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Section 2 of 6 · Open sections

Required section · Section 2 of 6

What a distribution plot measures

A measurement channel is a defined analytical path. In this XN-series workflow, the impedance RBC/platelet path sizes particles by electrical impedance. WDF (white-cell differential) uses forward-scattered light (FSC), side-scattered light (SSC), and side-fluorescent light (SFL) after channel-specific preparation; its displayed scattergram plots SSC against SFL. WNR (white-cell/nucleated-red-cell) is a separate fluorescence-flow channel used to distinguish WBCs from NRBCs. FSC, SSC, and SFL are signal names, not diagnoses. VCS (volume, conductivity, scatter) is a different, Beckman Coulter method family and is not a signal set or channel in this XN workflow.

For an impedance histogram, the mode is the volume with the greatest event density. RDW-CV is the coefficient of variation of the RBC volume distribution, expressed as a percentage; it depends on distribution width relative to MCV. RDW-SD is the direct histogram width in fL at the analyzer-defined height. Curve fitting is a mathematical approximation of a distribution, not a replacement for the observed event pattern or smear. These index definitions describe distributions; they do not assign a cause.

A scattergram maps simultaneous channel measurements into event clusters. Cluster position, dispersion, overlap, or events outside expected regions can trigger a review decision. Plot quality must also be assessed: sparse events, truncated axes, debris/background, or an obstructed flow cell can mimic or obscure a population, so follow the local repeat/quality procedure before interpretation. Name the channel and measured pattern first, then obtain the evidence required by the local rule.

Illustrative drawing — this picture was drawn rather than captured.

Four impedance histograms compare normal and review patterns. RBC panels plot event density against volume in fL: the normal curve marks its mode; the review curve is broad with a shoulder and two separated peaks labeled as a dual population. Platelet panels use the same axes and show a high-volume tail toward the platelet/RBC boundary. The legend identifies normal and review curves. Sparse events, debris, or truncation require quality or repeat review.
Figure 1Impedance-volume normal and review comparisons show event density, mode, broadening/shoulder, a true dual population, and a platelet high-volume tail; correlate with indices, specimen, and smear.
Normal-versus-review impedance distribution pattern reference
Pattern featureNormal comparisonReview pattern
Mode (RBC volume)Single peak at the usual event-density maximumMay be shifted from the normal-comparison mode
Broadening / shoulderNarrow, symmetric curveWidened curve with an asymmetric shoulder
Dual populationNot presentTwo separable event-density peaks
Platelet high-volume tailCurve returns to baseline before the platelet/RBC boundaryTail extends toward the platelet/RBC boundary

Method-declared evidence sequence: use a validated local rule to make a release, review, repeat, or escalation decision.

  1. Declare method

    Identify analyzer, channel or plot, and software version before interpretation.

  2. Read signal pattern

    For the named channel, identify a distribution width, shoulder, tail, cluster dispersion, overlap, or unclassified events.

  3. Correlate result

    Compare CBC relationships, analyzer status, and tube appearance; do not treat a visual plot pattern as a diagnosis.

  4. Choose bounded action

    Choose the locally validated outcome: release, smear review, repeat/alternate measurement, recollection, or escalation.

Knowledge checks

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Knowledge check 1

A modeled XN-series report has an atypical WDF scattergram and an NRBC-related review flag. Which method declarations must be made before choosing an action? Select all that apply.

Choose at least 2 options.

Knowledge check 2

A broad RBC histogram is paired with a raised RDW. Which next decision is supported before a cause is reported?

Choose one option.

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