test: This is also called the Mantoux test .
2. Blood test: This is called an Interferon-Gamma Release Assay (IGRA) .
The skin test is most commonly done on children under the age of 5. However, these days, especially for healthcare workers, those with weakened immune systems, or those taking medications that suppress immunity, this blood test is also often done.
The important thing is that both of these tests can only tell you if you have TB germs in your body. They cannot tell you for sure whether you have active TB disease or if the germs are dormant (latent/dormant) in your body. To find out, you will need to do other tests, such as a sputum test .
Who wants to take this test?
Your doctor may recommend this test if you have symptoms of tuberculosis or if you are at high risk of developing tuberculosis. Some workplaces, such as hospitals and childcare centers, may also require you to have this test before you start work.
You may be at higher risk of developing TB if you:
- If you are a healthcare worker who interacts with patients.
- If you live or work in a place where tuberculosis is common (e.g. crowded places such as nursing homes, prisons).
- If you have had contact with someone with active tuberculosis .
- If you have a medical condition that weakens your immune system , or if you are taking medication that does so.
- If you have recently traveled to a country where tuberculosis is common (such as some countries in Asia or Africa), it is very important to tell your doctor about this trip.
If you think you are at risk for this, be sure to talk to your doctor about it.
How is the TB test actually done?
Both types of tests work on the same principle. That is, they measure your immune system's response to antigens from the TB bacteria. Simply put, an antigen is something foreign to our body. When it enters the body, our immune system starts to fight against it. This fight is what we measure with this test.
Mantoux test
For this test, you will have to see the doctor twice within two to three days.
- On the first day:
- A doctor or nurse will clean the skin on the inside of your arm, below the elbow, and then inject a small amount of liquid under the skin with a very small needle. This liquid is called PPD (purified protein derivative) .
- Don't worry, there are no live bacteria in this. It won't make you sick.
- A small bubble will appear at the injection site. It will disappear in a few hours. Sometimes I circle the area with a pen to make it easier to see after a couple of days.
- On the second day (between 48 and 72 hours):
- You need to go see the doctor again. He will check if there is any skin reaction where the injection was given.
- If you have been infected with the TB germ before, the area may be red, slightly swollen, and swollen enough to hold your hand .
- It is mandatory to go for this second test. If you don't go within 72 hours, you will have to take the test again from the beginning because the results cannot be given accurately.
Blood test (IGRA Test)
This is just like donating blood normally. Very quick.
- A nurse will find an easy vein to draw blood from on the inside of your elbow.
- The area is cleaned, a small needle is inserted, and a little blood is collected in a tube. You will feel a slight pain when the needle is inserted.
- After the blood is drawn, the needle is removed, the area is pressed with a piece of cotton, and a plaster is applied.
- The whole thing doesn't take more than five minutes.
- Your blood sample is then sent to a laboratory. It is mixed with TB antigens and tested to see if your cells release a protein called interferon-gamma . Your doctor will tell you about the results when they come back.
How to understand the results?
The result of a test can be either "Negative" or "Positive" .
- Negative result:
- This means that your body has not shown any response to the TB germ. This means that the TB germ has most likely not entered your body.
- However, if you have symptoms of TB, the doctor may still do more tests, even if the result is negative.
- Positive result:
- This means that your body has responded to the TB germ. That means that at some point in your life, the TB germ has entered your body.
- Sometimes, the BCG vaccine we received as children can cause a false-positive result in a skin test.
Remember this! Don't be afraid of a positive test. It doesn't mean you have active tuberculosis. It just means the germ has entered your body.
| How does a skin test become "positive"? | |
|---|---|
| The size of the skin thickening and swelling (in millimeters) | Who is considered "positive"? |
| If 5 mm or more | People with very weak immune systems (e.g., HIV-infected people, organ transplant recipients, people taking steroids for long periods of time) |
| If 10 mm or more | Healthcare workers, people who have recently returned from a country where TB is common, young children, and people with other illnesses such as diabetes. |
| If 15 mm or more | Anyone who has no risk factors for tuberculosis. |
If the test is positive, what happens next?
If the test is positive, your doctor will do several more tests to confirm whether you have an active disease.
- Chest X-ray: To check for any changes in the lungs.
- Sputum Test: Checks for TB bacteria in your sputum.
After these tests, the doctor will determine whether you have a latent or active condition and begin appropriate treatment. There are treatments for both conditions.
When you should see a doctor
If you have symptoms related to tuberculosis, or if you think you may have been exposed to someone with TB, see a doctor as soon as possible.
Be aware of symptoms like these:
- Cough that lasts more than two weeks
- Chest pain
- Weight loss for no reason
- A slight fever that comes in the evening
- Night sweats
Tuberculosis can be fatal if not treated properly. But the good news is that if you take the medicine prescribed by your doctor for the prescribed period, you can completely cure tuberculosis . So, don't panic, and if you have any doubts, the best thing to do is to seek medical advice.
Take-Home Message
- A TB test only checks whether you have ever been exposed to the TB germ. It cannot tell if you have active disease.
- There are two main types of tests: the skin test (Mantoux) and the blood test (IGRA).
- Don't panic if a test result is "positive." Your doctor will do further testing to determine if you need treatment, and if so, what type.
- Tuberculosis is now a completely curable disease. The most important thing is to follow the doctor's instructions and medication as prescribed.
- If you have symptoms of TB or are in a risk group, never delay getting tested. See your doctor right away.
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