The Quantiferon-TB IGRA Test is used to check for TB infection. Tuberculosis is an infectious disease that affects the lungs and other body parts. It can be further categorized as being either latent or active. Active TB causes symptoms and is contagious. Latent TB isn’t contagious and doesn’t cause symptoms. The Quantiferon-TB IGRA Test detects immune responses to tuberculosis infection. The CDC recommends it as an alternative to the tuberculin skin test in certain situations. This blood test can also be used to assist with diagnosis when a person is showing symptoms of TB disease. The Quantiferon-TB IGRA Test measures the amount of interferon-gamma (IFN-g), which is a specific protein produced by a person’s T cells. You may be ordered to get this test if your working conditions or living situation puts you at risk for exposure to TB.  

What is a Quantiferon-TB IGRA Test? 

The Quantiferon-TB IGRA Test is used to check for TB infection. Tuberculosis is an infectious disease that affects the lungs and other body parts. It can be further categorized as being either latent or active. Active TB causes symptoms and is contagious. Latent TB isn’t contagious and doesn’t cause symptoms. The Quantiferon-TB IGRA Test detects immune responses to tuberculosis infection. The CDC recommends it as an alternative to the tuberculin skin test in certain situations. This blood test can also be used to assist with diagnosis when a person is showing symptoms of TB disease. The Quantiferon-TB IGRA Test measures the amount of interferon-gamma (IFN-g), which is a specific protein produced by a person’s T cells. You may be ordered to get this test if your working conditions or living situation puts you at risk for exposure to TB.  

If a Quantiferon-TB IGRA Test shows a positive result, clinical assessments and follow-up tests are used to check whether tuberculosis infection has progressed in the patient to active TB disease. Children under 2 years are advised to get the TB skin test instead of the Quantiferon-TB IGRA test. 

What is the purpose of the Quantiferon-TB IGRA Test? 

The Quantiferon-TB IGRA Test can aid in the diagnosis of Mycobacterium tuberculosis infection. It measures a person’s immune system’s reactivity to Mycobacterium tuberculosis. The WBC of most persons infected with M. tuberculosis releases interferon-gamma when mixed with antigens derived from M. tuberculosis. This is the preferred method of TB infection testing for people who have received the BCG vaccination.  

What does the Quantiferon-TB IGRA Test Diagnose? 

The Quantiferon-TB IGRA Test is used to detect Mycobacterium tuberculosis infection. It is an alternative to the tuberculin skin test for latent tuberculosis. QuantiFERON-TB is also known as an interferon-gamma release assay because Mycobacterium tuberculosis peptide antigens lead to interferon-gamma release from the T cells of patients having the infection. This test can be used to diagnose latent and active TB and is more specific than tuberculin skin testing in people who have got BCG vaccination. If you had the BCG vaccine, you should get the TB blood test because it is not affected by the BCG vaccine.  

Why Do You Need a Quantiferon-TB IGRA Test? 

Certain people need to be tested for TB bacteria as they are more likely to get the infection, including: 

• People with TB disease symptoms like night sweats, high fever, cough, cold, and sudden weight loss. 

• People who live or have returned from a country with prevalent TB disease. TB infection is quite common in most countries in the Caribbean, Latin America, Africa, Asia, Russia, and Eastern Europe.  

• People who have been in close contact with someone having a TB infection. 

• People with HIV or other medical problems that weaken the immune system. 

• People who work or live in homeless shelters, nursing homes, prisons, or jails where TB is quite common.  

This test is also recommended for patients on immunosuppressive therapy and biological treatment. 

Preparation and procedure required for the Quantiferon-TB IGRA Test 

You don’t need to do any special preparations before the Quantiferon-TB IGRA Test. If you’re taking any medications or drugs, you must inform your doctor beforehand, as they may lead to inaccurate test results. You should also follow the instructions of the doctor or technician to ensure that the test results are accurate. 

During the Quantiferon-TB IGRA Test, the technician will draw a small amount of blood from the vein in your arm. The technician will clean the blood draw site with an antiseptic to avoid any chances of infection. A band made of elastic material will be placed around your upper arm to restrict blood flow and ensure that the veins are clearly visible. The technician will insert a small needle into your vein and collect the blood sample in a vial. After the blood collection process, the technician will place an adhesive bandage over the puncture site and remove the elastic band. The blood sample will be sent to the lab for detailed analysis. 

Understanding the Quantiferon-TB IGRA Test results 

IGRA interpretations are based on the amount of IFN-g or the number of cells that release IFN-g. A positive result indicates there was an immune reaction to the tuberculosis bacteria, and you have the infection. A negative result indicates there was no immune reaction to the tuberculosis bacteria, and you don’t have a TB infection. An uninterpretable result indicates the test result was borderline, invalid, or indeterminate. 

People with a positive Quantiferon-TB IGRA test mostly have latent TB infection. Your healthcare provider will examine you and can even order a chest x-ray to confirm the infection. You may be ordered other tests to see if you have active TB disease or latent TB infection.