Question:
Whole blood is used as a sample for which test?
Whole blood is used as a sample for which test?
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Which TB test needs live T cells to pump out interferon-gamma against TB antigens?
Updated On: Jun 23, 2026
- Bacteria
- IGRA
- GeneXpert
- Virus
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The Correct Option is B
Solution and Explanation
Step 1: Interferon-Gamma Release Assays (IGRAs) such as QuantiFERON-TB Gold and T-SPOT.TB are designed to detect latent or active Mycobacterium tuberculosis infection.
Step 2: The principle requires viable T lymphocytes: fresh whole blood is incubated with TB-specific antigens (ESAT-6, CFP-10), and sensitised T cells release interferon-gamma, which is measured. Live cells are essential, so whole blood is the required sample. Option (b) is correct.
Step 3: Because it uses M. tuberculosis-specific antigens, IGRA is not confounded by prior BCG vaccination, an advantage over the tuberculin skin test.
Step 4: The other options are not specific whole-blood-dependent tests: bacterial and viral cultures/diagnostics use varied specimens (serum, swabs, tissue, plasma), and GeneXpert for TB is run on sputum, not whole blood.
Step 2: The principle requires viable T lymphocytes: fresh whole blood is incubated with TB-specific antigens (ESAT-6, CFP-10), and sensitised T cells release interferon-gamma, which is measured. Live cells are essential, so whole blood is the required sample. Option (b) is correct.
Step 3: Because it uses M. tuberculosis-specific antigens, IGRA is not confounded by prior BCG vaccination, an advantage over the tuberculin skin test.
Step 4: The other options are not specific whole-blood-dependent tests: bacterial and viral cultures/diagnostics use varied specimens (serum, swabs, tissue, plasma), and GeneXpert for TB is run on sputum, not whole blood.
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