Quantiferon-TB Gold Gamma Interferon Test

 What is a Quantiferon TB gold Test?

A potentially severe infectious disease that primarily affects the lungs is tuberculosis (TB). Mycobacterium tuberculosis is the bacteria that causes TB. Immunosuppression can cause the activation of dormant TB bacilli. Detection of this dormant TB can be a practical step in preventing TB infection. A blood test called QuantiFERON-TB Gold is used to find Mycobacterium tuberculosis. An interferon-gamma (IFN-gamma) release assay is the Quantiferon TB gold test (QFT). It is typically referred to as an IGRA. It is a recent substitute for the tuberculin skin test (TST or Mantoux). Quantiferon TB gold test is done in the laboratory. This test is unaffected by previous Bacille Calmette-Guerin (BCG) vaccination.

When does the doctor prescribe the Quantiferon TB gold test?

A doctor may prescribe this test when he suspects

• TB in a patient 
• In patients who already had an infection with TB
• In patients who are habitual of using drug syringes.
• Diseases that weaken the immune system.

What are the components of the quantiferon TB gold test?

A whole-blood test, the TB gold test, assesses a patient's cellular immune response to tuberculosis (TB). White blood cells are used in the test, which involves incubating whole blood with antigens. Three recombinant MTB peptides are used in the Quantiferon TB Gold Gamma Interferon Test to increase interferon-gamma production by T cells in people with MTB infection.

What is the normal range of the quantiferon TB gold test?

• Negative:<0.20 IU/ml
• Borderline negative:0.20 to 0.34 IU/ml
• Borderline positive:0.35 to 0.99 IU/ml
• Positive : ≥1.0 IU/ml [1]

Note: A positive report indicates an actual infection with M. tuberculosis. Other investigations like risk assessment, medical and other diagnostic evaluation, radiography, CT chest can be done to confirm the diagnosis 

 

What are the prerequisites for the Quantiferon TB gold test?

• The sample is collected from the vein
• No special preparations are required for the test.
• There is no risk to the patient.
• The report comes between 24 to 36 hours.

 

Reference: 

[1] The Impact of Borderline Quantiferon-TB Gold Plus Results for Latent Tuberculosis Screening under Routine Conditions in a Low-Endemicity Setting A. Wikell, J. Jonsson, R. Dyrdak, A. J. Henningsson, A. Eringfält, T. Kjerstadius, E. Hålldin, H. Baqir, V. Kholod, E. Sturegård, J. Bruchfeld, T. Schön