Which type of test does the QuantiFERON-TB gold test fall under?

The QuantiFERON-TB Gold test is classified as an immunologic test because it measures the immune response to specific TB antigens. This test works by assessing the presence of a delayed-type hypersensitivity response in individuals who may have been exposed to the tuberculosis bacterium (Mycobacterium tuberculosis).

During the test, a small amount of specific TB proteins is introduced into the patient's blood sample. If the individual's immune system has been sensitized to these proteins, typically due to a previous exposure to the bacteria or vaccination with the Bacillus Calmette-Guérin (BCG) vaccine, the immune cells will react and produce certain immune markers, which can then be measured. This reaction is indicative of an immune response to the tuberculosis infection, thereby aiding in the diagnosis.

In contrast, other types of tests mentioned, such as serological tests, assess the presence of antibodies in the serum, cultural tests involve culturing bacteria to identify and diagnose infections, and genetic tests look for specific DNA sequences associated with pathogens. The nature of the QuantiFERON-TB Gold test specifically focusing on cellular immunity and the response to antigens aligns it squarely within the category of immunologic tests.