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Clinical Pathology > Hematology Instruments & Blood Cell Measurements (2) > Flashcards

Hematology Instruments & Blood Cell Measurements (2) Flashcards

Dr. Harvey

1
Q

What are the main categories of a CBC?

A

erythrocyte parameters
leukocyte counts
platelets

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2
Q

What are the two hematology instruments - types of technology?

A

electrical impedance method
laser flow cytometry method

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3
Q

Describe the impedance method

A

blood cells are diluted in saline and flow across an aperture using electric charge

arranged in single file, and the degree of resistance tells you the volume of the cell

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4
Q

What variables does the impedance method use in hematology?

A

resistance

cell volume

the change in resistance is PROPORTIONAL to cell volume

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5
Q

Cats have the biggest ____ of any domestic animals regarding hematology

A

platelets

cannot be read using impedance method

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6
Q

What is the function of impedance instruments?

A

count and size cells

providing cell volume distributions

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7
Q

What are the limitations of impedance instruments?

A

cannot determine the intracellular contents of the cells

cannot do platelet counts accurately in cats

limited accuracy but excellent precision

cannot perform reticulocyte counts

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8
Q

What are the parts of laser flow cytometry? What do they show?

A

forward scatter - size
side scatter - complexity/granularity

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9
Q

The forward scatter measures the cell’s ____

A

shadow

a relative indicator of the cell’s size

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10
Q

List a type of cell that has high amounts of side scatter

A

neutrophils (granulocytes) - with their multilobed nucleus and granules

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11
Q

List a type of cell that has low amounts of side scatter

A

lymphocytes - have a high nucleus to cytoplasm ratio and scant cytoplasm

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12
Q

Laser flow cytometry counts and classifies cells based on ___

A

extinction of light and scattered light

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13
Q

What can laser flow cytometry count that impedance cannot?

A

reticulocytes

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14
Q

How do automated cell counters calculate hematocrit?

A

from the mean cell volume (MCV) and RBC

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15
Q

How do you determine hemoglobin?

A

spectrophotometry

using a sodium lauryl sulfate reagent

measure absorbance and protein conc.

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16
Q

What is the mean cell volume MCV?

A

average volume of a single erythrocyte, measured in femtoliters

determined directly in hematology analyzers

17
Q

What is mean cell hemoglobin, or MCH?

A

average amount of hemoglobin in a single erythrocyte (picogram = 10^-12 g)

18
Q

What does MCH generally correlate directly with?

A

mean cell volume (MCV) - because of changes in erythrocyte size

19
Q

How is MCHC (%) reported?

A

as g/dL of packed erythrocytes NOT g/dL whole blood

19
Q

What is MCHC?

A

mean cell hemoglobin concentration

20
Q

What is RDW?

A

red cell distribution width

uses standard deviation of erythrocyte volumes / MCV x 100

remember Gaussian curve and sd units

21
Q

What is the significance of RDW?

A

it is an electronic measure of anisocytosis

22
Q

What is spuriously increased RDW?

A

erythrocyte agglutination

platelets counted in erythrocyte histogram of severely anemic patients

23
Q

Only ________ reticulocytes are counted in most instruments

A

aggregate

24
Q

What are spurious reticulocytosis?

A

Howell-jolly bodies
large immature bodies or platelet clumps
autofluorescence

25
Q

Platelet aggregates can result in _____

A

false thrombocytopenia (low platelets), especially in cats

26
Q

What is MPV?

A

mean platelet volume

27
Q

What is an error in blood cell measurements regarding erythrocytes? How do you correct it?

A

nucleated erythrocytes in blood - counted as leukocytes by manual and most automated cell counters

calculate corrected total leukocyte count before calculating absolute differential leukocyte counts

28
Q

What are some sample errors in blood cell measurements?

A

not going to be asked specifically on exam I dont think

also hemolysis, lipemia, Heinz bodies

Clinical Pathology (28 decks)

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