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Section 5 of 6 · Open sections

Required section · Section 5 of 6

Classify evidence and choose the bounded action

A normal average MCV does not exclude a mixed red-cell population. Mixed iron and B12 or folate deficiencies can normalize MCV while increasing RDW. The histogram below illustrates a reference-range average MCV with separate small and large cell populations.

For the guided case, rank the macro-ovalocytic smear pattern, low reticulocytes, and functional-marker pattern above unsupported disease-name guessing. Pancytopenia requires qualified morphology review and escalation through the local morphology-review and critical-result escalation procedure. Dysplasia or blasts also require that escalation pathway.

Illustrative drawing — this picture was drawn rather than captured.

Histogram shows microcytic and macrocytic cell populations around an average MCV of 94 fL with increased RDW 19.2 percent.
Figure 1Red-cell volume histogram showing a mixed population.
Mixed red-cell populations shown in the histogram
PopulationApproximate MCVNote
Microcytic peak75 fLSmaller red-cell subpopulation
Macrocytic peak120 fLLarger red-cell subpopulation
Average MCV94 fLWithin the 80-100 fL reference band
RDW19.2%Increased despite a reference-range average MCV

Ordering exercise

Place the review actions in the sequence that protects the interpretation from a misleading MCV.

  1. 1. Correlate targeted markers

    Interpret nutrient markers and chemistry with assay and renal context.

  2. 2. Review qualified morphology

    Classify morphology and identify escalation findings.

  3. 3. Assess reticulocyte response

    Determine whether regeneration may increase MCV.

  4. 4. Confirm CBC and specimen

    Review specimen condition, analyzer flags, count, and hematocrit.

Knowledge checks

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Knowledge check 1

Which findings require qualified morphology review and escalation through the local morphology-review and critical-result escalation procedure?

Choose at least 3 options.

Knowledge check 2

A reference-range MCV with increased RDW can mean what in the appropriate CBC context?

Choose one option.

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