Quantiferon®-TB Gold Plus (Interferon Gamma Release Assay)

Tuberculosis is an infection that most often affects the lungs and is caused by a bacterium called Mycobacterium tuberculosis. An active TB infection occurs when the affected individual is experiencing TB symptoms. However, latent infection is when the TB organism is present in the individual’s body, but there are no symptoms. People with latent TB infection are not infectious and cannot spread the infection to others. However, if left untreated, this individual may develop an active infection in the future and may be able to transmit the disease.

The Quantiferon®-TB Gold Plus (Interferon Gamma Release Assay) test, also called QuantiFERON-TB Gold Plus (QFT Plus), is a modern alternative to the tuberculin skin test (TST). It assesses the specific immune response to TB, providing a more specific and sensitive analysis than the TST. A Quantiferon®-TB Gold Plus (Interferon Gamma Release Assay) test may be helpful for individuals who have been in close contact with someone with active TB, those with a history of travel to or residence in TB-endemic regions, and individuals with a weakened immune system. It is also used for healthcare workers, as well as in TB screening programs. QFT Plus is an indirect test for M. tuberculosis infection, but it is more specific than TST and is unaffected by previous BCG vaccination. It provides doctors with an accurate, reliable, and efficient assay for aiding the diagnosis of TB infection.

QFT-Plus is the newest and fourth version of the Quantiferon®-TB Gold Plus (Interferon Gamma Release Assay) test. It has new special antigen properties that work better to activate two types of immune cells, called CD4 and CD8 T-cells. This helps the test give a clearer and more complete view of how the body’s immune system is responding.

A positive result is a strong indicator of TB infection. However, a Quantiferon®-TB Gold Plus (Interferon Gamma Release Assay) test cannot be used to distinguish between active and latent TB infection and, therefore, is used in conjunction with risk assessment, radiography, and other medical and diagnostic evaluations.

Usually, no special preparation is required for a Quantiferon®-TB Gold Plus (Interferon Gamma Release Assay) test. The timing of the test can affect the accuracy of the results. If a person is tested too soon after their exposure to tuberculosis bacteria, they may have a false negative result. Doctors recommend testing at least 6 to 8 weeks after exposure to TB.

Test result ranges are approximate and may differ slightly between labs depending on the methodology and laboratory guidelines. Discuss the test reports with a doctor. Doctors may consider other factors, such as the health history, symptoms, medical conditions, and other test results, to establish a diagnosis of TB disease.