Hematology Review

Variation in red cell size observed on the peripheral smear is described as:

• Anisocytosis

• Hypochromia

• Poikilocytosis

• Pleocytosis

Answer explanation

A mature erythrocyte is approximately 7–8 μm in diameter. Variation in normal size is denoted by the term anisocytosis. Hypochromia is a term that indicates increased central pallor in erythrocytes, and poikilocytosis denotes variation in red cell shape.

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

• (Hgb ÷ RBC) × 10

• (Hct ÷ RBC) × 10

• (Hct ÷ Hgb) × 100

• (Hgb ÷ RBC) × 100

Answer explanation

MCV is the average “volume” of the red cells. This is obtained by dividing the Hct or packed cell volume (PCV) by the red blood cell (RBC) count in millions per microliter of blood and multiplying by 10. The MCV is expressed in cubic microns (μm3) or femtoliters (fL).

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

• Spherocyte

• Leptocyte

• Schistocyte

• Siderocyte

Answer explanation

Siderocytes are red cells containing iron granules and are visible when stained with Prussian blue.

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

• Basophilic stippling

• Heinz bodies

• Howell–Jolly bodies

• Siderotic granules

Answer explanation

Heinz bodies are irregular, refractile, purple inclusions that are not visible with Wright’s stain but show up with supravital staining. The other three inclusions can be detected with Wright’s stain.

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

• Isotonic solutions conduct electricity better than cells do

• Conductivity varies proportionally to the number of cells

• Cells conduct electricity better than saline does

• Isotonic solutions cannot conduct electricity

Answer explanation

Electronic cell (Coulter) counters use the principle of electrical impedance. Two electrodes suspended in isotonic solutions are separated by a glass tube having a small aperture. A vacuum is applied, and as a cell passes through the aperture it impedes the flow of current and generates a voltage pulse.

Insufficient centrifugation will result in:

• A false increase in hematocrit (Hct) value

• A false decrease in Hct value

• No effect on Hct value

• All of these options, depending on the patient

Answer explanation

Insufficient centrifugation does not pack down the red blood cells; therefore, the Hct, which is the volume of packed cells, will increase. 2. A A mature erythrocyte is approximately

A manual white blood cell (WBC) count was performed. A total of 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?

• 0.4 × 109/L

• 2.5 × 109/L

• 4.0 × 109/L

• 8.0 × 109/L

Answer explanation

The formula used for calculating manual cell counts using a hemacytometer is: Number of cells counted × dilution factor × depth factor (10) divided by the area. In this example, 36 × 10 × 10 = 3600 ÷ 9 = 400/mm3or 0.4 × 109/L.

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

• 1.68 × 1012/L

• 3.36 × 1012/L

• 4.47 × 1012/L

• 6.66 × 1012/L

Answer explanation

RBC count = number of cells counted × dilution factor × depth factor (10), divided by the area. In this example, 336 × 200 × 10 = 672,000 ÷ 0.2 = 3.36 × 106/mm3 = 3.36 × 1012/L.

Iron deficiency anemia is characterized by:

• Decreased plasma iron, decreased % saturation, increased total iron-binding capacity (TIBC)

• Decreased plasma iron, decreased plasma ferritin, normal RBC porphyrin

• Decreased plasma iron, decreased % saturation, decreased TIBC

• Decreased plasma iron, increased % saturation, decreased TIBC

Answer explanation

Iron deficiency anemia is characterized by decreased plasma iron, increased TIBC, decreased % saturation, and microcytic, hypochromic anemia. Iron deficiency occurs in three phases: iron depletion, iron-deficient erythropoiesis, and iron deficiency anemia.

All of the following are characteristics of megaloblastic anemia except:

• Pancytopenia

• Elevated reticulocyte count

• Hypersegmented neutrophils

• Macrocytic erythrocyte indice

Answer explanation

Megaloblastic anemias are associated with an ineffective erythropoiesis and therefore a decrease in the reticulocyte count.