<prompt> Which of the following statements regardingGamma-Release-Assays for diagnosis of Tuberculosis is true -First Generation Quanti FERON-TB assay used ESAT-6Second Generation Quanti FERON-TB Gold assay used ESAT-6 and CPF-10These tests can distinguish between M. tuberculosis and M. bovisNone of the non-tuberculosis mycobacteria give a positive reaction with the test  <response>: Ans. is b i.e., Second Generation Quantiferon-TB Gold assay used ESAT-6 and CPF-10 These are also called Interferon-Gamma release assays because these detect release of IFN-y from persons who have been exposed to Mycobacterium-tuberculosis complex. It is an ELISA based test. Blood of the patient is exposed with a specific M. tuberculosis antigen and the production of IFN-y is measured by ELISA. Based on antigen used, these assays are divided into three types :- i First generation or QuantiFERON TB QFT :- It responds to 1 tubercular protein, PPD purified protein derivative. ii Second generation or QuantiFERON TB Gold QFT-G :- This responds to 2 tubercular proteins : 1 ESAT-6 earyl secretory antigen target-6, and 2 CFP-10 culture filtrate protein-10. ESAT-6 and CFP-10 are secreted by all M. tuberculosis and pathogenic M. bovis strains. Therefore, test cannot distinguish between M. tuberculosis and M. bovis strains. Most non-tubercular mycobacteria do not secrete ESAT-6 and CFP-10. However, some nontubercular mycobacteria such as M. Kansasii, M. szulgai and M. maximum may secrete ESAT-6 and CFP-10 and hence test positive. iii Third generation or QuantiFERON TB Gold In-Tube QFT-GIT :- This responds to 3 tubercular proteins : 1 ESAT-6, 2 CFP-10, and 3 TB 7.7. 