What is quantiferon test?

The Quantiferon test, also known as Quantiferon-TB Gold (QFT-GB) or simply QFT, is a blood test used for the diagnosis of tuberculosis (TB) infection. It is a type of interferon gamma release assay (IGRA), which measures the immune response to TB infection.

Here are some key details about the Quantiferon test:

1. Purpose: The Quantiferon test is designed to detect the presence of the bacteria Mycobacterium tuberculosis, which causes tuberculosis. It can help differentiate between latent TB infection (LTBI) and active TB disease.

2. How it works: The test involves taking a blood sample from the individual and then exposing the blood cells to specific TB antigens. If the individual has been infected with TB, their immune system will release interferon-gamma in response to the antigens. The levels of interferon-gamma are then measured, indicating the presence of TB infection.

3. Advantages over tuberculin skin test (TST): The Quantiferon test has several advantages over the traditional TST, also known as the Mantoux test. It requires only one visit, as results can be obtained within 24 hours, while TST requires two visits. It also has a higher specificity, reducing the chances of false positive results due to cross-reactions with other non-TB mycobacteria or prior BCG vaccine.

4. Interpretation of results: The results of the Quantiferon test are reported as either positive, negative, or indeterminate. A positive result suggests the presence of TB infection, either latent or active. A negative result indicates the absence of TB infection, while an indeterminate result means the test couldn't produce a clear outcome and may need to be repeated.

5. Use in high-risk populations: The Quantiferon test is particularly valuable in high-risk populations, such as healthcare workers, individuals with weakened immune systems (e.g., HIV-positive), and close contacts of confirmed TB patients. It helps identify those who are at risk of developing active TB disease and enables timely intervention.

6. Limitations: Despite its advantages, the Quantiferon test also has some limitations. It cannot differentiate between latent infection and active disease. Additional tests, such as chest X-rays or clinical evaluation, are necessary to confirm the presence of active TB. False-negative and false-positive results can still occur, albeit less frequently than with the TST.

It is important to note that the availability and usage of the Quantiferon test may vary by country and healthcare facility. Consulting with a medical professional is advised for specific information and guidance on testing procedures and accuracy.