1.1 Hematology: 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 on Hct value

D. All of these options, depending on the patient

A. A false increase in hematocrit (Hct) value

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

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

A. Anisocytosis

B. Hypochromia

C. Poikilocytosis

D. Pleocytosis

A. Anisocytosis

A 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.

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

A. Iliac crest

B. Sternum

C. Tibia

D. Spinous processes of a vertebra

A. Iliac crest

A 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 just beneath the skin, and neither blood vessels nor nerves are in the vicinity.

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

A. (Hgb ÷ RBC) × 10

B. (Hct ÷ RBC) × 10

C. (Hct ÷ Hgb) × 100

D. (Hgb ÷ RBC) × 100

B. (Hct ÷ RBC) × 10

B 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).

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

A. Poikilocytosis

B. Anisocytosis

C. Hypochromia

D. Polychromasia

A. Poikilocytosis

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

Calculate the mean cell hemoglobin concentration

(MCHC) using the following values:

Hgb: 15 g/dL (150 g/L) Hct: 47 mL/dL (0.47)

RBC: 4.50 × 106/μL (4.50 × 1012/L)

A. 9.5% (.095)

B. 10.4% (.104)

C. 31.9% (.319)

D. 33.3% (.333)

C. 31.9% (.319)

C MCHC is the average concentration of Hgb in red cells 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 the Hct, and then multiplying by 100. A decreased MCHC indicates that cells are hypochromic. In this example, (15 ÷ 47) × 100 = 31.9%. The reference range for MCHC is 32%-36%.

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?

A. 0.4 × 109/L

B. 2.5 × 109/L

C. 4.0 × 109/L

D. 8.0 × 109/L

A. 0.4 × 109/L

A 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/mm3 or 0.4 × 109/L.

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

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

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. Hemoglobin (Hgb)

C. Hct

D. WBC count

C. Hct

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

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?

A. 1.68 × 1012/L

B. 3.36 × 1012/L

C. 4.47 × 1012/L

D. 6.66 × 1012/L

B. 3.36 × 1012/L

B 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

What phagocytic cells produce lysozymes that are bacteriocidal?

A. Eosinophils

B. Lymphocytes

C. Platelets

D. Neutrophils

D. Neutrophils

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

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

A. 1.4%

B. 3.1%

C. 3.5%

D. 14%

B. 3.1%

B 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, the average normal Hct. In this case, 7 × (20 ÷ 45) = 3.1.

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 newborn

D. Acquired hemolytic anemia

A. Sickle cell anemia

A 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 hereditary spherocytosis (HS), hemolytic disease of the newborn, and acquired hemolytic anemia. The osmotic fragility test is increased in the presence of spherocytes, whereas this test is decreased when sickle cells, target cells, and other poikilocytes are present.

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

A. Red cells would be stained too pink

B. White cell cytoplasm would be stained too blue

C. Red cells would be stained too blue

D. Red cells would lyse on the slide

A. Red cells would be stained too pink

A The pH of the buffer is critical in Romanowsky stains. When the pH is too low (<6.4), the red cells take up more acid dye (eosin), becoming too pink.

Leukocytes also show poor nuclear detail when the pH is decreased.

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

A. Basophilic stippling

B. Heinz bodies

C. Howell-Jolly bodies

D. Siderotic granules

B. Heinz bodies

B 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.

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

A. MCV

B. MCH

C. MCHC

D. Red cell distribution width (RDW)

B. MCH

The MCH = Hgb × 10/RBC count and is not affected by the Hct. The 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 min in order to avoid error caused by trapped plasma. The red cell distribution width (RDW) is calculated by electronic cell counters and reflects the variance in the size of the red cell population. Electronic cell counters calculate Hct from the MCV and RBC count. Therefore, the RDW would be affected by an erroneous MCV.

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

A. Platelets

B. Reticulocytes

C. Sickle cells

D. Nucleated red blood cells (NRBCs)

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 red cells are counted in the smaller one.

SITUATION: RBC indices obtained on an anemic patient are as follows:

MCV 88 µm3 (fL); MCH 30 pg; MCHC 34% (.340).

The RBCs on the peripheral smear would appear:

A. Microcytic, hypochromic

B. Microcytic, normochromic

C. Normocytic, normochromic

D. Normocytic, hypochromic

C. Normocytic, normochromic

C The 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

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

A 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 different caliber tubes

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

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

The Coulter principle for counting of cells is based upon 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

A 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.

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

A. The WBC count would be falsely lower

B. The RBC count is too low

C. Nucleated RBCs are counted as leukocytes

D. Nucleated RBCs are confused with giant platelets

C. Nucleated RBCs are counted as leukocytes

C The automated hematology analyzers enumerate all nucleated cells. NRBCs are counted along with WBCs, falsely elevating the WBC count. To correct the WBC count, determine the number of NRBCs per 100 WBCs. Corrected WBC count =(uncorrected WBC count ÷ [NRBC's + 100]) × 100.

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

A. Spherocytosis

B. Anisocytosis

C. Leukocytosis

D. Presence of NRBCs

B. Anisocytosis

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

Given the following values, which set of red blood cell indices suggests spherocytosis?

A. MCV 76 µm3 MCH 19.9 pg MCHC 28.5%

B. MCV 90 µm3 MCH 30.5 pg MCHC 32.5%

C. MCV 80 µm3 MCH 36.5 pg MCHC 39.0%

D. MCV 81 µm3 MCH 29.0 pg MCHC 34.8%

C. MCV 80 µm3 MCH 36.5 pg MCHC 39.0%

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

Which of the following statistical terms reflects the best index of precision when comparing two CBC parameters?

A. Mean

B. Median

C. Coefficient of variation

D. Standard deviation

C. Coefficient of variation

C Standard deviation(s) describes the distribution of a sample of observations. It depends upon both the mean (average value) and dispersion of results and is most influenced by reproducibility or precision. Because s is influenced by the mean and expressed as a percentage of 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).

Which of the following is considered a normal hemoglobin?

A. Carboxyhemoglobin

B. Methemoglobin

C. Sulfhemoglobin

D. Deoxyhemoglobin

D. Deoxyhemoglobin

D Deoxyhemoglobin is the physiological Hgb that results from the unloading of oxygen 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.

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

A. Acidosis

B. Alkalosis

C. Multiple blood transfusions

D. Increased quantities of hemoglobin S or C

A. Acidosis

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

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

A. Segmented neutrophil

B. Lymphocyte

C. Monocyte

D. Eosinophil

B. Lymphocyte

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

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%

C The normal adult percentage of lymphocytes in a white cell 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.

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

A There is a 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).

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

A. Segs = 70%

B. Band = 6%

C. Mono = 15%

D. Eos = 2%

C. Mono = 15%

C 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.

Which is the first stage of erythrocytic maturation in which the cytoplasm is pink due to the formation of hemoglobin?

A. Reticulocyte

B. Pronormoblast

C. Basophilic normoblast

D. Polychromatic normoblast

D. Polychromatic normoblast

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

Which of the following can shift the hemoglobin oxygen 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

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

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

A. γ4

B. α2-γ2

C. β4

D. α2-β2

C. β4

C The structure of Hgb H is β4. Hgb H disease is a severe clinical expression of α-thalassemia in which only one α-gene out of four is functioning. This is also called Hemoglobin Barts.

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

A. Low RBC count

B. High MCV

C. Low hematocrit

D. All of these options

D. All of these options

D 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 calculations of MCH and MCHC, respectively.