1. Complete Blood Count and Anemia
Clinical Pathology

2. Blood Composition Separates into three components:
Red Blood Cells (RBC’s)
White Blood Cells and platelets (buffy coat)
Plasma
Bottom 1/3 to ½ of tube contains the heaviest of cellular material (the RBC’s).

3. Hematocrit=PCV (Packed Cell Volume)
To determine hematocrit, whole blood is centrifuged to pellet the red blood cells.
Plasma remains on the top of the red cells.
The fraction of blood that is packed is the hematocrit and is read as a percentage.

4. Complete Blood Count
Provides a minimum set of values and is cost effective.
Can be done manually or with automated systems.
CBC should contain:
Packed Cell Volume (PCV or Hct)
Plasma Protein Concentration
Total White Blood Cell count
Blood smear with morphology
WBC differential count
Reticulocyte count

5. Manual Procedures
PCV- whole blood is collected in anticoagulant, placed in capillary tube, sealed, centrifuged and read.
Total protein- plasma is read with a refractometer.

6. More Manual Procedures
Absolute WBC: Total number of white blood cells in the blood.
Unopette hematocytometer test kits are used to lyses RBC’s and to make a 1:100 dilution.
WBC’s are counted within the grid and calculated to reflect the WBC in the blood.

7. Manual Procedures Continued
Differential Leukocyte Count: a relative count is performed by counting and classifying at least 100 leukoctyes.
This gives a percentage of each cell type which is then used to calculate the absolute numbers of each cell type.
May use a counter in order to perform this count.

8. Instrumentation
Electronic cell counters: based on the principle that cells are poor electrical conductors.
Measured volume of diluted blood is drawn between two electrodes, causing a resistance in the electrical current.
QBC: Quantitative Buffy Coat System
Utilizes differential centrifugation and quantification of cellular elements in a specialized microhematocrit tube.

10. Red Blood Cell Indices PCV (hematocrit) Hemoglobin Concentration
Total red blood cell count
These are used to classify the type of anemia.

11. Anemia
Literally means “no blood” but clinically means low total blood hemoglobin.
Absolute anemia: most common, caused by failure to produce adequate numbers of cells or by a loss of cells at a rate greater than can be produced.

12. Clinical Signs of Anemia
Pale mucous membranes
Exercise intolerance
Tachycardia
Panting
Icterus if anemia is caused by RBC breakdown in bloodstream.

13. Classification of Anemia
By RBC size (MCV):
Macrocytic
Erythrocytes are larger than normal.
Usually in the presence of regenerative anemia.
May be seen in FeLv
May see anisocytosis
Normocytic
Microcytic
Cells are smaller than normal which has been determined by Mean Cell Volume (MCV).
Usually occurs with iron deficiency caused by chronic blood loss or parasitism
By Hemoglobin concentration (MCHC)
Hypochromatic
RBC’s have decreased density of the characteristic hemoglobin color.
Frequently observed in iron deficiency caused by chronic blood loss or parasitism.
Normochromatic

14. MCV
Describes cells as normocytic, microcytic, or macrocytic. Calculates the average volume of rbc’s.
MCV=(Hematocrit x 10)/RBC count in millions
Ex:
Canine patient with hematocrit of 42% and RBC count of 6 million/ul.
Normal: 66-77

15. MCV causes of Increases
Reticulocytosis
Congenital issues (poodles)
Cats with FeLv
RBC agglutination
B12 deficiency (rare)

16. MCV causes of decreases
Abnormal Hgb synthesis (iron deficiency from chronic blood loss is the most common).
Immature animals
Dogs with PSS.
Congenital (Akitas)

17. MCHC
Mean Corpuscular Hemaglobin Concentration describes cells as normochromatic or hypochromatic.
MCHC= (Hgb)/(Hct) x 100
Ex.
Same patient as before with Hgb content of 14 g/dL
Normal: 31-36%

18. MCHC causes if high Intravascular hemolysis
Inaccurate Hgb reading (Heinz bodies, lipemia, etc).
Machine error
True hyperchromasia does not exist.

19. MCHC causes if low
Small reticulocytes
Iron deficiency.

20. Classification According to Bone Marrow Response
Regenerative anemia:
Characterized by evidence of increased production and delivery of new erythrocytes into circulation.
Usually suggests an extra bone marrow cause (blood loss, hemolysis, etc.).,
Diagnosis:
Peripheral blood smear.
Will see macrocytosis, polychromasia with Wright’s stain, reticulocytosis with methylene blue stain, may also see increased numbers of nucleated RBC’s

21. Nonregenerative anemia:
Indicates anemia is result of bone marrow defect.
No response evident in peripheral blood.
Marrow examination may be helpful with the diagnosis.

22. Reticulocyte Count
Probably the most important diagnostic tool used in the evaluation of anemia.
Expressed as a % of the RBC’s present.
Corrected to take in account the reduced number of circulating RBC’s in the anemic animal.
Called CRC or Corrected Reticulocyte Count
The lifespan of a normal RBC is about 100 days.
Bone marrow should replace 1 % of the RBC’s daily so the reticulocyte count should be %.

23. Reticulocyte count continued
Expressed as # of retics/100 RBC’s
Some species variation in reticulocyte response exists.
Normal horse and cattle blood do not have reticulocytes.
CRC= (patient Hct)/(Normal Hct) x reticulocyte count

24. Example
Dog with an observed reticulocyte count of 9 % and Hct of 25%. Normal Hct is 45.
Interpretation A (expressed in %):
Normal
Less than or equal to 1 in dog
Less than or equal to 0.4 in cat
Mild
Dog: 1-4
Cat: 0.5-2
Moderate
Dog: 5-10
Cat: 2-3
Marked
Dog: greater than 10
Cat: 3-4

25. Blood Loss Anemia
Results from excessive hemorrhage although source can be subtle.
Must determine if blood loss is internal or external.
Possible causes:
Trauma
Persistent bleeding lesions
Thrombocytopenia
Coagulopathies
Heavy parasitism
Iatrogenic causes

26. Acute Blood Loss Anemia due to loss of blood in a sudden episode.
All RBC parameters are normal for the first 12 hours.
Hypovolemic shock can be apparent prior to a decreased PCV.
Anemia will be normocytic, normochromatic, and apparently unresponsive with a low CRC.
By day 4-5, the retic count increases and the anemia appears responsive.

27. Chronic Blood Loss
Blood is lost slowly and continuously for a period of time.
Body compensates for anemia by lowering oxygen-hemoglobin affinity, preferential shunting of blood to vital organs, increased cardiac output (tachycardia), and increased levels of erythropoietin.
Anemia remains unresponsive unless iron stores are depleted.
With decreasing iron stores, erythropoiesis is limited and RBC’s become smaller and deficient in Hgb (microcytic and hypochromic).
Clinical signs include lethargy, weakness, decrease exercise tolerance, anorexia, pallor, lack of grooming, mild systolic murmur.

28. Diagnostic Tests Hemogram: may see increased WBC and platelets.
Total protein: decreased
Coagulation testing: platelet count, PT, PTT, ACT.
Fecal Float: Hookworms, Whipworms
Fluids analysis from body cavities

29. Hemolytic Anemias
Result of increased erythrocyte destruction within the body.
Intravascular hemolysis: desctruction of erythrocyctes within the blood vessels and loss of Hgb from the cells.
Extravascular hemolysis: RBC’s are lysed following phagocytosis.

30. Differentials
Immune-mediated disease: AIHA, drug induced, neonatal isoerythrolysis.
Parasitic: Ehrlychiosis, Babesiosis, Hemobartonellosis, Anaplasmosis.
Toxic: Heinz body anemias, snake venom, bacterial toxins.
Infectious: EIA, Leptospirosis, Clostridia
Fragmentation: Splenic torsion, Splenic neoplasia, DIC