ISAC Quality Control and Assurance 2

Question 1

Which Levey-Jennings rule flags a run as out of control when two consecutive measurements fall more than 2 standard deviations from the mean on the same side?

Accepted Answer

2₂s rule

Answer

The 2₂s rule is violated when two consecutive control values exceed the same ±2 SD limit, indicating a systematic shift.

Question 2

In flow cytometry, the coefficient of variation (CV) of a fluorescent bead peak is used primarily to assess which instrument performance characteristic?

Accepted Answer

Resolution or precision of measurement

Answer

A narrow CV on a bead peak reflects tight instrument precision; a rising CV indicates degraded resolution.

Question 3

A laboratory notices that its CD4 count results are consistently 10% higher than the previous week's values using the same reagent lot. The most likely cause is:

Accepted Answer

A systematic instrument or calibration shift

Answer

A consistent directional bias over time is characteristic of a systematic error such as a calibration or instrument drift.

Question 4

What is the primary purpose of running a process control chart in a clinical flow cytometry lab?

Accepted Answer

To monitor assay stability and detect shifts or trends before they affect patient results

Answer

Process control charts provide ongoing visual monitoring of assay performance to catch drift or shifts early.

Question 5

Which of the following best describes the purpose of a linearity study in flow cytometry instrument qualification?

Accepted Answer

Verifying that the instrument produces proportional signal output across a range of input intensities

Answer

Linearity studies confirm that the detector response is proportional to fluorescence intensity across the dynamic range.

(ISAC) International Society for the Advancement of Cytometry Practice Test

(ISAC) International Society for the Advancement of Cytometry Practice Test

ISAC Quality Control and Assurance 2