Testing for Tuberculosis (TB) | TB

Tuberculosis (TB) is a disease that is spread through the air from one person to another. When someone who is sick with TB coughs, speaks, laughs, sings, or sneezes, people nearby may breathe TB bacteria into their lungs. TB usually attacks the lungs, but can also attack other parts of the body, such as the brain, spine, or kidneys.

TB bacteria can live in the body without making a person sick. This is called latent TB infection. People with latent TB infection do not feel sick, do not have TB symptoms, and cannot spread TB bacteria to others. Some people with latent TB infection go on to develop TB disease. People with TB disease can spread the bacteria to others, feel sick, and can have symptoms including fever, night sweats, cough, and weight loss.

There are two kinds of tests that are used to determine if a person has been infected with TB bacteria: the tuberculin skin test and TB blood tests.

Tuberculin Skin Test (TST)

What is a TST?

The Mantoux tuberculin skin test is a test to check if a person has been infected with TB bacteria.

How does the TST work?

Using a small needle, a health care provider injects a liquid (called tuberculin) into the skin of the lower part of the arm. When injected, a small, pale bump will appear. This is different from a Bacille Calmette-Guerin (BCG) shot (a TB vaccine that many people living outside of the United States receive).

The person given the TST must return within 2 or 3 days to have a trained health care worker look for a reaction on the arm where the liquid was injected. The health care worker will look for a raised, hard area or swelling, and if present, measure its size using a ruler. Redness by itself is not considered part of the reaction.

What does a positive TST result mean?

The TST result depends on the size of the raised, hard area or swelling. It also depends on the person’s risk of being infected with TB bacteria and the progression to TB disease if infected.

• Positive TST: This means the person’s body was infected with TB bacteria. Additional tests are needed to determine if the person has latent TB infection or TB disease. A health care worker will then provide treatment as needed.
• Negative TST: This means the person’s body did not react to the test, and that latent TB infection or TB disease is not likely.

Who can receive a TST?

Almost everyone can receive a TST, including infants, children, pregnant women, people living with HIV, and people who have had a BCG shot. People who had a severe reaction to a previous TST should not receive another TST.

How often can a TST be given?

Usually, there is no problem with repeated TSTs unless a person has had a severe reaction to a previous TST.

Testing for TB in People with a BCG

People who have had a previous BCG shot may receive a TST. In some people, the BCG shot may cause a positive TST when they are not infected with TB bacteria. If a TST is positive, additional tests are needed.

TB Blood Tests

What is an Interferon Gamma Release Assay (IGRA)?

An IGRA is a blood test that can determine if a person has been infected with TB bacteria. An IGRA measures how strong a person’s immune system reacts to TB bacteria by testing the person’s blood in a laboratory. Two IGRAs are approved by the U.S. Food and Drug Administration (FDA) and are available in the United States:

1. QuantiFERON®–TB Gold In-Tube test (QFT–GIT)
2. T–SPOT®.TB test (T–Spot)

How does the IGRA work?

Blood is collected into special tubes using a needle. The blood is delivered to a laboratory as directed by the IGRA test instructions. The laboratory runs the test and reports the results to the health care provider.

What does a positive IGRA result mean?

• Positive IGRA: This means that the person has been infected with TB bacteria. Additional tests are needed to determine if the person has latent TB infection or TB disease. A health care worker will then provide treatment as needed.
• Negative IGRA: This means that the person’s blood did not react to the test and that latent TB infection or TB disease is not likely.

Who can receive an IGRA?

Anyone can have an IGRA in place of a TST. This can be for any situation where a TST is recommended. In general, a person should have either a TST or an IGRA, but not both. There are rare exceptions when results from both tests may be useful in deciding whether a person has been infected with TB. IGRAs are the preferred method of TB infection testing for the following:

• People who have received the BCG shot
• People who have a difficult time returning for a second appointment to look at the TST after the test was given

How often can an IGRA be given?

There is no problem with repeated IGRAs.

Who Should Get Tested for TB?

The Centers for Disease Control and Prevention (CDC) and the United States Preventive Services Task Force (USPSTF) recommend testing populations that are at increased risk for TB infection. Certain people should be tested for TB bacteria because they are more likely to get TB disease, including:

• People who have spent time with someone who has TB disease
• People with HIV infection or another medical problem that weakens the immune system
• People who have symptoms of TB disease (fever, night sweats, cough, and weight loss)
• People from a country where TB disease is common (most countries in Latin America, the Caribbean, Africa, Asia, Eastern Europe, and Russia)
• People who live or work somewhere in the United States where TB disease is more common (homeless shelters, prison or jails, or some nursing homes)
• People who use illegal drugs

Choosing a TB Test

Choosing which TB test to use should be done by the person’s health care provider. Factors in selecting which test to use include the reason for testing, test availability, and cost. Generally, it is not recommended to test a person with both a TST and an IGRA.

Diagnosis of Latent TB Infection or TB Disease

If a person is found to be infected with TB bacteria, other tests are needed to see if the person has TB disease. TB disease can be diagnosed by medical history, physical examination, chest x-ray, and other laboratory tests. TB disease is treated by taking several drugs as recommended by a health care provider.

If a person does not have TB disease, but has TB bacteria in the body, then latent TB infection is diagnosed. The decision about taking treatment for latent TB infection will be based on a person’s chances of developing TB disease.

Related Links

• CDC Tuberculosis (TB)
• Basic TB Information

Tuberculosis (TB) Blood Test (IGRA)

On this page:
What is a TB blood test?
You should have TB blood (or TB skin test) if you:
How can I get a TB blood test?
What if my TB blood is “negative”?
What if my TB blood is “positive”?
What is latent TB infection?
What if I’ve had the BCG vaccine?

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What is a TB blood test?

The tuberculosis (TB) blood test, also called an Interferon Gamma Release Assay or IGRA, is a way to find out if you have TB germs in your body. The TB blood test can be done instead of a TB skin test (Mantoux).

There are two kinds of TB blood tests:

• QuantiFERON®-TB
• T-SPOT®.TB

You should have a TB blood (or TB skin test) if you:

• have had frequent close contact with someone who has active TB disease,
• have lived in a country where many people have TB,
• work or live in a nursing home, clinic, hospital, prison, or homeless shelter, or
• have HIV infection or your immune system is not very strong.

Children less than 2 years old should have the TB skin test instead of the TB blood test.

How can I get a TB blood test?

Ask your health care provider. They will draw a small amount of blood and send it to a laboratory. Your health care provider should tell you if your test result is “negative” or “positive” in a few days.

What if my TB blood is “negative”?

A “negative” TB blood test result usually means that you don’t have TB germs in your body.

What if my TB blood is “positive”?

A “positive” TB blood test result means you probably have TB germs in your body. Most people with a positive TB blood test have latent TB infection. To be sure, your doctor will examine you and do a chest x-ray. You may need other tests to see if you have latent TB infection or active TB disease.

What is latent TB infection?

There are two phases of TB. Both phases can be treated with medicine.

When TB germs enter your body, they cause latent TB infection. Without treatment, latent TB infection can become active TB disease.

Phase 1 – Latent TB Infection	Phase 2 – Active TB Disease
TB germs are “asleep” in your body. This phase can last for a very long time – even many years.	TB germs are active and spreading. They are damaging tissue in your body.
You don’t look or feel sick. Your chest x-ray is usually normal.	You usually feel sick. Your doctor will do special tests to find where TB is harming your body.
You can’t spread TB to other people.	If the TB germs are in your lungs, you can spread TB to other people by coughing, sneezing, talking, or singing.
Usually treated by taking one medicine for 9 months.	Treated by taking 3 or 4 TB medicines for at least 6 months.

What if I’ve had the BCG vaccine?

The BCG vaccine (TB vaccine) may help protect young children from getting very sick with TB. This protection goes away as people get older. People who have had BCG vaccine still can get latent TB infection and active TB disease.

If you had the BCG vaccine and you have a choice of having a TB blood test or a TB skin test, it is better for you to have the TB blood test. This is because the TB blood test is not affected by the BCG vaccine. This means that your TB blood test will be “positive” only if you have TB germs in your body.

Protect your health and the health of your family – get a TB blood test!

T-SPOT.TB – indications, preparation, benefits of the TB test

+7 (495) 276 08 08

Diagnosis of latent and active TB infection by T-SPOT.TB

T-SPOT

Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis (Koch’s rods). The infection mainly affects the lung tissue, but can spread to other organs. Tuberculosis does not go away on its own. To cope with the disease, timely diagnosis and high-quality treatment are necessary.

Tuberculosis is rarely talked about outside the medical community. There are many myths around this disease. The main one is that tuberculosis is an extremely rare, almost extinct infection. In fact, in many countries, including Russia, there is now an epidemic of tuberculosis, and every fourth carrier of a latent infection. At any moment, the latent form can turn into an open one, and the person will become dangerous to others. At the same time, in a latent form, tuberculosis can go unnoticed for many years, it does not cause symptoms and does not affect well-being.

Most methods for diagnosing tuberculosis do not allow detecting an infection in a latent form. The most advanced and accurate analysis that detects latent and active tuberculosis at the same time is T-SPOT.

What is T-SPOT

T-SPOT is a progressive method for diagnosing tuberculosis. Unlike subcutaneous Mantoux and Diaskintest tests, the T-SPOT method excludes patient contact with tuberculin and Mycobacterium tuberculosis antigens, there is no need to provoke an immune response. All that is needed for T-SPOT analysis is a standard blood sample.

Benefits of the T-SPOT method:

How the T-SPOT method works

During the study, the number of T-lymphocytes that produce interferon-gamma is determined in a blood sample. Due to this, it is revealed if there is an immune response and if Mycobacterium tuberculosis is present in the body.
The principle of the test is also reflected in its name: the letter “T” means T-lymphocytes, based on the reaction of which the analysis itself is carried out. “SPOT” is translated as “spot” – it is formed during the reaction if an infection is detected.
Testing takes place “in vitro” – in vitro. Thanks to this, the test is completely safe, has no contraindications and cannot cause adverse reactions.

Who needs T-SPOT

How to prepare for analysis

Special preparation for the study is not required.

Blood sampling is carried out on an empty stomach or not earlier than 4 hours after a light meal. It is permissible to drink pure non-mineral and non-carbonated water. Tea, coffee, juice are prohibited. The day before, avoid overeating, physical activity and emotional overstrain.

IMPORTANT:

The Mantoux test does not affect the result of the ELISPOT test for the diagnosis of tuberculosis infection, so it can be performed independently of the test.

After the Diaskin test, this study can be carried out no earlier than 2 months later.

During acute respiratory infections, a non-specific reaction may occur that interferes with the evaluation of the result. Therefore, it is preferable to do the test no earlier than 1 month after recovery.

What to choose?

T-SPOT

Mantoux

Diaskintest

Quantiferon test

At the moment, there are 4 main methods for diagnosing tuberculosis:

1. Two skin tests (Mantoux, Diaskintest)

2. Two laboratory blood tests (T-SPOT, Quantiferon test).

Of all the methods, T-SPOT is considered the most modern and accurate.
The specificity and sensitivity of the technique is 99%.
For the Mantoux test, these figures vary in the region of 70–80%.

Comparison of methods for diagnosing tuberculosis

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Tuberculosis and COVID-19

About 25% of the world’s inhabitants are infected with tuberculosis infection.
Most of those infected will be lucky and never know about it.
But you need to remember that the infection can wake up at any time – usually this happens against the background of reduced immunity.

The state of immunity is affected by chronic diseases, autoimmune and oncological processes, heavy therapy, and taking a number of medications. A separate group of people who are at risk for tuberculosis are HIV-infected. Russia has been experiencing an HIV epidemic for many years.

But HIV is not the only virus that destroys the immune system and makes the body defenseless against Mycobacterium tuberculosis. Since the beginning of 2020, the world has been living in a new coronavirus epidemic caused by the Sars-Cov-2 strain.

COVID-19 affects the lungs, and its complications have devastating effects on the cardiovascular system, liver, and other organs. Coronavirus weakens the body and reduces the defenses of the immune system. During the course of a coronavirus infection and a long recovery period after it, a person becomes especially vulnerable to tuberculosis. If the patient was a carrier of a latent form of tuberculosis, the risk increases that it will go into the active stage.

Despite all the efforts of the medical community and the development of medicine, tuberculosis is still among the ten leading causes of death in the world. Among infectious diseases, it ranks first, even ahead of HIV and coronavirus. Tuberculosis kills about 1.5 million people every year. About 10 million more are infected with tuberculosis each year.

Against the background of the coronavirus epidemic, WHO expects an increase in mortality from tuberculosis. People with tuberculosis, even in latent form, are more susceptible to contracting the coronavirus. Conversely, those who recovered from COVID-19are at risk for tuberculosis. A particularly difficult task for doctors is the simultaneous infection with coronavirus and tuberculosis, which is also not excluded.

Due to the similarity of the symptoms of coronavirus and tuberculosis, parallel diagnostics of these two diseases can be recommended, which will make it possible to make an accurate and complete diagnosis and prevent the spread of infections. Testing for tuberculosis after a coronavirus infection is also recommended.

The service can be used at the CITILAB medical center or at home.

Tuberculosis testing: which method to choose?

Mantoux reaction, Diaskin test, quantiferon test, T-spot, PCR, or maybe fluorography? Let’s tell you more.

Tuberculosis in Russia is so widespread that by the age of forty 70-90% of the inhabitants of our country are infected with it. This does not mean that they are sick: after infection, the immune system of most people copes with the bacterium. The probability of getting sick is on average 8% in the first two years after infection, then it gradually decreases, and acquired cellular immunity is formed. Among adults, people who are weakened, living in poor conditions, with a lack of light and fresh air, are more likely to get sick. However, absolutely anyone of us can get infected. That’s why it’s so important to get regular TB checks and check your kids.

IMPORTANT! Information from the article cannot be used for self-diagnosis and self-treatment! Only a doctor can prescribe the necessary examinations, establish a diagnosis and draw up a treatment plan for a consultation!

Why is the BCG vaccine needed?

WHO recommends mass vaccination of newborns against tuberculosis in all countries where the disease is prevalent. Therefore, on the 3-5th day after birth, even in the maternity hospital, all newborns are vaccinated with BCG free of charge. But this vaccine does not protect against TB infection. Her task is somewhat different. If an unvaccinated child younger than 2 years of age is infected with TB, they are very likely to develop TB meningitis and generalized forms of TB, which can lead to death very quickly. BCG quite reliably protects the child from these forms. It also protects children from pulmonary TB, but less effectively.

What other vaccinations do children under 2 years of age need?

Mantoux test

Mantoux test is performed annually for all children up to 7 years of age. This is not a vaccination (!), but an immunological test that shows whether there is a causative agent of tuberculosis in the body. In this case, tuberculin is injected intradermally – a specific protein containing antigens of human and bovine tuberculosis. After 72 hours, the size of the papule is measured. The result of the Mantoux reaction can be affected by visiting the sauna, taking a long bath, swimming in the pool and scratching the injection site. Temporary contact with water does not affect the results of the Mantoux test in any way, so the opinion that Mantoux cannot be wetted is a myth.

Diaskintest test

It is carried out for children from 8 years old. It is also a skin test. But if antigens of both human and bovine tuberculosis are used in Mantoux, then only antigens of human tuberculosis are used in diaskintest. Diaskintest is much more specific: a reaction to it occurs only if there are active tuberculosis bacteria in the body. Simply put, if the Mantoux test is positive, it still does not mean anything: this test often gives false positive reactions. But after the diaskintest, a reaction appeared – this is a more serious indicator.

The accuracy of Mantoux is 50-70%, Diaskintest is 90%.

Quantiferon test

Quantiferon test is one of the new methods for diagnosing tuberculosis by blood test. It is based on the determination of gamma-interferon in the blood, which cells produce in response to the introduction of a tubercle bacillus. Unlike Mantoux and Diaskintest, the quantiferon test does not require the introduction of any antigens and bacteria into the body. Blood for research is taken from a vein. The result is ready in a few days, and its accuracy is much higher than that of skin tests. The test will only be positive if the person is really sick.

T.SPOT.TB (“tee-spot”)

This method of diagnosing tuberculosis by blood is similar to the quantiferon test. The difference is that the quantiferon test detects gamma-interferon in the blood, which is produced in response to the introduction of a tubercle bacillus, and T-POTS determines the T-cells themselves, which produce gamma-interferon in the presence of Mycobacterium tuberculosis. Both tests are equally sensitive and informative (up to 97%), they are more sensitive than diaskintest and much more sensitive than the Mantoux reaction. “Te-spot” virtually eliminates false positive and false negative reactions, while the quantiferon test can still give a false positive reaction if, for example, a person was sick with ARVI at the time of blood donation.

Comparative characteristics of four tuberculosis tests

9 0088 No

	Mantoux	Diaskintest	Kwan tiferon test	T. SPOT.TB
Precision	50, 00%	90.00%	97.00%	97.00%
Evaluation of data	Subjective	Subjective	Objective	Objective
False positives	Common	Rare	Extremely rare
With latent form of tuberculosis	Not reliable	Not reliable	Reliable	Reliable
Contraindications	Many	Yes	No	No
With HIV and other immunodeficiencies	Not informative	Not informative	Informative	Informative
Test method	Skin test	Skin test	Blood test	Blood test

PCR

To distinguish between active and latent tuberculosis, a specific test is used – PCR (sputum DNA testing).