Required section · Section 4 of 6

Guided example: count the fragments

The EDTA specimen was collected at 09:10 and prepared at 09:42. After image inclusion review confirms an even Romanowsky-stained monolayer without edge-only distortion, count qualifying fragments and total RBCs together across systematic nonoverlapping fields.

In each field, record qualifying helmet, triangular, or keratocyte fragments and every RBC in the denominator before moving to the next nonoverlapping field. Across 1,000 RBCs, 14 qualifying fragments are counted: 14 ÷ 1,000 × 100 = 1.4%. Excluded bite, crenated, microspherocytic, and nonspecific distorted cells remain in the total-RBC denominator but are not numerator fragments.

Report: ‘Schistocytes 14/1,000 RBCs (1.4%) by microscopic count.’ In adults and full-term neonates, >1% morphologically identified schistocytes is suspicious for thrombotic microangiopathy when schistocytes predominate. In preterm infants, the ICSH reference upper limit is 5% schistocytes rather than the adult and full-term threshold; the adult threshold must not be transferred to a preterm result. Predominance increases specificity; it does not make a qualifying count invalid. The report is distinct from the clinical interpretation and local escalation decision.

Text-labeled field record shows qualify and exclude criteria for helmet, triangular, and keratocyte fragments versus bite, crenated, microspherocyte, and nonspecific poikilocyte forms. Labels show 14 qualifying fragments among 1,000 total RBCs, calculated as 1.4%; no trend line is shown. — Figure 1Text-labeled field record, nonproportional, with a 14/1,000 RBC count calculation.

Guided case results. Adult intervals are local placeholders.
Result	Value	Adult local interval	Method or comment
Hemoglobin	8.6 g/dL	12.0-16.0 g/dL	Automated CBC
Platelet count	41 × 10^9/L	150-400 × 10^9/L	Automated CBC; smear estimate consistent
Reticulocyte count	6.1%	0.5-2.5%	Optical or fluorescent method
LDH	1,120 U/L	140-280 U/L	Chemistry result for correlation
Schistocytes	14/1,000 RBCs = 1.4%	>1% suspicious when predominant	Manual microscopic count using ICSH criteria

Ordering exercise

Place the count workflow in the order that produces a standardized percentage.

1. Calculate and contextualize

Divide qualifying fragments by RBCs assessed, multiply by 100, then apply population and predominance context.
2. Identify positive forms

Count helmet, triangular, and keratocyte forms meeting criteria.
3. Select the optimal monolayer

Use a well-spread area suitable for morphology review.
4. Assess at least 1,000 RBCs

Use the denominator required for a reported percentage.

Knowledge checks

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Knowledge check 1

Across systematic nonoverlapping fields, 14 qualifying fragments are counted among 1,000 total RBCs. What percentage is reported?

Choose one option.

1.4%

14%

0.14%

Knowledge check 2

Which statements correctly limit interpretation of the 1.4% result? Select all that apply.

Choose at least 2 options.

The adult or full-term threshold applies when schistocytes are predominant.

The adult threshold must not be transferred to preterm infants.

The result specifically diagnoses TTP.

An automated parameter can replace the microscopic count.

Section status

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