Complete Blood Count

Question 1

Explain how flow cytometry and Coulter principle are used to generate CBC results.

Answer 1

Flow cytometry exploits the differences in cell size, complexity, and DNA/RNA content, and counts the number of all cells except RBCs.

RBCs are counted using the coulter principle, which states that particles pulled through an orifice, concurrent with an electric current, produce a charge impedance that is proportional to the volume of the particle traversing the orifice. This allows for RBCs to be separated.

Question 2

Define RBC count

Answer 2

Number of Red Blood cells present, measured in millions per microliter or 10^12 per liter

Question 3

Define Hemoglobin (HGB)

Answer 3

In vitro measurement of the concentration of hemoglobin released by lysed RBCs into the whole blood. Measured spectrophotometrically by converting hemoglobin into cyanmethemoglobin. Units are g/dL or g/L.

Question 4

Define Hematocrit (HCT)

Answer 4

Measure of how much of a given volume of whole blood is occupied by RBCs. Can be expressed as a percentage of whole blood, or in terms of liters per liter. (Calculated by RBC * MCV)
Rule of thumb: HCT= 3* HGB

Question 5

Define Mean Cell Volume (MCV)

Answer 5

Mean size of the RBCs counted, determined from Coulter Prinicple or manually, using equation MCV=(HCT/RBC)*10

Measured in femoliters (10^-15 L)

Question 6

Define Mean Cell Hemoglobin (MCH)

Answer 6

Mean quantity of Hemoglobin in a single red cell; parallels MCV.
Calculated via equation MCH= HGB/RBC
Measured in picograms (10^-12 g)

Question 7

Define Mean Cell Hemoglobin Concentration (MCHC)

Answer 7

Average concetration of hemoglobin in a single red cell or concentration of hemoglobin in packed red cells. Calculated via equation MCHC= HGB/HCT

Measured in g/dL or g/L

Question 8

Abnormalities based on RBC

Answer 8

Anemia: Decreased due to blood loss, peripheral destruction, or insufficient erythropoiesis in the marrow.

Erythrocytosis/Polycythemia: Increased due to reactive changes (smoking, renal cell carcinoma), thalassemia, or primary marrow neoplasm (polycythemia vera)

Question 9

Abnormalities based on HGB

Answer 9

Anemia: decreased

Erythrocytosis/Polycythemia: Increased

Question 10

Abnormalities based on HCT

Answer 10

Decreased due to anemia or fluid overload

Increased due to erythcytosis/polycythemia or dehydration

Question 11

Abnormalities based on MCV

Answer 11

Decreased: Microcytosis, iron deficiency anemia, or thalassemia
Increased: Macrocytosis, megaloblastic anemia

Question 12

Abnormalities based on MCH

Answer 12

Decreased: Hypochromatic, iron deficiency anemia
Increased: Hyperchromatic, magloblastic anemia

Question 13

Abnormalities based on MCHC

Answer 13

Decreased in moderate to severe micocytic anemia

Increased in hereditary spherocytosis

Question 14

Define White Blood Cell Count (WBC)

Answer 14

Number of white blood cells in whole blood, obtained using Coulter principle.

Question 15

Neutrophil

Answer 15

Diameter 9-15 microns
Cytoplasm slightly acidophilic
Many very fine granules
2-5 nuclear segments/lobes

Question 16

Eosinophil

Answer 16

Diameter 12-17 microns
Numerous large, round red-orange granules
1-4 nuclear lobes, usually 2

Question 17

Basophil

Answer 17

Diameter 12 microns
Numerous large, round, purple-black cytoplasmic granules
Usually two nuclear lobes, often covered by granules

Question 18

Monocyte

Answer 18

Diameter 15-30 microns
Large and eccentric nucleus, round kidney/horshoe shaped or lobulated
Chromatin has a skein-like or lace appareance
Abundant cytoplasm, grayish-blue, few to many fine azurophilic granules
May have intracytoplasmic vacuoles

Question 19

Lymphocyte

Answer 19

Diameter: 7-12 microns
Mostly small, can be large if reactive
Nucleus round or slightly indented
Condensed chromatin
Usually scanty bluish cytoplasm, may contain a few azurophilic granules

Question 20

Abnormal RBC morphology

Answer 20

Decreased: RBC, HCT, MCV, MCH, MCHC
Increased RDW

e.g Iron deficiency anemia (low RBC)
Spherocytes
Bite Cells (associated with G6PD deficiency)
Schistocytes (fragments rbcs)
Target cells
Sickle cells
Basophilic stippling (evenly dispersed fin blue granules)
Howell-Jolly bodies (Single dense blue dot)
Heinze body (denatured/oxidized hemoglobin attached to the inner cell membrane)

Question 21

Abnormal WBC morphology

Answer 21

Dohle Body (pale blue inclusion at the periphery of the cytoplasm)
Toxic Granulation (Hypergranularity, increased numbers and prominence of primary granules)
Hypersegmented neutrophils (more than 5 lobes, associated with megaloblastic anemia)

Question 22

Platelet count

Answer 22

Obtained using Coulter Principle, measured in thousands/microliter or billions per liter.

Platelets are small fragments of megakaryocyte cytoplasm. Diameter 2-3 microns, average volume 7-8 fL.

Irregulare outline, light blue cytoplasm. Many small azurophilic granules.

Question 23

Platelet abnormalities

Answer 23

Thrombocytopenia: decreased platelet count
Thrombocytosis: Increased platelet count