How is Tuberculosis Testing performed?

 Tuberculosis or TB can be deadly and highly contagious. As a result, TB testing and screening are critical for public health. If you experience symptoms, are at a high risk of developing active TB, or are exposed to infection, you should visit a diagnostics center in Nashville for TB testing. This blog will discuss the types of TB testing.

Types of Tuberculosis Testing

Tuberculosis testing is of two types – skin test and blood test. Let’s discuss them further.

TB Skin Test

It is also called the PPD test, tuberculin test, or Mantoux test. During the test, your healthcare provider will inject a small amount of fluid containing certain TB bacterium components under your skin. It will cause your immune system to cause a skin reaction upon identifying the injected fluid as a threat.

Your physician will determine whether you have TB based on the skin's response. Even if you have a positive test result, your healthcare provider may perform further tests to diagnose whether you have a latent or active infection.

The following people are at a higher risk of getting infected with TB bacteria-

• People spending time with an infected patient

• Individuals living or working in high-risk settings, such as hospitals, homeless shelters, etc.

• Healthcare workers caring for patients with a high risk of TB

• Infants, children, and teens exposed to adults with increased risk of TB

It is the most common test used to diagnose suspected active TB. Besides, it is the preferred test for children below 5.

Test results can sometimes show false positive or false negative results.

False Positive result – It wrongly indicates that you have TB, while the reality is the opposite. Possible causes can be – 

• Incorrect measurement or interpretation of reaction

• Infection with non-tuberculosis mycobacteria

• Previous TB vaccine bacille calmette-guérin or BCG

• Not using the right antigen during the test

False Negative result – It wrongly indicates you do not have TB, whereas, in reality, you are infected. Possible causes are –

• Recent infection in the last 8 to 10 weeks

• Children younger than 6 months

• Recent live virus measles or smallpox vaccination

• Absence of normal immune response to specific antigen or allergen

• Incorrect measuring or interpretation of the skin reaction to the test

TB Blood Test

It is also called interferon-gamma release assays or IGRAs. FDA has approved two TB blood tests – QFT-Plus and the T-spot.

Your healthcare provider may suggest a TB blood test if you have received the TB vaccine BCG. They will draw your blood and send it for further laboratory analysis. If the test result came positive, it implies you are infected with TB bacteria. In such cases, they will perform additional tests to determine whether you have a latent or active TB infection.

Tuberculosis Skin Testing Procedure

Before the test, your healthcare professional at a medical clinic in Nashville will consider your medical history to determine whether you are suited to take the test. They may ask whether you have taken the test in the past and experienced any negative reaction to it.

During the test, your healthcare provider will inject 0.1 ml of tuberculin purified protein derivative (also called PPD or tuberculin) under your forearm skin. Next, they will use the mm ruler to measure the weal – the pale skin elevation. It will help them determine whether they have successfully administered the skin test. If the weal is less than 6 mm, your physician might need to administer the test again.

Ideally, you should book the follow-up appointment for test result interpretation within 48-72 hours of getting tested. If you miss this appointment, you may need to get the test redone. In addition, you should avoid scratching or rubbing the test site and keep it uncovered.

Managing side effects

Usually, TB skin tests do not cause any side effects. However, some people might experience a negative reaction. It includes –

• Mild itching

• Swelling

• Irritation

These are temporary symptoms that disappear in one or two weeks. A few people may also experience severe symptoms, such as severe allergic reactions, blistering, shortness of breath, fever, lightheadedness, etc. If you experience these symptoms, visit your healthcare provider immediately. 

If you experience symptoms or are at a high risk of developing active TB, visit a family clinic Nashville for Tuberculosis testing. Early diagnosis will help get early treatment for proper recovery.