SCYM Principles of Flow Cytometry & Instrumentation 5

Question 1

What is the significance of the 'coefficient of variation' (CV) when evaluating flow cytometer performance?

Accepted Answer

It quantifies the spread (precision) of a fluorescent bead or cell population around its mean

Answer

CV (standard deviation ÷ mean × 100%) measures how tightly a population clusters around its mean intensity; lower CV indicates better instrument precision and resolution.

Question 2

Which of the following best describes 'carryover' (also called cross-contamination) in a flow cytometer?

Accepted Answer

Residual cells from a previous sample that appear in the next sample's data

Answer

Carryover occurs when cells from a highly concentrated or strongly positive previous sample remain in the fluidic system and contaminate subsequent sample acquisitions.

Question 3

What is the role of the 'sample core' in hydrodynamic focusing?

Accepted Answer

It is the central narrow stream of sample fluid containing the cells being analyzed

Answer

The sample core is the inner fluid stream containing cells; it is focused to a narrow diameter by surrounding sheath fluid, ensuring cells pass through the laser one at a time.

Question 4

Why is it important to use antibody capture beads (rather than cells) as compensation controls when possible?

Accepted Answer

Beads have no autofluorescence, giving a cleaner negative population than cells

Answer

Antibody capture beads have minimal autofluorescence, providing a very clean negative population and a bright positive signal, which makes setting compensation values more accurate than using cells.

Question 5

In a cell sorter, what is the 'sort delay' (or 'drop delay') calibration used for?

Accepted Answer

Determining the precise time between laser interrogation and droplet charging to ensure the correct droplet is deflected

Answer

Sort delay calibration determines the exact time between when a cell is analyzed at the laser and when the droplet containing that cell breaks off and must be charged for deflection into the sort gate.

(SCYM) Specialist in Cytometry Practice Test

(SCYM) Specialist in Cytometry Practice Test

SCYM Principles of Flow Cytometry & Instrumentation 5