SCYM Clinical Applications 2 — Questions and Answers
Question 1: Which flow cytometric assay is the gold standard for diagnosing paroxysmal nocturnal hemoglobinuria (PNH)?
- CD55/CD59 expression on red blood cells and granulocytes (Correct answer)
- CD34 quantification on peripheral blood
- Annexin V binding assay
- CD41/CD61 platelet glycoprotein panel
Correct answer: CD55/CD59 expression on red blood cells and granulocytes
PNH is diagnosed by demonstrating GPI-anchor deficiency via loss of CD55 and CD59 on erythrocytes and granulocytes using flow cytometry.
Question 2: In a bone marrow transplant setting, chimerism analysis by flow cytometry is best performed using which approach?
- HLA-specific antibodies targeting donor vs. recipient alleles (Correct answer)
- CD45 fluorescence intensity gating only
- Measurement of mitochondrial DNA copy number
- Ki-67 proliferation index comparison
Correct answer: HLA-specific antibodies targeting donor vs. recipient alleles
HLA allele-specific antibodies allow discrimination of donor versus recipient cells for post-transplant chimerism monitoring.
Question 3: A patient with suspected B-cell lymphoma shows CD10+, BCL-6+, CD5-, CD23- immunophenotype. Which diagnosis is most consistent?
- Follicular lymphoma (Correct answer)
- Mantle cell lymphoma
- Chronic lymphocytic leukemia
- Marginal zone lymphoma
Correct answer: Follicular lymphoma
Follicular lymphoma classically expresses CD10 and BCL-6 while lacking CD5 and CD23.
Question 4: Which surface marker combination is most specific for identifying plasma cells by flow cytometry in bone marrow?
- CD138+/CD38bright/CD19-/CD45dim (Correct answer)
- CD20+/CD79a+/CD10+/CD38dim
- CD3+/CD56+/CD16+/CD138-
- CD34+/CD117+/CD33+/CD138-
Correct answer: CD138+/CD38bright/CD19-/CD45dim
Plasma cells are CD138+, CD38bright, CD19-/dim, and CD45dim/negative, distinguishing them from other B-lineage cells.
Question 5: In HIV monitoring, the CD4:CD8 ratio typically falls below what threshold to indicate significant immunosuppression?
- 1.0 (Correct answer)
- 2.0
- 0.5
- 3.0
Correct answer: 1.0
A CD4:CD8 ratio below 1.0 indicates immune inversion and is associated with significant immunosuppression in HIV disease.
Question 6: Which flow cytometry finding is characteristic of hairy cell leukemia?
- CD11c+/CD25+/CD103+/CD123+ B cells (Correct answer)
- CD5+/CD23+/dim surface Ig B cells
- CD10+/CD34+/TdT+ B cells
- CD20-/CD38bright/CD138+ cells
Correct answer: CD11c+/CD25+/CD103+/CD123+ B cells
Hairy cell leukemia characteristically coexpresses CD11c, CD25, CD103, and CD123 on mature B cells.
Question 7: When quantifying CD34+ stem cells for transplantation, the ISHAGE gating strategy begins with which initial gate?
- CD45 vs. side scatter to identify the leucocyte blast region (Correct answer)
- Forward scatter vs. side scatter to exclude debris
- CD34 vs. CD45 dual positivity directly
- Viability dye exclusion as the primary gate
Correct answer: CD45 vs. side scatter to identify the leucocyte blast region
The ISHAGE protocol begins with a CD45/SSC gate to define the leukocyte-containing region before applying sequential CD34 gating.
SCYM Clinical Applications 2
Which flow cytometric assay is the gold standard for diagnosing paroxysmal nocturnal hemoglobinuria (PNH)?