What is Tuberculosis or TB infection?
Tuberculosis is an infectious and dangerous disease that affects the lungs. The cause of this infection is bacteria. The transmission agent of this disease is particles that are released by the patient while sneezing and coughing. In developed countries, the prevalence of tuberculosis due to the emergence of HIV has increased. Being infected with HIV causes the body to be unable to resist tuberculosis. Although the prevalence of tuberculosis in the United States is not so severe, tuberculosis is still a serious concern.
Tuberculosis is latent or active. When the disease is latent, TB germ is present in the body, but there are no symptoms, and the so-called disease is inactive. Symptoms appear when TB is activated, and the patient can spread the bacteria to other people.
What are the symptoms of tuberculosis?
- Coughing that may last for three weeks or more.
- Coughing with blood
- Chest pain
- Severe and involuntary weight loss
- Night sweats
- Loss of appetite
Testing for TB Infection
There are two tests for TB infection
- TB blood test
- TB skin test
TB skin test 2 step
This test is also called Mantoux tuberculin skin. You must visit your health care provider twice to take this test. In the first visit, the test is placed on your skin, and in the second visit, the results are read.
How to do TB skin test?
This test is usually well tolerated, and people rarely react negatively to it. The steps of the test are:
- A small amount of purified protein derivative (PPD) solution is first injected into your skin in the lower arm. The PPD solution contains inactivated TB bacteria. After receiving the injection, a small bump will form at the injection site. So there is no need to worry.
- Then you should go to your home and return to the office after 48 to 72 hours to check the reaction on your arm. Keep in mind that if you wait more than 72 hours, you will need to have a new injection.
- The reaction at the injection site indicates whether or not you have TB. The test result will depend on the size, hard area, or swelling at the injection site.
How is the TB skin test result interpreted?
- Positive skin test: This result indicates that your body is infected with TB. In these cases, more tests should be done to determine if the infection is latent or active.
- Negative skin test: This result indicates that your body has not responded to the test. Therefore, the possibility of having active or latent tuberculosis is unlikely.
- False-negative results: In some cases, the test result may be a false negative. False-negative results show that you do not have TB infection, but in fact, you have the disease. This result is due to the weakening of a person’s immune response to TB over time. So if the result of the first test is negative, the second test can be done one to three weeks later. In this way, the body can react positively if it has already been exposed to tuberculosis. If the second TB skin test is still negative, then the result can be considered true. But if the result is positive, other tests will be necessary.
Based on the reaction site, TB skin results can be interpreted as follow:
- Less than 5 mm: Negative
- At least 5 mm: If you have a disease such as HIV, or are taking immunosuppressive medications, or have had TB before, the results are positive.
- At least 10 mm: If you are in high-risk environments, use injectable medications, or are less than four years old, the result is positive.
- 15 mm or higher: Positive
Causes of False-positive result are:
- You have previously received the Calmette-Guérin bacillus (BCG) vaccine
- The test administration was incorrect
- Interpretation of results is not done correctly
- There is a possibility of infection with nontuberculous mycobacteria
Causes of the false-negative result are:
- Incorrect administration and misinterpretation
- Certain immune system conditions, such as an organ transplant
What if the test results are positive?
If the TB test is positive, there is no need to worry because the infection is treatable. In this case, you should do diagnostic tests such as a chest X-ray. It determines whether the infection is active or latent. In some cases, a CT scan may also be performed because this imaging technique reveals more details.
Who needs a TB skin test?
- Anyone who has spent time with the person who suffered from TB infection
- People who are suffering from any immune system problems such as HIV infection
- People from countries where TB infection is prevalent, such as Latin America, Russia, the Caribbean, Asia, Africa, and Eastern Europe, etc.
- People with TB infection symptoms including fever, cough, weight loss, and night sweats.
- People who are in rehabilitation centers or correctional institutes
Where to get a TB test in Las Vegas?
For a TB skin test in Las Vegas, you can go to the Southern Nevada Occupational Health Center (SNOHC). To get acquainted with our services, you can see the top of the website. SNOHC, with more than ten years of experience, tries to promote occupational health for employees and employers.
Frequently Asked Questions about TB Skin Test
What does a positive TB skin test look like?
Based on the reaction site and patient conditions, TB skin results can be interpreted.
- Less than 5 mm: Negative
- 15 mm or higher: Positive
Does a skin test for TB hurt?
No. This is a quick test that does not harm the person.
What happens if you test positive for tuberculosis?
If the test is positive, you should have other diagnostic tests, such as an X-ray.