1 BASIC HEMATOLOGY CONCEPTS AND LABORATORY PROCEDURES

Question 1

(1) Insufficient centrifugation will result in:

A. A false increase in hematocrit (Hct) value
B. A false decrease in Hct value
C. No effect on Hct value
D. All of these options, depending on the patient

Answer 1

A. A false increase in hematocrit (Hct) value

Insufficient centrifugation does not pack down RBCs; therefore, the Hct, which is the volume of packed cells, will increase.

Question 2

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

A. Anisocytosis
B. Hypochromia
C. Poikilocytosis
D. Pleocytosis

Answer 2

A. Anisocytosis

A mature erythrocyte is approximately 7 to 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 RBC shape.

Question 3

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

A. Iliac crest
B. Sternum
C. Tibia
D. Spinous processes of a vertebra

Answer 3

A. Iliac crest

The iliac crest is the most frequently used site for bone marrow aspiration and biopsy. This site is the safest and most easily accessible, with the bone being just beneath the skin, and neither blood vessels nor nerves are in the vicinity

Question 4

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

A. (Hgb ÷ RBC) × 10 where Hgb is hemoglobin in g/dL
B. (Hct ÷ RBC) × 10
C. (Hct ÷ Hgb) × 100
D. (Hgb ÷ RBC) × 100

Answer 4

B. (Hct ÷ RBC) × 10

MCV is the average “volume” of the RBCs. This is obtained by dividing the Hct or packed cell volume (PCV) by the RBC count in millions per microliter (μL) of blood and multiplying by 10. MCV is expressed in cubic microns (μm^3) or femtoliters (fL).

Question 5

(5) 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

Answer 5

A. Poikilocytosis

Variation in the shape of erythrocytes on a peripheral blood smear is called poikilocytosis. Anisocytosis refers to change in size. Hypochromia is increase in central pallor in erythrocytes. Polychromasia describes the bluish tinge of the immature erythrocytes (reticulocytes) circulating in peripheral blood.

Question 6

(6) Calculate the mean cell hemoglobin concentration (MCHC) by using the following values:
Hgb: 15 g/dL (150 g/L)
Hct: 47 mL/dL (0.47)
RBC: 4.50 × 10^6/µL (4.50 × 10^12/L)

A. 9.5% (0.095)
B. 10.4% (0.104)
C. 31.9% (0.319)
D. 33.3% (0.333)

Answer 6

C. 31.9% (0.319)

MCHC is the average concentration of Hgb in RBCs expressed as a percentage. It expresses the ratio of the weight of Hgb to the volume of erythrocytes and is calculated by dividing Hgb by Hct and then multiplying by 100. A decrease in MCHC indicates that cells are hypochromic. In this example, (15 ÷ 47) × 100 = 31.9%. The reference range for MCHC is 32% to 36%.

Question 7

(7) A manual white blood cell (WBC) count was performed. In total 36 cells were counted in
all 9-mm^2 squares of a Neubauer-ruled hemacytometer. A 1:10 dilution was used. What is the WBC count?

A. 0.4 × 10^9/L
B. 2.5 × 10^9/L
C. 4.0 × 10^9/L
D. 8.0 × 10^9/L

Answer 7

A. 0.4 × 10^9/L

The formula used for calculating manual cell counts by using a hemacytometer is: Number of cells counted × dilution factor × depth factor (10) ÷ area. In this example, 36 × 10 × 10 = 3600 ÷ 9 = 400/mm^3 or 0.4 × 10^9/L.

Question 8

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

A. Spherocyte
B. Leptocyte
C. Schistocyte
D. Siderocyte

Answer 8

D. Siderocyte

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

Question 9

(9) 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

Answer 9

C. Hct

Excessive anticoagulant causes shrinkage of cells; thus, Hct will be affected. RBC and WBC counts remain the same, as does the Hgb content.

Question 10

(10) A 1:200 dilution of a patient’s sample was made, and 336 RBCs were counted in an area
of 0.2 mm^2. What is the RBC count?

A. 1.68 × 10^12/L
B. 3.36 × 10^12/L
C. 4.47 × 10^12/L
D. 6.66 × 10^12/L

Answer 10

B. 3.36 × 10^12/L

RBC count = number of cells counted × dilution factor × depth factor (10), ÷ area. In this example, 336 × 200 × 10 = 672,000 ÷ 0.2 = 3.36 × 10^6/mm^3 = 3.36 × 10^12/L.

Question 11

(11) What phagocytic cells produce lysozymes that are bacteriocidal?

A. Eosinophils
B. Lymphocytes
C. Platelets (PLTs)
D. Neutrophils

Answer 11

D. Neutrophils

Neutrophils are highly phagocytic and release lysozymes, peroxidase, and pyrogenic proteins. Eosinophils migrate to sites where there is an allergic reaction or parasitic infestation and release peroxidase, pyrogens, and other enzymes, including an oxidase that neutralizes histamine. Eosinophils are poorly phagocytic and do not release lysozyme

Question 12

(12) 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%

Answer 12

B. 3.1%

In anemic states, the reticulocyte percentage is not a true measure of reticulocyte production. The following formula must be applied to calculate the corrected (for anemia) reticulocyte count. Corrected reticulocyte count = reticulocytes (%) × (Hct ÷ 45) where 45 is the average normal Hct. In this case, 7 × (20 ÷ 45) = 3.1.

Question 13

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

A. Sickle cell anemia
B. Hereditary spherocytosis (HS)
C. Hemolytic disease of the fetus and newborn
D. Acquired hemolytic anemia

Answer 13

A. Sickle cell anemia

Osmotic fragility is decreased when numerous sickle cells and target cells are present and is increased in the presence of spherocytes. Spherocytes are a prominent feature of HS, hemolytic disease of the fetus and newborn, and acquired hemolytic anemia. The osmotic fragility test reveals an increase in the presence of spherocytes, whereas a decrease is seen when sickle cells, target cells, and other poikilocytes are present.

Question 14

(14) 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

Answer 14

A. RBCs would be stained too pink

The pH of the buffer is critical in Romanowsky staining. When the pH is too low (less than 6.4), the RBCs take up more acid dye (eosin), becoming too pink. Leukocytes also show poor nuclear detail when the pH is decreased.

Question 15

(15) 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

Answer 15

B. Heinz bodies

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

Question 16

(16) . A falsely elevated Hct is obtained. Which of the following calculated values will not be affected?

A. MCV
B. Mean corpuscular hemoglobin (MCH)
C. MCHC
D. Red blood cell distribution width (RDW)

Answer 16

B. Mean corpuscular hemoglobin (MCH)

MCH = Hgb × 10/RBC count and is not affected by Hct. MCV = Hct × 10/RBC count, and MCHC = Hgb × 100/Hct; therefore, an erroneous Hct will affect these parameters. Centrifugal force for microhematocrit determination should be 12,000 g
for 5 minutes to avoid errors caused by trapped plasma. RDW is calculated by using electronic cell counters and reflects the variance in the size of the RBC population. Electronic cell counters calculate Hct from MCV and RBC count. Therefore, RDW would be affected by an erroneous MCV.

Question 17

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

A. PLT
B. Reticulocytes
C. Sickle cells
D. Nucleated red blood cells (NRBCs)

Answer 17

B. Reticulocytes

The manual reticulocyte count involves the counting of 1,000 RBCs. The Miller disk is a reticle (grid) that is placed in the eyepiece of the microscope and divides the field into two squares, one being nine times larger in size than the other. Reticulocytes are enumerated in both the squares. Mature RBCs are counted in the smaller one.

Question 18

(18) SITUATION: RBC indices obtained on an anemic patient are as follows: MCV 88 μm^3
(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

Answer 18

C. Normocytic, normochromic

MCV, MCH, and MCHC are all within the reference interval (normal range); hence, the erythrocytes should be of normal size and should reflect normal concentrations of Hgb. Therefore, the anemia is normocytic normochromic.

Question 19

(19) 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

Answer 19

A. Blood drawn into a sodium citrate tube

EDTA and sodium citrate can be used without any effect on the ESR. Anisocytosis and poikilocytosis may impede rouleaux formation, thus causing a low ESR. Plasma proteins, especially fibrinogen and immunoglobulins, enhance rouleaux, increasing the ESR. Reference ranges must be established for tubes of different calibers.

Question 20

(20) What staining method is used most frequently to stain and manually count reticulocytes?

A. Immunofluorescence
B. Supravital staining
C. Romanowsky staining
D. Cytochemical staining

Answer 20

B. Supravital staining

The reticulum within reticulocytes consists of ribonucleic acid (RNA), which cannot be stained with Wright stain. Supravital staining with new methylene blue is used to identify reticulocytes.

Question 21

(21) 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

Answer 21

A. Isotonic solutions conduct electricity better than cells do

Electronic cell (Coulter) counters use the principle of electrical impedance. Two electrodes suspended in isotonic solutions are separated by a glass tube that has 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.

Question 22

(22) 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

Answer 22

C. NRBCs are counted as leukocytes

Automated hematology analyzers enumerate all nucleated cells. NRBCs are counted along with WBCs, falsely elevating the WBC count. To correct the WBC count, the number of NRBCs per 100 WBCs should be determined. Corrected WBC count = (uncorrected WBC count ÷ [NRBC’s + 100]) × 100.

Question 23

(23) Using an electronic cell counter analyzer, an increased RDW should correlate with:

A. Spherocytosis
B. Anisocytosis
C. Leukocytosis
D. Presence of NRBCs

Answer 23

B. Anisocytosis

The RDW parameter correlates with the degree of anisocytosis seen on the morphological examination. The reference range is 11.5% to 14.5%

Question 24

(24) Given the following values, which set of RBC indices suggests spherocytosis?

A. MCV 76 μm^3 MCH 19.9 pg MCHC 28.5%
B. MCV 90 μm^3 MCH 30.5 pg MCHC 32.5%
C. MCV 80 μm^3 MCH 36.5 pg MCHC 39.0%
D. MCV 81 μm^3 MCH 29.0 pg MCHC 34.8%

Answer 24

C. MCV 80 μm^3 MCH 36.5 pg MCHC 39.0%

Spherocytes have decreased cell diameter and volume, and this results in loss of central pallor and discoid shape. The index most affected is MCHC, usually being in excess of 36%.

Question 25

(25) 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

Answer 25

C. Coefficient of variation

Standard deviation(s) describes the distribution of a sample of observations. It depends on the dispersion of results and is most influenced by reproducibility or precision. Because s is influenced by the mean, the coefficient of variation ([s ÷ mean]
× 100) can be used to compare precision of tests with different means (e.g., WBC and RBC counts or low vs. high controls).

Question 26

(26) Which of the following is considered a normal Hgb?

A. Carboxyhemoglobin
B. Methemoglobin
C. Sulfhemoglobin
D. Deoxyhemoglobin

Answer 26

D. Deoxyhemoglobin

Deoxyhemoglobin is the physiological Hgb that results from the unloading of O2 by Hgb. This is accompanied by the widening of the space between β-chains and the binding of 2,3 diphosphoglycerate (2,3-DPG) on a mole-for-mole basis.

Question 27

(27) 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

Answer 27

A. Acidosis

Acidosis is associated with a shift to the right of the oxyhemoglobin dissociation curve and, therefore, increased O2 release (decreased affinity of Hgb for O2). Alkalosis does the opposite. Multiple blood transfusions shift the curve to the left because
transfused blood is low in 2,3-DPG. Hgb S and Hgb C do not change the affinity of O2 for Hgb; however, many hemoglobinopathies do. For example, Hgb Kansas causes a right shift, and Hgb Chesapeake causes a left shift of the oxyhemoglobin dissociation curve.

Question 28

(28) 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

Answer 28

B. Lymphocyte

In aplastic anemia, lymphocytes constitute the majority of the nucleated cells seen. In aplastic anemia, bone marrow is spotty, with patches of normal cellularity. Absolute granulocytopenia is usually present; however, lymphocyte production is less affected.

Question 29

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%

Answer 29

C. 20%–44%

The normal adult percentage of lymphocytes in a WBC differential is between 20% and 44%, although normal ranges vary by institution, patient population, and testing methodology. This range is higher in the pediatric population.

Question 30

(30) 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

Answer 30

A. 6 months–2 years

There is relative neutropenia in children from ages 4 months to 4 years. Because of this, the percentage of lymphocytes is increased in this population. This is commonly referred to as a reversal in the normal differential percentage (or inverted differential).

Question 31

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

A. Segs = 70%
B. Band = 6%
C. Mono = 15%
D. Eos = 2%

Answer 31

C. Mono = 15%

A relative monocyte count of 15% is abnormal, given that the baseline monocyte count in a normal differential is between 1% and 8%. An increased monocyte count may signal a myeloproliferative process, such as chronic myelomonocytic leukemia, an inflammatory response, or abnormal lymphocytes that may have been counted as monocytes by an automated cell counter.

Question 32

(32) 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

Answer 32

D. Polychromatic normoblast

In normal erythrocytic maturation, Hgb formation in the late polychromatic normoblast stage gives the cytoplasm a prominent pink coloration. The RBC continues to produce Hgb throughout the reticulocyte stage of development.

Question 33

(33) 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

Answer 33

D. All of these options

Increases in 2,3-DPG, acidosis, and hypoxia and rise in body temperature all shift the Hgb O2 dissociation curve to the right. In anemia, although the number of RBCs is reduced, the cells are more efficient at O2 delivery because there is an increase in RBC 2,3-DPG. This causes the oxyhemoglobin dissociation curve to shift to the right, allowing more O2 to be released to tissues.

Question 34

(34) Which of the following Hgb configurations is characteristic of Hgb H?

A. γ4
B. α2-γ2
C. β4
D. α2-β2

Answer 34

C. β4

The structure of Hgb H is β4. Hgb H disease is a severe clinical expression of αthalassemia in which only one α-gene out of four is functioning.

Question 35

(35) 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

Answer 35

D. All of these options

Autoagglutination at room temperature may cause a low RBC count and high MCV from an electronic counter. The Hct will be low because it is calculated from the RBC count. Low RBC count and low Hct cause falsely high values of MCH and MCHC, respectively.