SCYM Sample Preparation & Staining Techniques 3

Question 1

What is the recommended maximum time between blood draw and staining for optimal flow cytometric immunophenotyping?

Accepted Answer

24-48 hours

Answer

EDTA-anticoagulated whole blood can be stained within 24-48 hours of collection when stored at room temperature, though same-day processing is ideal.

Question 2

Which anticoagulant is preferred for flow cytometric analysis of platelet activation markers?

Accepted Answer

Sodium citrate

Answer

Sodium citrate is preferred for platelet studies because EDTA chelates calcium and can activate or alter platelet surface antigens, while citrate better preserves platelet function.

Question 3

When staining bone marrow aspirates, which step is critical to perform BEFORE antibody addition?

Accepted Answer

Counting viable cells and adjusting to the target cell concentration

Answer

Adjusting to a consistent cell concentration (typically 1×10⁶ cells per test) before antibody addition ensures accurate antibody-to-cell ratios and prevents under- or over-saturation.

Question 4

Which viability dye is excluded by live cells and enters only cells with compromised membranes?

Accepted Answer

7-Aminoactinomycin D (7-AAD)

Answer

7-AAD is a membrane-impermeant DNA intercalating dye that only enters cells with damaged membranes, making it an effective dead cell exclusion dye.

Question 5

What is the purpose of adding DNase to dissociated tissue samples prior to flow cytometry?

Accepted Answer

To reduce cell clumping caused by free DNA from dead cells

Answer

Free DNA released from dead cells is sticky and causes cell clumping; DNase digests this free DNA to produce a single-cell suspension.

(SCYM) Specialist in Cytometry Practice Test

(SCYM) Specialist in Cytometry Practice Test

SCYM Sample Preparation & Staining Techniques 3