This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
Tests for Mycobacterium tuberculosis on whole blood is : 
Select and explain. 
A. Tuberculin, B. IGRA, C. GeneXpe MTB/RIF test, D. BACTEC
B: IGRA
Answer: B: IGRA 
Explanation: Interferon-Gamma Release Assays(IGRAs) are whole-blood tests that can aid in diagnosing Mycobacterium tuberculosis infection. The IGRA tests identify the presence of Mycobacterium tuberculosis infection by measuring the immune response to the TB bacteria in whole blood. They do not however help to differentiate Latent tuberculosis infection (LTBI) from tuberculosis disease. Two IGRAs that have been approved by the US Food and Drug Administration (FDA) are commercially available in the US. QuantiFERON(r)-TB Gold In-Tube test (QFT-GIT) T-SPOT(r).TB test (T-Spot) Ref: Ananthanarayana and Paniker 9th edition