UNIT 1 - Lecture 2: Evaluating Erythrocytes Flashcards

1
Q

What does a hemocytometer do and when is it helpful?

A

Provides manual cell count for blood;

Helpful for low cellularity cytology (i.e. CSF) - <1000 cells/µL

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2
Q

For what spp is a hemocytometer necessary?

A

Spp with nRBCs (birds, reptiles, fish)

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3
Q

What is the impedance method?

A

Uses changes in electrical resistance to count cells and can provide an assessment of cell volume

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4
Q

What are the 3 steps to the impedance method?

A
  1. Constant electrical current applied across an aperture
  2. Cells suspended in saline move through the aperture “single file”
  3. Cells pass through aperture –> impedance altered –> voltage pulse generated (# pulses = cell #, amplitude = cell volume)
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5
Q

What are the 2 steps to flow cytometry?

A
  1. Cells pass through laser in “single file”
  2. Light scatters at different angles, which is detected by instrument (–> cell #, volume, complexity)
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6
Q

What 4 things does a CBC do?

A
  1. Assesses total RBC mass in peripheral blood (Hct/PCV, [RCB], [Hgb])
  2. Describes the RBC population (MCV, MCH, MCHC, RDW)
  3. Assesses regeneration (retic%, retic absolute)
  4. Evaluates RBC morphological changes (blood smear)
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7
Q

What is [RBC] and what is it used for?

A

RBCs / unit volume of blood

Used to calculate MCH, +/- MCV

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8
Q

What is PCV AKA?

A

spun hematocrit

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9
Q

What is PCV?

A

Packed cell volume;

% of blood comprised of RBCs

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10
Q

What does a low PCV mean? High?

A

Low = anemia

High = erythrocytosis

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11
Q

What is normal plasma color for cats/dogs? Horses/cattle?

A

Cats/dogs = colorless

Horses/cattle = light yellow

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12
Q

What does icteric plasma look like? Hemolytic? Lipemic?

A

Icteric = clear and bright yellow

Hemolytic = clear and pink to red (bc of free Hgb)

Lipemic = white and cloudy

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13
Q

What is Hct?

A

Hematocrit - calculated value, essentially the same as PCV

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14
Q

In animals with biconcave RBCs, the Hgb is ____ of the Hct.

A

~1/3

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15
Q

What are the 2 methods of measurement of Hgb? Which is more accurate?

A
  1. Direct spectrophotometric
  2. Optical measurement using laser light scatter (more accurate)
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16
Q

Direct spectophotometry to measure Hgb assumes that _____.

A

All Hgb is within cells

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17
Q

Optical measurement to measure Hgb measures ______.

A

Hgb content in RBCs directly

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18
Q

What things can interfere with measured [Hgb]?

A

Lipemia, Heinz bodies, oxyglobin (can falsely increase Hgb)

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19
Q

What condition is occurring when RBC count, PCV/Hct, and Hgb are low?

A

anemia

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20
Q

What condition is occurring when RBC count, PCV/Hct, and Hgb are high?

A

erythrocytosis

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21
Q

What is MCV?

A

Mean Corpuscular Volume;

Volume per avg RBC

22
Q

What is a decreased MCV called? WRI? Increased?

A

Decreased = microcytic

WRI = normocytic

Increased = macrocytic

23
Q

What are artifactual causes for a decreased MCV?

A
  1. Excess EDTA - cellular dehydration
  2. Hyponatremia –> decreased RBC osmolality –> exposure to isotonic diluent in instrument –> in vitro osmosis –> cell shrinkage
24
Q

What are physiologic causes for a decreased MCV?

A
  1. Puppies and kittens <8 to 16 weeks old
  2. Calves and foals <1 year old
  3. Breed associations: Akita, Shiba Inu, Sharpei, Chow, Abyssinian
25
Q

What are pathophysiologic causes for a decreased MCV?

A
  1. Iron deficiency (limited Hgb sythesis)
  2. Liver dz (PSS)
26
Q

What are artifactual causes for an increased MCV?

A
  1. Agglutination/microagglutination
  2. Prolonged storage
  3. Hyperosmolality (hypernatremia)
27
Q

What are physiologic causes for an increased MCV?

A

Breeds: mini and toy Poodles & polled Herefords

28
Q

What is a pathological cause for an increased MCV?

A

regenerative anemia

29
Q

What 3 things can cause abnormal DNA synthesis/increased MCV?

A
  1. Myelodysplastic syndrome (cancer)
  2. Folate (B12) deficiency
  3. Cobalt deficiency
30
Q

What can cause an increased MCV in cats?

A

hyperthyroidism

31
Q

What is MCH?

A

Mean Cell Hgb;

No added value/not as meaningful as MCHC;

Correlates with MCV directly except in regeneration

32
Q

What is MCHC?

A

Mean Cell Hgb Concentration;

Avg [Hgb] per RBC;

Preferred over MCH, more accurate, considers RBC size

33
Q

What is decreased MCHC called?

A

hypochromic

34
Q

What is MCHC that is WRI called?

A

normochromic

35
Q

What artifact can cause hypochromasia?

A

RBC swelling with storage or hyperosmolality

36
Q

What are pathophysiological causes for hypochromasia?

A
  1. Regenerative anemia
  2. Iron deficiency
  3. PSS
37
Q

What does an increased MCHC mean?

A

Hemolysis (free, extracellular Hgb)

Oxyglobin (detected by spectrophotometer and mischaracterized as Hgb)

Lipemia (detected by spectrophotometer and mischaracterized as Hgb)

Heinz bodies (Hgb measured but HB do not contribute to RBC # detected by the instrument)

38
Q

What is RDW?

A

Red Cell Distribution Width;

Coefficient of variation of RBC size (volume)

39
Q

What does RDW correlate with?

A

Anisocytosis on blood smear

40
Q

What does increased RDW mean?

A

Indicates anisocytosis

41
Q

What are potential causes for an increased RDW?

A

Regenerative anemia

Microcytes and/or macrocytes present

42
Q

What is a reticulocyte?

A

Anucleated, immature RBC larger than a mature RBC

43
Q

NMB stains Heinz bodies and retic RNA dark blue = _____

A

reticulocyte

44
Q

Wright-type stain stains RBC blue due to residual RNA = _____

A

polychromatophil

45
Q

Reticulocytosis or increased polychromasia are important indicators of accelerated _____ or “_____.”

A

erythropoiesis, regeneration

46
Q

What are the 2 types of retics in cats?

A

Aggregate and punctate

47
Q

What are aggregate retics?

A

Correspond to polychromatophils on blood smear stained with Wright’s type stain;

Counted by automated instrument

48
Q

What is a punctate retic?

A

Persists in circulation for several weeks –> not a good indicator of a current regenerative response

49
Q

In what spp can we NOT use retic count to assess regen response?

A

horses

50
Q

What is necessary to characterize a regen response in horses?

A

Serial CBCs or bone marrow aspirate/biopsy

51
Q

What 3 things can be used to assess reticulocytosis and which do/do not account for anemia?

A
  1. Retic % (RP) - does not account for deg of anemia
  2. Corrected RP (CRP)
  3. Retic [] - preferred method for eval marrow response to anemia
52
Q

If corrected retic % is ____ than reference interval = regeneration

A

greater