Required section · Section 3 of 6

Focused instruction: separate preparation effects from cell findings

Review the monolayer just behind the feathered edge for red-cell central pallor and distribution. Hypochromia is reduced hemoglobinization seen as central pallor clearly exceeding about one-third of RBC diameter. Mean corpuscular hemoglobin (MCH) is the calculated average hemoglobin mass per RBC, and mean corpuscular hemoglobin concentration (MCHC) is the calculated average hemoglobin concentration in packed RBC volume; use these indices rather than visual grading alone when available.

Normal platelets are spread as singles and small loose groups across the monolayer. Clumps at an edge or platelets rosetting around neutrophils, called satellitism, can make an automated count falsely low in an EDTA specimen. Giant platelets may also be misrepresented by impedance counting. A smear platelet estimate corroborates plausibility; it is not a replacement count.

Mean platelet volume (MPV) is an analyzer-estimated platelet size, not a direct microscopic measurement, and is method-dependent. Impedance methods estimate platelet volume from pulse amplitude, while optical methods derive size from light-scatter signal, so results are not numerically interchangeable. EDTA storage can change platelet shape and MPV over time.

Three text-labelled panels compare a normal monolayer, a feathered-edge clump, and platelet satellitism; only the edge-clump panel includes a drawn diagonal edge band, the other panels are text only. — Figure 1Platelet distribution distinguishes a normal monolayer from an edge clump or satellitism.

Ordering exercise

Place these actions in the order that supports a platelet-result discrepancy review.

1. Follow local policy

Document and escalate or obtain a citrate redraw when the procedure requires it.
2. Inspect edges

Search feathered and lateral edges for clumps or displaced material.
3. Compare analyzer result

Decide whether visible findings plausibly explain the automated result.
4. Inspect monolayer

Assess platelet distribution and RBC background where cells barely touch.

Knowledge checks

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Knowledge check 1

An unexpectedly low automated platelet count has visible clumps and satellitism on smear review. Which actions are supported?

Choose at least 2 options.

Use the smear findings to assess whether the analyzer result may be misleading

Follow the established local escalation or citrate-redraw procedure

Release the low count as true without reviewing the film

Replace the analyzer result with a universal platelet-per-field conversion

Knowledge check 2

Why should an MPV value not be compared directly across all analyzers or delayed EDTA specimens?

Choose one option.

MPV depends on analyzer method, anticoagulant, and collection-to-analysis interval

MPV has one universal reference interval

MPV is measured from the smear

Section status

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