A healthy 47-year-old man has a routine CBC on an analyzer that sorts white cells by light scatter after a cytochemical peroxidase stain and also has a separate lobularity channel. Results: WBC 6.9 × 10^3/µL (6.9 × 10^9/L); peroxidase channel: neutrophils 5%, lymphocytes 31%, monocytes 4%, eosinophils 2%, large peroxidase-negative cells 58%. The lobularity channel counts 64% polymorphonuclear cells. Hemoglobin and platelets are normal, the sample is 2 hours old, and the controls and other patients on the run are normal. The blood film shows 63% mature segmented neutrophils with normal granules and no blasts. What is the most likely explanation?

Inherited myeloperoxidase deficiency

Blasts missed on the blood film

Failure of the peroxidase reagent

Neutrophil aging in a delayed sample

The impedance platelet histogram is from a sample with an MCV of 57 fL; the film shows marked microcytosis and no platelet clumps. What should be done before the platelet count is reported?

Check it with an optical count or film estimate

Report the impedance count without comment

Recollect the sample in sodium citrate

Warm the sample to 37 °C and rerun

A patient with sepsis has a CBC that the analyzer flags for immature granulocytes and left shift. What should be done before the differential is released?

Review a Wright-stained blood film

Cell counts: automated

12 ASCP MLS practice questions on Cell counts: automated, part of Hematology. The first 12 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Hard
A healthy 47-year-old man has a routine CBC on an analyzer that sorts white cells by light scatter after a cytochemical peroxidase stain and also has a separate lobularity channel. Results: WBC 6.9 × 10^3/µL (6.9 × 10^9/L); peroxidase channel: neutrophils 5%, lymphocytes 31%, monocytes 4%, eosinophils 2%, large peroxidase-negative cells 58%. The lobularity channel counts 64% polymorphonuclear cells. Hemoglobin and platelets are normal, the sample is 2 hours old, and the controls and other patients on the run are normal. The blood film shows 63% mature segmented neutrophils with normal granules and no blasts. What is the most likely explanation?
1. ABlasts missed on the blood film
2. BFailure of the peroxidase reagent
3. CInherited myeloperoxidase deficiency
4. DNeutrophil aging in a delayed sample
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Answer: C · Inherited myeloperoxidase deficiency
The two channels disagree: the lobularity channel and the film both show about 63% normal segmented neutrophils, but the peroxidase channel places these cells among the large peroxidase-negative cells. Neutrophils that lack myeloperoxidase do not take up the stain, so they fall in the region the analyzer uses for blasts and atypical lymphocytes. Eosinophils use a different enzyme, eosinophil peroxidase, so they still stain, which fits inherited myeloperoxidase deficiency, a common and usually harmless trait. Blasts are excluded by the film, a delayed sample by the 2-hour age, and a reagent fault by the normal controls and other patients. Report the film differential with a comment so the finding is not mistaken for leukemia.
- A: The film shows mature neutrophils and no blasts, in agreement with the lobularity channel.
- B: A reagent fault would also affect the controls and the other patients on the run.
- D: The sample is only 2 hours old, and aging does not remove peroxidase from every neutrophil.
Question 2 · Medium
The impedance WBC histogram is from a 24-year-old with sickle cell anemia, and the analyzer flags the region below 35 fL. The film shows target cells and sickle cells, with no nRBCs or platelet clumps. The extra peak is most likely caused by:
Figure: MedExams
1. ANucleated red cells
2. BSmall mature lymphocytes
3. CPlatelet clumps
4. DRed cells that resisted lysis
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Answer: D · Red cells that resisted lysis
In a three-part impedance differential, lysed white cells are sized: lymphocytes about 35-90 fL, mid cells 90-160 fL and granulocytes above 160 fL. A peak that starts below 35 fL and does not return to the baseline at that threshold means small particles are being counted in the WBC channel. With nRBCs and platelet clumps excluded on the film, the cause here is red cells that resist lysis, as Hb S and Hb C cells and target cells may do. The WBC count may be falsely high; a rerun with longer lysis or a manual count gives the true value.
- A: The film shows no nRBCs.
- B: Lymphocytes, even small ones, size above the 35 fL threshold.
- C: The film shows no platelet clumps.
Question 3 · Medium
The impedance platelet histogram is from a sample with an MCV of 57 fL; the film shows marked microcytosis and no platelet clumps. What should be done before the platelet count is reported?
Figure: MedExams
1. ACheck it with an optical count or film estimate
2. BReport the impedance count without comment
3. CRecollect the sample in sodium citrate
4. DWarm the sample to 37 °C and rerun
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Answer: A · Check it with an optical count or film estimate
A normal platelet histogram returns to the baseline before the upper discriminator at about 20 fL. Here the curve dips and then rises again toward 20-30 fL, because very small red cells fall into the platelet size range and are counted as platelets, so the impedance count is falsely high. The count should be checked by an optical or fluorescent platelet count, or by a film estimate, before it is released. Recollection in citrate is for EDTA-induced clumping, and warming is for cold agglutinins.
- B: Microcytes falsely raise the impedance count, so it must be checked first.
- C: Citrate recollection corrects EDTA clumping, and the film shows no clumps.
- D: Warming corrects cold agglutinins, which affect the red cell count.
Question 4 · Easy
In the electrical impedance (Coulter) method, the height of each voltage pulse is proportional to the cell's:
1. AVolume
2. BNuclear density
3. CGranularity
4. DHemoglobin content
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Answer: A · Volume
Cells in an electrolyte diluent pass one at a time through a small aperture with an electrode on each side. Each cell is a poor conductor, so it briefly raises the resistance and creates a voltage pulse. The number of pulses gives the count, and the height of each pulse is proportional to cell volume. Pulse heights are plotted as size histograms, from which the analyzer derives the MCV.
- B: Impedance measures size only; nuclear features need optical or fluorescence methods.
- C: Granularity is measured by side-scattered light in optical systems.
- D: Hemoglobin is measured by photometry on lysed blood, not by pulse height.
Question 5 · Medium
A patient with sepsis has a CBC that the analyzer flags for immature granulocytes and left shift. What should be done before the differential is released?
1. AReview a Wright-stained blood film
2. BRecollect it in sodium citrate
3. CWarm the sample and rerun it
4. DRelease it with a comment
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Answer: A · Review a Wright-stained blood film
Suspect flags mean the analyzer has detected cells it cannot classify with confidence, such as bands, metamyelocytes or blasts. The lab's review criteria then require a film review and, where needed, a manual differential. The automated differential is released only after the film agrees with it. Flags are screening signals, not a final identification.
- B: Citrate recollection is used for EDTA-dependent platelet clumping.
- C: Warming corrects cold agglutinins and cryoglobulins, not immature cells.
- D: A comment does not replace checking what the flagged cells are.
Question 6 · Medium
A patient with iron deficiency anemia received two units of red cells yesterday. Which RBC histogram pattern is expected today?
1. ATwo peaks, one microcytic and one normocytic
2. BA single peak with a raised right tail
3. CA single peak shifted to the right
4. DA single peak shifted to the left
Answer and explanation in LearnFree account
Question 7 · Medium
In a three-part impedance differential, the lysing reagent collapses each white cell's cytoplasm around the nucleus. The cells are then sorted by their:
1. APeroxidase activity
2. BNucleic acid fluorescence
3. CSide-scatter signal
4. DSize after lysis
Answer and explanation in LearnFree account
Question 8 · Hard
A blood film shows many schistocytes and microspherocytes. The impedance platelet count is 186 × 10^3/µL (186 × 10^9/L) and the optical (fluorescent) platelet count is 74 × 10^3/µL (74 × 10^9/L). Which count should be reported, and why?
1. AOptical; impedance counts red cell fragments as platelets
2. BImpedance; fragments are too large to fall in the platelet range
3. COptical; impedance counts platelet clumps as red cells
4. DImpedance; optical methods miss the smallest platelets
Answer and explanation in LearnFree account
Question 9 · Easy
What is the purpose of hydrodynamic focusing in a hematology analyzer?
1. AStain reticulocyte RNA before counting
2. BSend cells past the sensor one at a time
3. CSeparate plasma proteins from the cells
4. DLyse red cells before the WBC count
Answer and explanation in LearnFree account
Question 10 · Easy
On an optical hematology analyzer, side-scattered laser light mainly gives information about a cell's:
1. AInternal granularity
2. BSurface antigen density
3. COverall cell size
4. DNucleic acid content
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Question 11 · Hard
A WBC count is above the analyzer's reportable range. One volume of blood is mixed with four volumes of diluent and rerun, and the analyzer now reads 38.6 × 10^3/µL. What WBC should be reported?
1. A38.6 × 10^3/µL (38.6 × 10^9/L)
2. B232 × 10^3/µL (232 × 10^9/L)
3. C154 × 10^3/µL (154 × 10^9/L)
4. D193 × 10^3/µL (193 × 10^9/L)
Answer and explanation in LearnFree account
Question 12 · Easy
Which anticoagulant is used for a routine complete blood count?
1. ALithium heparin
2. BSodium citrate
3. CK2EDTA
4. DSodium fluoride
Answer and explanation in LearnFree account

Cell counts: automated

The impedance WBC histogram is from a 24-year-old with sickle cell anemia, and the analyzer flags the region below 35 fL. The film shows target cells and sickle cells, with no nRBCs or platelet clumps. The extra peak is most likely caused by:

The impedance platelet histogram is from a sample with an MCV of 57 fL; the film shows marked microcytosis and no platelet clumps. What should be done before the platelet count is reported?

In the electrical impedance (Coulter) method, the height of each voltage pulse is proportional to the cell's:

A patient with sepsis has a CBC that the analyzer flags for immature granulocytes and left shift. What should be done before the differential is released?

A patient with iron deficiency anemia received two units of red cells yesterday. Which RBC histogram pattern is expected today?

In a three-part impedance differential, the lysing reagent collapses each white cell's cytoplasm around the nucleus. The cells are then sorted by their:

A blood film shows many schistocytes and microspherocytes. The impedance platelet count is 186 × 10^3/µL (186 × 10^9/L) and the optical (fluorescent) platelet count is 74 × 10^3/µL (74 × 10^9/L). Which count should be reported, and why?

What is the purpose of hydrodynamic focusing in a hematology analyzer?

On an optical hematology analyzer, side-scattered laser light mainly gives information about a cell's:

A WBC count is above the analyzer's reportable range. One volume of blood is mixed with four volumes of diluent and rerun, and the analyzer now reads 38.6 × 10^3/µL. What WBC should be reported?

Which anticoagulant is used for a routine complete blood count?