Evaluating RBC

Question 1

Red Blood cell concentration

Answer 1

of RBCs per unit volume of blood. This is referred to as the RBC count.

Question 2

Packed cell volume

Answer 2

Volume (%) of blood comprised of RBC’s.

Question 3

What does an increased PCV indicate

Answer 3

erythrocytosis

Question 4

What does a decreased PCV indicate

Answer 4

anemia, over hydration

Question 5

Hematocrit

Answer 5

Volume % of blood comprised of RBC’s

This is not equal to PCV, as it is a calculated value. Generally they are close to one another

Question 6

What is the relationship between hematocrit and hemoglobin

Answer 6

Hemoglobin is 1/3 of the hematocrit

Question 7

What interferences can be measure hemoglobin? ie. falsely increase the measure of hemoglobin

Answer 7

Heinz bodies, Lipemia, oxyglobin

Question 8

erythrocytosis

Answer 8

high RBC count

• This can be caused by breed differences (sighthounds)
• Dehydration or splenic contraction
• Primary and secondary absolute erythrocytosis

Question 9

Anemia

Answer 9

Low RBC count

Can be seen as decreased RBC count, PCV/Hct, Hemoglobin

Question 10

MCV

Answer 10

Mean Corpuscular Volume
This is the volume per average RBC
- this value historically has been calculated

Question 11

Decreased MCV is termed:

Answer 11

Microcytic

Question 12

MCV within the Reference interval is termed:

Answer 12

Normocytic

Question 13

Increased MCV is termed:

Answer 13

Macrocytic

Question 14

Cause of MCV below reference interval

Answer 14

Physiologic cause
- Puppies and kittens < 16 w old, calves and foals <1 year
- Breed associations
Pathophysiological cause
- Iron deficiency
- Often seen with concurrent hypochromasia (Low MCHC)
- Fe- deficiency limits Hgb synthesis. Sufficient Hgb provides negative feedback to stop additional RBC division. therefore, Fe-deficient cells undergo additional divisions than normal resulting in a smaller cell
- Liver disease- portosystemic shunt

Question 15

Artifactual Causes of MCV- above reference interval

Answer 15

(Macrocytic condition)
Artifactual Causes:
- Agglutination/microagglutination (analizers will read agglutinated RBC’s as a single large cell (high MCV and low MCHC)
- Prolonged storrage causing cellular swelling (decreases MCHC)
- Hyperosmolality- persistent hyperosmolar environment -> increased RBC osmolality -> exposure to isotonic diluent in instrument causes in vitro osmosis -> cell swelling

Question 16

Causes of MCV above reference interval (macrocytic condition)

Answer 16

Physiologic 
- Breeds: minature and toy poodles and polled Herefords
Pathological 
- ** Regenerative anemia
Abnormal DNA synthesis
- myelodysplastic syndrome (cancer) 
- folate deficiency
- cobalt deficiency 
Other: hyperthyroidism in cats

Question 17

What is MCH

Answer 17

Mean Cell hemoglobin Concentration

• This is the amount of hemoglobin per average RBC. this is not as meaningful as MCHC
• no added value since it depends on MCV and MCHC

Question 18

What is MCHC

Answer 18

Mean Cell Hemoglobin Concentration

This is the average hemoglobin per average erythrocyte.

• this is more acurate because it considers the size of the RBC as well.
• calculated value

Question 19

What is the term for a low MCHC:

Answer 19

hypochromic

Question 20

What is the term for a normal MCHC:

Answer 20

normochromic

Question 21

What are the causes for a hypochromic state?

Answer 21

Artifact- RBC swelling with storage or hyperosmolality
Pathophysiological
- Regenerative anemia- immature RBC have less hemoglobin than mature RBC’s
- Iron deficiency- animals often anemic by time there is hypochromasia detected (low MCHC without anemia should NOT be automatically assumed to be iron defficiency)
- Portosystemic shunts
-Attributed to relative or functional iron deficiency ( iton sequestered, but not deficienct)
- Decreased hemoglobin production (uncommon, but lead poisoning, B6 deficiency, copper deficiency)

Question 22

Why does hypochromasia not really happen?

Answer 22

RBC’s will never pack more hemoglobin than needed into itself.

Question 23

What does an elevated MCHC mean?

Answer 23

• Hemolysis- there is free, extracellular hemoglobin
• Oxyglobin- will be detected by spectrophotometer and mischaracterizedas hemoglobin (blood replacement Product)
• Lipemia- will be detected by spectrophotometer and mischaracterized as Hgb
• Heinz bodies- Hemoglobin measured, but Heinz bodies do not contribute to RBC number detected by the instrument

Question 24

RDW stands for what?

Answer 24

Red Cell Distribution Width - this is a coefficient of variation of RBC size.
This correlates with anisocytosis (variable RBC changes on Blood smear evaluation)

Question 25

Increased RDW indicates what?

Answer 25

anisocytosis Caused by: - regenerative anemia Microcytes present or macrocytes present