What is tuberculosis (TB) screening test?
A TB screening test determines if you are infected with the bacteria that cause tuberculosis (known as Mycobacterium tuberculosis). A bacterial illness called tuberculosis mostly affects the lungs. However, it can also have an impact on the kidneys, spine, and brain, among other body parts. When a TB-infected person sneezes or coughs, TB can transfer from one person to another.
TB bacteria can induce two different conditions:
Latent TB infection
When you have a latent TB infection, your body still harbors active TB bacteria, but you are otherwise healthy. You don't exhibit any symptoms and cannot infect others with the illness. However, the germs can begin to spread and infect you later. The goal of treating latent TB infection is to keep you from developing active TB disease.
Active TB disease
When you have an active TB illness, your body's TB bacteria are actively developing there and making you ill. You can infect others with TB if the bacteria multiply in your throat or lungs. Antibiotics work to treat TB illness. However, if left untreated, it may result in serious disease.
A TB screening test determines if you are infected with TB bacteria. However, it cannot determine if you have an active or latent TB infection. You'll need further tests to determine which form of TB you have if a TB screening test reveals TB bacteria, so you can receive the proper treatment.
A TB skin test and a TB blood test are the two types of TB tests that are utilized for screening. Which test is best for you might be determined by your doctor.
Other names: Other names of this test are TB skin test, TB test, latent TB infection test, purified protein derivative (PPD) test, Mantoux tuberculin skin test; IGRA test, TB blood test
What is the use of a TB test?
When someone has been exposed to a person who has active TB illness or when there is a significant risk of exposure, TB screening is done to test for symptoms of TB bacteria. It does not indicate if you are suffering from an active or latent ailment.
What is the need of a TB test?
In case you get exposed to someone who has an active TB illness or you are at high risk of getting it, you would require a TB skin test or TB blood test.
You are at increased chance of exposure if:
- You are a healthcare worker.
- You work or live in a place where TB is more common.
- You were born in countries or often travel to places where TB disease is common.
You would require a TB screening test if you have symptoms of TB disease such as:
You may require a TB screening test if you have a certain health condition that increases your chances of getting active TB disease. These conditions are:
- Having an organ transplant
- Use of illegal drugs
What happens during a TB test?
A TB screening test can be done in a hospital, health center, or your doctor's office. Depending on the health and medical history, either a TB skin test or a TB blood test will be required.
For skin test
You will require two visits to perform a TB skin test, commonly known as a Mantoux tuberculin skin test. The test is administered at the first appointment, and the findings are reviewed during the second visit.
In the first visit:
- A little amount of fluid will be injected beneath your skin in the bottom portion of your arm using a tiny needle by a medical practitioner. Tuberculin is the name of the fluid. It includes a protein derived from the TB-causing bacterium. You can't get sick from it.
- Your arm will develop a little lump from the fluid.
- The test area will be left uncovered.
- You must refrain from touching or applying lotion to the test area. Getting it wet is OK. You can apply an ice cube or cold cloth on it to relieve itching.
You will come back for a second visit after two to three days. The test location on your arm will be examined by a medical specialist to see how your skin responds. The expert will measure any hard skin bumps if there are any. The significance of the bump depends on its size, your risk of having an active TB illness, and your risk of coming into contact with TB germs. The doctor will inform you whether the bump indicates a likelihood of having TB germs or not.
For blood test
An IGRA test, commonly known as a blood test for tuberculosis, requires a healthcare provider to draw blood using a tiny needle from a vein in your arm. A tiny amount of blood will be collected into a test tube or vial once the needle has been placed. The needle may hurt somewhat when it enters or exits your body. Usually, this only needs a few minutes.
How to prepare for the test?
Both the TB skin test and the TB blood test require no extra preparation on your part.
Does the test include any risks?
A skin or blood test for TB has no risk. Although you can experience a pinch when the fluid is injected beneath your skin for a TB skin test.
For a blood test, you could have a little pain or discomfort where the needle was inserted, but most effects go rapidly.
What do the findings indicate?
The findings of your TB skin or blood test will be positive or negative.
If the test is positive, you have contracted the TB bacterium. To determine whether you have a latent TB infection or TB illness, you will require more testing. Sputum culture and chest x-ray are two examples of these testing. You could get a TB blood test to confirm the outcome if your TB skin test revealed a positive result.
A negative outcome indicates that neither your skin nor your blood responded to the test. It's unlikely that you have a TB illness or a latent infection. But you will require more testing if you:
- Have signs and symptoms of TB.
- Were tested sooner than six to eight weeks after exposure to TB.
- Underwent a TB skin test after being around someone with TB illness,
When a TB blood test result is "borderline," it suggests that it is possible that you may not have a TB infection. If this occurs, you'll probably take the test once again.
The majority of the time, TB screening tests are reliable. However, TB skin tests are less reliable than TB blood testing. Your doctor will take into account any potential effects your medical history may have on the accuracy of your test results.
Consult your doctor if you have any queries regarding your results.
Important information about a TB screening?
Treatment is necessary for both latent and active TB infections. Antibiotics are used as a therapy for both illnesses. You must take your medication as prescribed in order to ensure that all TB bacteria are eliminated from your body. If you stop your medication too soon, the infection can return and become more difficult to cure.