Question:medium
Whole blood is used as a sample for which test?
Whole blood is used as a sample for which test?
Show Hint
Which TB test needs live T cells to pump out interferon-gamma against TB antigens?
Updated On: Jun 23, 2026
- Bacteria
- IGRA
- GeneXpert
- Virus
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: Ask which listed test needs living immune cells. The Interferon-Gamma Release Assay (IGRA) measures cytokine output from a patient's own T cells, so it cannot work on serum or a swab.
Step 2: Procedure - fresh $whole\ blood$ is mixed with TB-specific peptides (ESAT-6, CFP-10); memory T cells previously primed by $M.\ tuberculosis$ pour out interferon-gamma, which the assay quantifies.
Step 3: Since the read-out depends on intact, responsive lymphocytes, whole blood collected in special tubes is mandatory, and the result is unaffected by BCG status.
Step 4: The rest fail the whole-blood criterion - generic bacterial and viral testing uses cultures or molecular swabs, and TB GeneXpert is a sputum-based PCR, not a whole-blood assay.
\[\boxed{\text{IGRA}}\]
Step 2: Procedure - fresh $whole\ blood$ is mixed with TB-specific peptides (ESAT-6, CFP-10); memory T cells previously primed by $M.\ tuberculosis$ pour out interferon-gamma, which the assay quantifies.
Step 3: Since the read-out depends on intact, responsive lymphocytes, whole blood collected in special tubes is mandatory, and the result is unaffected by BCG status.
Step 4: The rest fail the whole-blood criterion - generic bacterial and viral testing uses cultures or molecular swabs, and TB GeneXpert is a sputum-based PCR, not a whole-blood assay.
\[\boxed{\text{IGRA}}\]
Was this answer helpful?
0
