Igra test (interferon

Definition

What is the IGRA test?

Tuberculosis is a disease that is transmitted through sputum splash (droplet) infected with bacteria Mycobacterium tuberculosis . People who are suspected of having this bacterial infection are advised to do some TB tests.

One of the tests performed to diagnose TB disease is a blood test called a interferon gamma release assay , or commonly abbreviated as IGRA. The IGRA test is a blood test that is done to see the presence of tuberculosis-causing bacteria in a person's body. IGRA is a follow-up examination that is usually carried out after the doctor recognizes the signs that are suspected of being typical of TB.

As the name implies, the IGRA test aims to check for interferon-gamma (IFN-g) in the body. Interferon-gamma (IFN-g) is a protein the body produces when infected with bacteria M. tuberculosis.

Reporting from the CDC, the IGRA test shows that the white blood cells of a person infected with tuberculosis bacteria will release interferon-gamma (IFN-g) when mixed with antigens. Antigen itself is a compound that produces an immune response to fight bacterial infection.

If IFN-g is detected through this test, it means that the tuberculosis germs are in your body.

Before undergoing the IGRA test, the doctor will take a sample of your blood, which is then mixed with antigens and other compounds.

Currently, there are 2 types of IGRA tests that meet the standards U.S. Food and Drug Administration (FDA), namely:

• QuantiFERON®-TB Gold In-Tube (QFT-GIT) test;
• T-SPOT®.TB (T-Spot) test

However, IGRA is only intended for what is bacteria M. tuberculosis is in the body or not. IGRA can't tell whether you have latent TB or active TB disease.

When should I have this test?

The IGRA test is a TB diagnostic method that anyone can follow. In the TB examination stage, this test is performed as a follow-up examination after the doctor has performed a physical examination.

However, of course there are several factors or conditions that require you to undergo IGRA. If you have risk factors related to the possibility of TB transmission, it is best if you seek a hospital or health service center that provides IGRA testing as soon as possible. Some of these risk factors include:

• You are in close contact with people with active TB.
• You live in a country with a high incidence of TB, such as countries in Southeast Asia, Africa and South America.
• You work or live in a home, clinic, hospital, prison, or shelter. Especially if these places are filled with active TB sufferers.
• You have a disease that affects your body's immune system, such as people with HIV / AIDS who need to be checked for TB.

The IGRA test is useful for checking people who are included in the group of people who are at risk for having factors that cause TB. The group could be because they have a disease that weakens the immune system, it could also be because they live near people who are part of the group with risk factors.

In addition, if you have clear signs and symptoms of TB, such as persistent cough, phlegm appearing sometimes accompanied by blood, fever, chills, night sweats, and sudden weight loss, you should immediately undergo this test.

Children under 5 years of age should not undergo IGRA. To diagnose TB in children under 5 years, it is best to use the TB skin test (Mantoux test).

Although more expensive than the Mantoux test, IGRA can be used as an alternative test for TB.

Precautions and warnings

What should I know before taking the IGRA test?

As previously explained, the IGRA test can only show whether you have TB bacteria in your body or not. However, you can't tell if the bacteria are latent or active.

Therefore, when the test results come out, your doctor may ask you to undergo some additional tests. This will depend on the test results as well as your health condition.

In addition, if you have received TB or BCG vaccination, you can still undergo this IGRA test, especially if you have risk factors for TB. This is because someone who has received vaccinations is still at risk of developing latent and active TB infection.

The results of the Mantoux test will usually be affected by the last time you received the BCG vaccine for TB. However, the IGRA test will not be affected by the TB vaccination you have had, even in the near future.

However, if you have been vaccinated against a disease caused by a virus, it is a good idea to wait 4-6 weeks before undergoing IGRA. However, until now there has been no research showing that vaccination against viral diseases can affect the results of the IGRA test. As a preventive measure, you should wait first.

Advantages of the IGRA test

Following are the advantages of undergoing IGRA:

• IGRA results are available within 24 hours
• It only takes one visit to do the test
• The IGRA test will not affect the results of other tests that you will have afterward
• The test results will not be affected by previous TB vaccinations

Drawbacks of the IGRA test

Like other diagnostic methods, IGRA also has several limitations, such as:

• Blood samples should be processed immediately within 8-30 hours of collection, while the white blood cells are still alive
• Errors in taking or moving blood samples can affect the accuracy of the IGRA
• This test cannot detect whether a person has latent or active TB
• This test cannot detect whether a person with latent TB will develop active TB in the future
• Children with TB who are 5 years of age and under are not recommended to undergo this test
• In some places, these tests are still not available and are relatively expensive

Process

What should I do before taking this test?

This test is very simple and fast, you don't need to do any special preparations. Before you decide to undergo the IGRA 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 TB and had previous treatment.

In addition, the doctor may also ask if you are suffering from chronic inflammatory disease. According to a study from Rheumatology International , it is possible that chronic inflammatory disease could affect the test results. Some of the factors that could potentially cause inaccurate test results are low lymphocyte levels and high doses of corticosteroid treatment.

Not only that, you also need to tell whether you have recently received a vaccine for a viral disease in the past one month. This is important because viral vaccination has the potential to cause the IGRA test to show false results.

How is the IGRA test process?

The IGRA test is included in the method of diagnosis which is actually quite easy to do. Make sure you undergo the test at a trusted laboratory or health center, so that the results you will be given are free of mistakes.

1. The process of drawing blood

Like any blood test, this test is done by taking a blood sample from a vein in your arm. Your doctor or medical practitioner will look for the point where your blood vessels are closest to the surface of the skin.

2. Laboratory examination process

As previously explained, the IGRA test works by measuring the body's immune system reaction to bacteria M. tuberculosis . The blood sample that has been taken will be mixed with an antigen from bacteria M. tuberculosis.

The two types of IGRA tests currently available have different types of antigens, test methods, and readings. If the T-Spot test must be processed within 8-30 hours, the QFT-GIT test must not exceed 16 hours to be examined in the laboratory.

Meanwhile, another difference in the two tests is the type of antigen. In the QFT-GIT test, the antigen used is a mixture of synthetic peptides from the type antigen ESAT-6, CFP-10, and TB7.7. The T-Spot test uses a synthetic peptide mixture of ESAT-6 and CFP-10 alone.

There is also a slight difference in laboratory testing techniques between these two tests. The QFT-GIT test measures the concentration or levels of interferon-gamma (IFN-g), while the T-Spot test counts the number of white blood cells that produce IFN-g.

What should I do after undergoing the IGRA test?

Blood draw tests usually will not cause significant side effects because the blood is drawn is also very little. You can return to your normal activities right after the test.

However, in rare cases, some people may feel dizzy and weak after having a blood sample taken. In addition, bruising or swelling may appear at the injection site. You don't need to worry, because these bruises are harmless and can disappear on their own in a matter of days.

IGRA test results will be available within 24 hours after your blood is drawn. Depending on the test results, your doctor may ask you to perform other tests and explain why they are needed.

If you do find a positive test result, 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.

In addition, the doctor will also look for white patches. The spots indicate that your immune system is reacting and fighting the bacteria that enter your body.

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.

Your doctor may also order a test for the sputum or mucus that is produced when you cough. These various examination results can later help your doctor prescribe the right TB medication for you.

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

Explanation of Test Results

What do my IGRA results mean?

The IGRA test results show the number of gamma interferon (IFN-g) produced by white blood cells, or the number of white blood cells that produce IFN-g. Both types of tests have the same reading method, namely positive, negative, and indeterminate .

A positive test result indicates that you have been infected with bacteria M. tuberculosis . If you get a negative result, it means that your body has not been exposed to bacteria M. tuberculosis .

However, there is also a chance that you may get test results indeterminate . This means that the IGRA test cannot determine whether you have an infection or not. Result indeterminate usually caused by disruption of the body's immune system.

The IGRA test is part of the TB disease screening series. However, the IGRA test results do not stand alone to determine a diagnosis of TB in a person. You will need to undergo other tests or laboratory tests such as a smear test so that your doctor can get a more specific and definite diagnosis.

Hello Health Group does not provide medical advice, diagnosis or treatment.