1.1 - Basic Hematology Concepts and Laboratory Procedures

Insufficient centrifugation will result in:

A. A false increase in hematocrit (Hct) value

B. A false decrease in Hct value

C. No effect of Hct value

D. All of these options, depending on the patient

A. A false increase in hematocrit (Hct) value

Variation in red blood cell (RBC) size observed on the peripheral blood smear is described as:

A. Anisocytosis

B. Hypochromia

C. Poikilocytosis

D. Pleocytosis

A. Anisocytosis

Which of the following is the preferred site for bone marrow aspiration and biopsy in adult?

A. Iliac crest

B. Sternum

C. Tibia

D. Spinous process of a vertebra

A. Iliac crest

Mean cell volume (MCV) is calculated by using the following formula:

A. (Hgb / RBC) x 10, where Hgb is hemoglobin in g/dL

B. (Hct / RBC) x 10

C. (Hct / Hgb) x 100

D. (Hgb / RBC) x 100

B. (Hct / RBC) x 10

What term describes the change in shape of erythrocytes seen on a Wright-stained peripheral blood smear?

A. Poikilocytosis

B. Anisocytosis

C. Hypochromia

D. Polychromasia

A. Poikilocytosis

Calculate the mean cell hemoglobin concentration (MCHC) by using the following values:

Hgb: 15 g/dL (150 g/dL)

Hct: 47 mL/dL (0.47)

RBC: 4.50 x 10^6/uL (4.50 x 10^12/L)

A. 9.5% (0.095)

B. 10.4% (0.104)

C. 31.9% (0.319)

D. 33.3% (0.333)

C. 31.9% (0.319)

(Hgb / Hct) x 100

A manual white blood cell (WBC) count was performed. In total, 36 cells were counted in all 9-mm2 squares of a Neubauer-ruled hemacytometer. A 1:10 dilution was used. What is the WBC count?

A. 0.4 x 10^9/L

B. 2.5 x 10^9/L

C. 4.0 x 10^9/L

D. 8.0 x 10^9/L

A. 0.4 x 10^9/L

Cells counted x dilution / volume in ul
36 × 10 / (0.1 × 09) = 400 ul

400 × 10⁶ / 10⁹ = 0.4 × 10⁹

When an erythrocyte containing iron granules is stained with Prussian blue, the cell is called a:

A. Spherocyte

B. Leptocyte

C. Schistocyte

D. Siderocyte

D. Siderocyte

A 7.0-mL ethylenediaminetetraacetic acid (EDTA) tube is received in the laboratory containing only 2.0 mL of blood. If the laboratory is using manual techniques, which of the following tests will most likely be erroneous?

A. RBC count

B. Hgb

C. Hct

D. WBC count

C. Hct

• Reasoning: Underfilled EDTA tubes cause excess anticoagulant (EDTA) relative to blood volume, leading to cellular shrinkage from osmotic effects. This produces a falsely low hematocrit when measured manually by microhematocrit or calculated from MCV × RBC.

• Context:

  • Hgb (colorimetric) and cell counts (RBC/WBC) are minimally affected.

  • Hct depends directly on cell size and packing, which EDTA alters.

• Key takeaway:

  • Underfilled EDTA → RBC shrinkage → ↓Hct (falsely low).

A 1:200 dilution of a patient's sample was made and 336 RBCs were counted in an area of 0.2 mm2. What is the RBC count?

A. 1.68 x 10^12/L

B. 3.36 x 10^12/L

C. 4.47 x 10^12/L

D. 6.66 x 10^12/L

B. 3.36 x 10^12/L

RBC x depth × dilution factor / 2 squares

Volume = area x depth

V = 0.2 × 0.1 = 0.02

cells x dilution factors / depth

336 × 200 / 0.02 = 3,360,000 ul
to convert to 10¹²/L multiple 3.36 × 10⁶ × 10⁶ = 3.36 × 10¹²

What phagocytic cells produce lysozymes that are bacteriocidal?

A. Eosinophils

B. Lymphocytes

C. Platelets (PLTs)

D. Neutrophils

D. Neutrophils

If a patient has a reticulocyte count of 7% and Hct of 20%, what is the corrected reticulocyte count?

A. 1.4%

B. 3.1%

C. 3.5%

D. 14%

B. 3.1%

Corrected retic count = retic % x (Hct / 45)

A decreased osmotic fragility test would be associated with which of the following conditions?

A. Sickle cell anemia

B. Hereditary spherocytosis

C. Hemolytic disease of the fetus and newborn

D. Acquired hemolytic anemia

A. Sickle cell anemia

• Reasoning: Decreased osmotic fragility means RBCs are more resistant to hemolysis in hypotonic saline—they tolerate lower salt concentrations before rupturing.

• Context:

  • Sickle cells (and target cells in thalassemia) have increased surface-to-volume ratio, making them less fragile.

  • In contrast, spherocytes (HS, HDFN, acquired hemolysis) have decreased surface area, causing increased fragility (lyse earlier).

• Key takeaway:

  • ↓ Osmotic fragility → sickle cell, thalassemia

  • ↑ Osmotic fragility → spherocytosis, HDFN.

What effect would using a buffer at pH 6.0 have on a Wright-stained smear?

A. RBCs would be stained too pink

B. WBC cytoplasm would be stained too blue

C. RBCs would be stained too blue

D. RBCs would lyse on the slide

A. RBCs would be stained too pink

• Reasoning: Wright stain depends on a buffer pH of ~6.4–6.8 for proper color balance between acidic (eosin) and basic (methylene blue) dyes.

• Effect of pH 6.0 (too acidic):

  • The acidic environment enhances eosin binding, so RBCs and eosinophilic granules become overly pink/red, while WBC cytoplasm and nuclei appear pale or washed out.

• Key takeaway:

  • Acidic buffer → overly pink smear

  • Alkaline buffer → overly blue smear

Which of the following erythrocyte inclusions can be visualized with supravital stain but cannot be detected on a Wright-stained blood smear?

A. Basophilic stippling

B. Heinz bodies

C. Howell-Jolly bodies

D. Siderotic granules

B. Heinz bodies

A falsely elevated Hct is obtained. Which of the following calculated values will NOT be affected?

A. MCV

B. MCH

C. MCHC

D. Red blood cell distribution width (RDW)

B. MCH

• Reasoning: MCH depends only on Hgb and RBC count — not on hematocrit.

  • Formula: MCH = (Hgb × 10) ÷ RBC

• Context:

  • A falsely high Hct would artificially increase MCV and decrease MCHC, but MCH remains unchanged.

Index	Formula	Uses Hct?	Effect if Hct falsely ↑
MCV	(Hct ÷ RBC) × 10	✅ Yes	↑ falsely
MCH	(Hb ÷ RBC) × 10	❌ No	❌ unaffected
MCHC	(Hb ÷ Hct) × 100	✅ Yes	↓ falsely
RDW	Statistical measure of RBC size variation (from cell volume histogram)	❌ No (derived from measuredRBC sizes)	❌ unaffected

A Miller disk is an ocular device used to facilitate counting of:

A. PLT

B. Reticulocytes

C. Sickle cells

D. Uncleared red blood cells (NRBCs)

B. Reticulocytes

RBC indices obtained on an anemic patient are as follows:

MCV = 88 um3 (fL)

MCH = 30 pg

MCHC = 34% (0.340).

The RBCs on the peripheral blood smear would appear:

A. Microcytic, hypochromic

B. Microcytic, normochromic

C. Normocytic, normochromic

D. Normocytic, hypochromic

C. Normocytic, normochromic

All of the following factors may influence the erythrocyte sedimentation rate (ESR) except:

A. Blood drawn into a sodium citrate tube

B. Anisocytosis, Poikilocytosis

C. Plasma proteins

D. Caliber of the tube

A. Blood drawn into a sodium citrate tube

• Reasoning: ESR must be measured in EDTA-anticoagulated whole blood (or citrated blood only if specifically adjusted). Using sodium citrate without correcting the dilution alters plasma-to-cell ratio, giving an invalid ESR rather than a physiologic change.

• Context: Factors that do influence ESR include:

  • RBC morphology (anisocytosis/poikilocytosis → ↓ ESR)

  • Plasma proteins (↑ fibrinogen, globulins → ↑ ESR)

  • Tube diameter (wider → faster settling).

• Key takeaway:

  • Specimen type itself (sodium citrate) doesn’t physiologically change ESR—it’s a preanalytical error, not a true influencing factor.

What staining method is used most frequently to stain and manually count Reticulocytes?

A. Immunofluorescence

B. Supravital staining

C. Romanowsky staining

D. Cytochemical staining

B. Supravital staining

• Reasoning: Reticulocytes contain residual RNA, which must be stained while the cells are still alive (unfixed)—that’s what supravital stains do.

• Common stains: New methylene blue or brilliant cresyl blue form a dark blue reticulum (RNA precipitate).

• Key takeaway:

  • Supravital = stain living cells

  • Used for reticulocyte counts to assess marrow RBC production.

The Coulter principle for counting of cells is based on the fact that:

A. Isotonic solutions conduct electricity better than cells do

B. Conductivity varies proportionally to the number of cells

C. Cells conduct electricity better than saline does

D. Isotonic solutions cannot conduct electricity

A. Isotonic solutions conduct electricity better than cells do

• Reasoning: The Coulter principle (electrical impedance method) measures changes in electrical resistance as cells pass through a small aperture in an electrolyte solution.

• Mechanism:

  • The electrolyte (saline) conducts electricity.

  • Each cell is a poor conductor, briefly increasing resistance as it passes the aperture.

  • The number of pulses = cell count, and pulse size = cell volume.

• Key takeaway:

  • Cells = poor conductors → impedance spikes.

  • Coulter principle = counts + sizes cells by resistance change.

A correction is necessary for WBC counts when NRBCs are seen on the peripheral blood smear because:

A. The WBC count would be falsely lower

B. The RBC count is too low

C. NRBCs are counted as leukocytes

D. NRBCs are confused with giant PLTs

C. NRBCs are counted as leukocytes

Given the following values, which set of RBC indices suggest spherocytosis?

A. MCV: 76 fL, MCH: 19.9 pg, MCHC: 28.5%

B. MCV: 90 fL, MCH: 30.5 pg, MCHC: 32.5%

C. MCV: 80 fL, MCH: 36.5 pg, MCHC: 39.0%

D. MCV: 81 fL, MCH: 29.0 pg, MCHC: 34.8%

C. MCV: 80 fL, MCH: 36.5 pg, MCHC: 39.0%

Which of the following statistical terms reflects the best index of precision when comparing two complete blood count (CBC) parameters?

A. Mean

B. Median

C. Coefficient of variation

D. Standard deviation

C. Coefficient of variation

• Reasoning: The CV expresses precision by relating the standard deviation (SD) to the mean, allowing comparison between different parameters or instruments.

  • Formula: CV (%) = (SD ÷ Mean) × 100

• Context:

  • Low CV → high precision

  • SD alone doesn’t account for magnitude of the mean, so CV is preferred for comparing precision across CBC parameters (e.g., Hgb vs RBC).

• Key takeaway:

  • Best index of precision = Coefficient of variation (CV).

Which of the following is considered a normal Hgb?

A. Carboxyhemoglobin

B. Methemoglobin

C. Sulfhemoglobin

D. Deoxyhemoglobin

D. Deoxyhemoglobin

• Reasoning: Deoxyhemoglobin is physiologically normal, representing hemoglobin that has released its oxygen to tissues but can still bind oxygen reversibly.

• Context:

  • Carboxyhemoglobin → CO bound; cannot carry O₂ (toxic)

  • Methemoglobin → Iron oxidized to Fe³⁺; cannot bind O₂

  • Sulfhemoglobin → Irreversibly altered; cannot bind O₂

• Key takeaway:

  • Normal, functional hemoglobins: oxyhemoglobin + deoxyhemoglobin

  • Others are dysfunctional or pathologic derivatives.

Which condition will shift the oxyhemoglobin dissociation curve to the right?

A. Acidosis

B. Alkalosis

C. Multiple blood transfusions

D. Increased quantities of Hgb S or C

A. Acidosis

• Reasoning: Right shift = decreased O₂ affinity, meaning hemoglobin releases oxygen more easily to tissues.

• Causes of a right shift:

  • ↓ pH (acidosis)

  • ↑ temperature

  • ↑ pCO₂

  • ↑ 2,3-BPG

• Context: Alkalosis shifts the curve left (↑ O₂ affinity), while transfusions or Hb variants can have variable effects depending on storage or structure.

• Key takeaway:

  • Right shift → O₂ release favored (acidosis, heat, CO₂, 2,3-BPG).

  • Left shift → O₂ binding favored (alkalosis, cold, ↓ CO₂).

What is the major type of leukocyte seen in the peripheral blood smear from a patient with aplastic anemia?

A. Segmented neutrophil

B. Lymphocyte

C. Monocyte

D. Eosinophil

B. Lymphocyte

• Reasoning: Aplastic anemia causes pancytopenia due to bone marrow failure—granulocytes, RBCs, and platelets are all decreased. Lymphocytes are relatively preserved because they originate partly from lymphoid tissues, not just bone marrow.

• Key takeaway:

  • Aplastic anemia → ↓ all cell lines, but lymphocytes remain proportionally increased.

  • Thus, the major leukocyte type seen = lymphocyte.

What is the normal WBC differential lymphocyte percentage (range) in the adult population?

A. 5 - 10%

B. 10 - 20%

C. 20 - 44%

D. 50 - 70%

C. 20 - 44%

In which age group would 60% lymphocytes be a normal finding?

A. 6 months - 2 years

B. 4 - 6 years

C. 11 - 15 years

D. 40 - 60 years

A. 6 months - 2 years

Which of the following results on an automated differential suggests that a peripheral blood smear should be reviewed manually?

A. Segs = 70%

B. Bands = 6%

C. Mono = 15%

D. Eos = 2%

C. Mono = 15%

• Reasoning: Normal monocyte range ≈ 2–10%. A monocytosis of 15% is outside reference limits and may indicate reactive or neoplastic changes (infection, inflammation, leukemia).

• Context: Automated differentials flag abnormal distributions or suspect populations (e.g., blasts, left shift), prompting manual smear review for morphology verification.

• Key takeaway:

  • Abnormal differential (mono >10%) → manual smear review required.

  • Other listed values (Segs 70%, Bands 6%, Eos 2%) fall within normal limits.

  • Normal range for bands (band neutrophils):0–10% of total WBCs

    • Context: Bands represent immature neutrophils released during increased demand.

    • >10% bands = "left shift", often seen in:

      • Bacterial infections

      • Inflammation

      • Myeloproliferative disorders

    • Key takeaway:

      • Normal: 0–10%

      • Abnormal (left shift): >10% bands or presence of earlier granulocytes (metamyelocytes, myelocytes).

Which is the first stage of erythrocytic maturation in which the cytoplasm is pink because of the formation of Hgb?

A. Reticulocyte

B. Pronormoblast

C. Basophilic normoblast

D. Polychromatic normoblast

D. Polychromatic normoblast

Which of the following can shift the Hgb oxygen (O2) dissociation curve to the right?

A. Increases in 2,3 DPG

B. Acidosis

C. Hypoxia

D. All of these options

D. All of these options

Which of the following Hgb configurations is characteristic of Hgb H?

A. Gamma 4

B. Alpha 2-gamma 2

C. Beta 4

D. Alpha 2-beta 2

C. Beta 4

• Hemoglobin H is composed of four beta chains (β₄) that form when alpha-globin synthesis is markedly reduced, leaving excess beta chains to aggregate.

• It appears in alpha-thalassemia (three-gene deletion) and causes microcytic, hypochromic anemia with the presence of Heinz bodies due to unstable hemoglobin.

Autoagglutination of RBCs at room temperature can cause which of the following abnormal test results?

A. Low RBC count

B. High MCV

C. Low Hct

D. All of these options

D. All of these options

Using an electronic cell counter analyzer, an increased RDW should correlate with.

A. Spherocytosis

B. Anisocytosis

C. Leukocytosis

D. Presence of nRBCs

B. Anisocytosis