Mantoux test for TBC, procedures, and understand the results

Definition

What is the Mantoux test?

Tuberculosis is an airborne disease caused by a bacterial infection Mycobacterium tuberculosis . People who are suspected of having this bacterial infection are advised to do a diagnostic test for TB.

One of the tests carried out to diagnose TB disease is Mantoux test . This test is done on the skin so it is also known as the TB skin test (tuberculosis skin test / TST).

This test is done by injecting a tuberculin fluid. That is why, this one TB test is also known as the tuberculin test.

The Mantoux test is a common initial screening method for screening or early detection of TB disease in certain populations. According to the Director General of Health Services of the Republic of Indonesia, the Mantoux test or tuberculin test is carried out to determine the possibility of TB-causing bacteria in a person's body.

This test is also very useful for early detection of TB disease for people who are traveling to countries with high TB ​​cases or people who work in health facilities.

When do I need to go on a Mantoux test ?

Mantoux test is a method of diagnosis or examination of TB that can be followed by anyone. However, of course there are several factors that make you have to undergo this test.

If you have any of the factors that put you at risk of contracting TB, it is recommended that you go to a hospital or health care center that provides tuberculin testing as soon as possible:

• Make close enough contact with people with active TB.
• Living in a country with a high incidence of tuberculosis, such as countries in Southeast Asia, Africa and South America.
• Work or live in an institution, clinic, hospital, prison, or shelter where people with active TB are found.

People who have certain diseases that affect the body's immune system, such as HIV / AIDS, rheumatoid arthritis, and diabetes need to be checked for TB immediately.

Precautions & warnings

What should I know before taking the Mantoux test?

As previously explained, the results of the Mantoux test can only show whether you have tuberculosis bacteria in your body or not. However, you cannot tell if the tuberculosis bacteria is latent (not actively infecting or multiplying) or active.

Therefore, when you get the results from the tuberculin test, your doctor may ask you to undergo some additional tests. The type of follow-up test that is done depends on how the test results are and your health condition, such as experiencing a medical condition that is suspected of being a symptom of tuberculosis.

In addition, if you have had the TB vaccination or BCG vaccine, you can still undergo the Mantoux test, especially if you have risk factors for TB. This is because someone who has received vaccinations is still at risk for TB infection, both latent TB and active pulmonary TB.

However, make sure you do not get vaccinated for TB, the BCG vaccine and the Mantoux test, in the near future.

The time between vaccinations and skin tests that are too close together has the potential to result in inaccurate test results. It's a good idea to give yourself about 1 month between vaccinations and the skin test.

The same is true if you have received vaccinations for a disease caused by a virus, such as the smallpox vaccine. You will need to wait at least 4-6 weeks before having the Mantoux test.

Process

What should I do before undergoing a Mantoux test ?

Mantoux test takes place very simply and quickly. You don't need to make special preparations. Before deciding to undergo a TB skin test, there are a number of things you must do first.

First of all, you should tell your doctor or medical team if you have had tuberculosis and had previous TB treatment.

In addition, the doctor will also usually ask if you have had a previous Mantoux test. If so, you need to let them know if there have been any side effects or severe reactions after your test, such as sores, resilience, or anaphylactic shock.

Not only that, you also need to tell if you have recently received the BCG vaccine in the past one month. This is very important because the BCG vaccine has the potential to make the Mantoux test false.

How is the Mantoux test process?

The Mantoux test or tuberculin test can seem daunting because it is done by injection. However, this TB skin test is actually quite easy to do. The Mantoux test will usually be done in two stages.

First, the doctor will inject a small amount of a sterile solution, which contains tuberculin. Tuberculin is a fraction of the pure protein that comes from Mycobacterium tuberculosis . If a person is infected with TB, their immune system will react to the tuberculin fluid that is injected.

The injection is usually done in the inner forearm. When the Mantoux test is done correctly, the injection point will form a small lump on the skin, but not the redness that appears as a result of the injection. This lump is called an induration.

The second stage TB skin test should be done between 48-72 hours after the first tuberculin injection is done. The doctor will check to see what is happening to the skin and how the body responds to it.

In the second stage of the Mantoux test, the doctor will measure the diameter of the indurated lump on the forearm in the same direction as the length of the hand. The size of the induration is usually recorded in millimeters. After that, the doctor asks several questions to confirm your health condition.

What should I do after taking the Mantoux test?

You can return to your normal activities right after the TB skin test is done. However, there are a number of things that you should pay attention to, namely:

• Avoid scratching or rubbing the tuberculin injection site.
• Leave the injection site open, do not cover it with bandages, bandages, or apply ointment.
• If it appears resilient at the injection site which causes discomfort, you can apply cold water to it.

Mantoux test is a safe test and rarely causes serious side effects. If side effects occur, you may experience swelling, redness, resilience, and itching. The side effects only last for a while.

Follow-up tests may be needed after obtaining the tuberculin test results. The doctor will explain the reasons and what further examination methods are needed.

If you find that you have a positive Mantoux test, your doctor may order an X-ray or chest X-ray. By doing a chest x-ray, your doctor can see if you have latent TB infection or active TB disease by looking at the condition of your lungs.

As an alternative to a chest X-ray, your doctor will recommend that you undergo a CT scan. This is because the results of the images produced from the CT scan look more detailed and clear.

If the results of the chest X-ray imaging test show active TB, your doctor may also order a laboratory test (smear) that takes a sample of your sputum or mucus.

Explanation of the test results

What do my Mantoux test results mean?

After 2-3 days, the results of the Mantoux test or tuberculin test can show your chances of contracting TB disease.

If the test site or the injection site is only reddish without an induration or lump, you may be negative or not infected with TB bacteria.

Conversely, if you have red bumps, it is likely that you have been infected with tuberculosis bacteria.

According to the CDC, the Mantoux readout test can be interpreted or classified as a positive tuberculin reaction under the following conditions.

1. The size of the induration> 5 mm, this applies to patients with conditions:

• Are HIV positive.
• Come into contact with someone who has active tuberculosis.
• Have had tuberculosis and have been declared cured
• An organ transplant recipient who has received immunosuppressant drugs, such as cyclophosphamide or methotrexate.
• Patients on long-term (more than six weeks) systemic corticosteroid therapy and those taking prednisone doses before 15 mg / day or equivalent.
• End-stage kidney disease.

2. The size of the induration> 10 mm, this applies to people who are:

• People living in countries with high TB ​​cases, including Indonesia.
• Injecting drug users.
• Population in high-risk places (eg prisons, nursing homes, hospitals, homeless shelters).
• Lab staff with tuberculosis patients.
• People with clinical conditions that put them at high risk (eg, diabetes, long-term corticosteroid therapy, leukemia, end-stage kidney disease, chronic malabsorption syndrome, low body weight).
• Children under four years of age, or children and adolescents who are exposed to adults in high-risk categories.
• Infants, children and adolescents who are exposed to adults are in high risk categories.

3. The size of the induration> 15 mm, this applies to patients with conditions:

People without known risk factors for TB. Reactions greater than 15 mm are unlikely to be caused by previous BCG vaccination or environmental exposure.

It is important to know, the Mantoux test does not measure the level of immunity to TB disease, but the level of a person's hypersensitivity to TB infection. The results of the Mantoux test with tuberculin also have a low sensitivity compared to other TB diagnosis methods, so the test results are not one hundred percent accurate.

Some people may get false or false test results because they have several factors that influence the test results. Here are some of the possibilities the Mantoux test could bring up false results.

The Mantoux test is false positive

Some people may react to this test even if they are not infected with bacteria M. tuberculosis . The causes of this false positive reaction can include the following:

• The presence of non-tuberculous mycobacteria infection in the body.
• Have had a previous BCG vaccination.
• Incorrect Mantoux test method.
• Interpretation of incorrect tuberculin reactions such as measuring errors or reading of induration measurements.
• Using the wrong size antigen bottle.

In people who have a low risk of exposure to the TB bacteria, a positive result is most likely a false positive.

A false positive result could be due to the presence of a nontuberculosis mycobacteria or previous BCG vaccine. Vaccinations before BCG can produce false positive results for years to come.

A positive tuberculin test does not mean you have an infectious (active) infection. As noted, the tuberculin test cannot show if the infection is active or inactive (latent TB).

The Mantoux test is false-negative

A negative Mantoux test result usually indicates that the individual has never been exposed M. tuberculosis . However, there are several factors that can cause a false negative result, namely:

• Having skin anergy (anergy is the inability to react to a skin test due to a weak immune system).
• Recently infected with tuberculosis (within 8-10 weeks of exposure).
• Infected with tuberculosis that has been very long (chronic).
• Very young (less than six months).
• Get vaccinated against viruses (such as measles and smallpox).
• Have extra pulmonary TB disease.
• Have some viral illnesses (for example, measles and chickenpox)
• Undergoing the wrong tuberculin test procedure, such as the interpretation of the wrong reaction, inadequate dosage, and accidental injection of other drugs.

If you have any questions related to the Mantoux test process, please consult your doctor for a better understanding.