7. RBC Indices

Question 1

What is a complete blood count?

Answer 1

gives us the minimum set of values that are reliable and cost effective
tests included in a CBC can be done with automated machines or manually

Question 2

What tests does a CBC include? What do these tests make up? What do the total WBC count and differential count make up?

Answer 2

Includes: total red blood cell cound, PCV/hematocrit, plasma protein concentration (total protein -TP), total WBC, hemoglobin (Hg/Hgb) concentration, erythrocyte indices
Blood film eval: differential count, morphology of WBC and RBC, platelet examination
^^ These tests make up Hemogram
The total WBC count and diff. count make up the leukogram

Question 3

What is a packed cell volume (PCV)

Answer 3

% of whole blood made up of erythrocytes (RBC’s). used to eval hydration status of patient, used to diagnose anemia or erythrocytosis
This test can be run as a single test or as part of the CBC
This test is extremely accurate with an inherent error of +/- 1%
Hematocrit (Hct) or microhematocrit (mHct) is the PCV expressed as a volume
Ex. PCV = 42%, Hct = 0.42L/L

Question 4

What do you need to run a PCV? What are some common errors that could occur?

Answer 4

A microhematocrit tubes, sealant, reader card, and a microhematocrit centrifuge (each clinic required by SVMA to have these)
Errors from: failure to mix blood sample properly, hemolysis of sample, insufficient centrifuge time &/or speed which leads to incomplete packing of cells

Question 5

What are the steps to running a PCV procedure?

Answer 5

1. mix blood gently
2. Fill 2 microhematocrit tubes about 75% full using capillary action
3. Hold tube horizontally until placed into sealant, one end is inserted into sealant at least 2x
4. Load centrifube, make sure sealant end is towards the outer edge of the centrifube
5. Follow the centrifuge instructions - usually 2-5 minutes on the hematocrit setting
6. once sample done spinning, read

Question 6

What do we look for when reading the PCV?

Answer 6

The plasma layer for color and clarity
THe buffy coat for width and color
the PCV for width

Question 7

What might yellow plasma indicate when reading PCV?

Answer 7

May be due to liver dz, hemolytic disorders, nutritional supplements, dehydration
Can be normal in plant and grain eaters (ruminants and poultry) due to carotenoids in the feed

Question 8

What might pink plasma indicate when reading pCV?

Answer 8

evidence of hemolysis, usually due to poor collection of handling methods, may be due to intravascular disorders, will affect other test results

Question 9

What does white plasma indicate when reading PCV?

Answer 9

lipemia is due to the presence of fat in blood
seen after eating, rarely pathologic, interferes w/ many chemical tests

Question 10

What does the middle layer when reading PCV indicate

Answer 10

buffy coat, contains the WBC’s and platelets, white appearance
Will appear red when there are significant #’s of nucleated RBC’s present

Question 11

How thick should a buffy coat be?

Answer 11

~1mm or the thickness of a dime

Question 12

How is PCV measured?

Answer 12

measured at the intersection of the top of the RBC mass and the buffy coat, measured on a reader card
Results are in % and then converted to 0.XX L/L

Question 13

What is the significance of PCV results?

Answer 13

used as a screening tests for pathological conditions
lower than normal values indicate anemia (can be falsely dec if not enough blood was added to the tube or diluted by anticoagulant)
higher than normal values indicate polycythemia or dehydration - dehydration is more common
Make sure to mix your sample well immediately b4 filling the microhematocrit tubes

Question 14

What are the normal PCV values for common species like canine and feline?

Answer 14

K9 - 37-55
Fel - 30-45

Question 15

What are the normal PCV values for common species like equine and bovine

Answer 15

Eq: 32-57
Bov: 24-42

Question 16

What are the normal PCV values for common species like ovine, caprine and porcine

Answer 16

ovine: 25-45
Caprine: 21-38
Porcine: 32-43

Question 17

How do we assess plasam protein concentration

Answer 17

this test will give an estimate of total protein concentration of the same sample
it require a refractometer and two spun microhematocrit tubes
after the PCV has been read, break tube carefully break it above buffy coat. A few drops on the plasma are placed on the prism of the refractometer
let plasma flow onto the refractometer, DO NOT tap on the crystal

Question 18

What are the unit for plasma protein concentration

Answer 18

close lid gently and look @ TP scale (it will be in g/100ml, on older refractometers it will be labelled as g/dL)
g/dL = g/100ml, must be converted to g/L with NO decimal place

Question 19

What is hemoglobin

Answer 19

hemoglobin is the function unit of the RBC - it carries oxygen to the tissues and CO2 to the lungs to be expired
Hemoglobin is made up of heme portion containing iron (Fe) and the globin portion made up of paired AA chains

Question 20

How are hemoglobins measured?

Answer 20

measure the quantity of hemoglobin per unit of blood volume
1. Automated analyzers - some estimate hemoglobin content based on RBC count, gives values for all forms of hemoglobin uses a lysing agent, some dedicated hemoglobin analyzers only test for oxyhemoglobin and a very accurate when properly maintained
2. calculated from PCV
PCV divide by 3 = hemoglobin in g/100mL, convert g/L with no decimal places or exponents

Question 21

How do we calculate hemoglobin? What is it reported in?

Answer 21

PCV / 3 = Hgb in g/100mL, then convert to g/L w/ no decimal places or exponents
EX: PCV = 43%
43 / 3 = 14g/100mL x 1000ml/L = 140g/L

Question 22

What should be done if 120g/L in dogs or 80 g/L in cats is recorded?

Answer 22

A reticulocyte stain should be evaluated

Question 23

What are the normal hgb values for equine, bovine, k9 and feel?

Answer 23

Equine: 110-180g/L
Bovine: 80-140g/L
Canine: 120-200g/L
Feline: 110-160g/L

Question 24

What are erythrocyte indices

Answer 24

AKA mean corpuscular values
helpful for classification of some types of anemia
Includes
Mean corpuscular volume
Mean corpuscular hemoglobin
Mean corpusclar hemoglobin concentration

Question 25

How are erythrocyte indices calculated? What tests must be performed to calculate erythrocyte indices manually?

Answer 25

Calculated by automated machines
manually done through a PCV, Hgb, and total RBC count
Values obtained should always be compared to morphological features on the cells of the differential smear

Question 26

What is mean corpuscular volume? How do we calculate it and what do we record it as?

Answer 26

Deterimes average size of individual RBC’s
(PVC / RBC count) x 10 = MCV in fL
Ex. (42% /6.0) x 10 = 70fl
Record as whole number

Question 27

What is mean corpuscular hemoglobin? What is it recorded as?

Answer 27

hgb gives RBC’s their color and determines mean weight of the hgb in the average RBC. Measured in picograms and recorded with 1 decimal place
Hgb / RBC count
EX: 150g/L / 5.0 = 30.0

Question 28

What is mean corpuscular hemoglobin concentration? What do you report it as?

Answer 28

Determines the conc of Hgb in the average RBC. ratio of weight of hgb to the volume in which it is contained, expressed as g/L
report as whole #
Normal range is 300-360g/L
(Hgb g/L / PCV) x 100 = MCHC g/L
EX: (140 / 42) x 100 = 333g/L