Required section · Section 5 of 6

Repair the flawed analysis

A colleague proposes reporting CD19-positive events as 4.6% because 2,286 of 50,000 acquired events are positive. Repair the statement by naming the final gate and its parent population. The appropriate denominator for this teaching question is the viable, singlet, CD45-bright lymphocyte gate. The same count may be reported against another denominator only when that different question is explicitly stated.

Review the controls before accepting the dim CD19 boundary. The case includes an unstained control, matched single-color controls including the viability dye, and a CD19 FMO. It also includes a stable time plot and back-gating evidence. These supports do not make a diagnostic claim or establish a normal range.

Specimen age is 18 hours from draw to stain. Delay can reduce viability and recovery, but an acceptable delay is specimen- and method-specific under the validated procedure. Low event counts also widen uncertainty, especially for a rare-event claim, so a minimum event target is tied to the intended result and validated method.

Case control and quality review before final gate interpretation
Review item	Case finding	Interpretive limit
Unstained control	Modest background	Shows background and autofluorescence, not the CD19 boundary
Single-color controls	Matched controls including viability dye	Used for conventional compensation
CD19 FMO	Included	Supports the dim CD19 boundary
Time plot	Stable	Supports acquisition review but not diagnosis
Back-gating	Plausible viable-singlet lymphocyte path	Checks gate path, not clinical significance

Ordering exercise

Arrange the teaching hierarchy from broad event acquisition to the final population of interest.

1. Select CD19-positive events

Apply the supported final marker gate.
2. Select viable singlets

Exclude nonviable events before marker interpretation.
3. Acquired events

All events recorded during acquisition.
4. Select CD45-bright lymphocytes

Name the lineage-parent population for the final percentage.
5. Exclude debris

Remove events not suitable for the intended cell analysis.
6. Select singlets

Reduce coincident-event contribution using a validated pulse plot.

Knowledge checks

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Knowledge check 1

Which limits should be recognized before a rare or consequential gated result is interpreted?

Choose at least 2 options.

Low event counts widen uncertainty and the minimum target is assay-specific.

Specimen delay, viability, and recoverable cell number depend on the locally validated procedure.

An 18-hour draw-to-stain interval is universally acceptable.

A fixed viability percentage is sufficient on every panel.

Section status

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