Haematology 1

Question 1

List the different components of a full haemogram

Answer 1

It tests mainly the three components of the blood namely Red Blood Cells, White Blood Cells and Platelets, comparing with normal range or reference interval for the species.

Question 2

What are haematological abnormalities a sign of?

Answer 2

Underlying disease, often life threatening consequences

Question 3

What are clinical signs that suggest haematological abnormalities will be detected?

Answer 3

• Pallor, exercise tolerance
• Bleeding (bleeding from wound, GI tract – dark faces)
• Pyrexia (raised body temp, expect inflammatory condition

Question 4

Where is blood taken from and what test tube put into?

Answer 4

1. taken from superficial vein

2. into anticoagulant EDTA (best to preserve morphology as well as prevent clotting)

Question 5

Caution when interpreting lab results

Answer 5

If not supported by clinical signs then the abnormality may be due to error, artifact or biological variability (breed differences)

Question 6

When sampling need:

Answer 6

1. Adequate animal restrain - cats more restrain the less cooperative
2. big palpable vein if possible - sample quicker, less opportunity for it to clot
3. Be quick, avoid animal struggling- platelet clumps and blood clots may form if sampling takes too long

Question 7

Sampling processing avoid:

Answer 7

1. Inadequate mixing of specimen
2. Haemolysed specimens (break down) (in vitro)
3. Lipaemic (fatty) specimens (fasting)
4. Clotted specimens – useless, need to take another sample. If send this to lab, have to call in patient again 1 day or so later!
5. Platelet clumps (microscopy) -
6. Diluted specimens – more problem with reptiles, dilution with lymph
7. These are all possible sources of pre-analytical error!
8. don’t shake
9. look at all times to identify clotting

Question 8

What calculations are routinely made on erythrocyte data?

Answer 8

1. Mean corpuscular volume, MCV
2. Mean corpuscular haemoglobin concentration, MCHC
3. Mean corpuscular haemoglobin, MCH

Question 9

How to work MCV, MCHC and MCH

Answer 9

1. Mean corpuscular volume - ratio PCV/RBC. This gives the average size of the patient’s red cell in fL.
2. Mean corpuscular haemoglobin - Concentration [Hb]/PVC. This gives the proportion of red cell mass that is attributed to Hb (mg/dL).
3. Mean corpuscular haemoglobin - ratio Hb/RBC. This gives the average amount of Hb per red cell in pg.

Question 10

What does it mean if Hb, PCV or RBC count are below or above reported reference interval for that species?

Answer 10

Anaemia or erythrocytosis

Question 11

What dogs have blood cell abnormalities?

Answer 11

Greyhounds typically have higher Hb, Hct/PCV (same thing!) and RBC count.
Pups typically have much lower PCV than normal dog

Question 12

Uses of RBC measurements:

Answer 12

1. RBC count, Hb, PCV determine O2 carrying capacity of blood is adequate
2. H2O has been lost from the circulation [dehydration]
3. Anaemic - loss of blood oxygen carrying caoacity- present if any of the Red cell mass measurement (RBC count, PCV, Hb) below reference interval
   - –
4. MCV - estimate of red cell size (corpuscular volume)

Question 13

In anaemia how does MCV vary?

Answer 13

in 3 possible ways

1. Raised
2. Normal MCV -
3. Reduced MCV

Question 14

Talk in detail about anaemia MCV varying

Answer 14

1. Raised MCV - - erythropoiesis is increased e.g. respond to an increased RBC loss = higher proportion of young RBC (larger), increasing average RBC size. Indicates anaemia with high MCV usually indicates regenerative anaemia
2. Normal MCV - may be non-regenerative (no increase in release of juvenile RBC) but also regenerative (if numbers are not high enough to shift the whole population – remember it is an average
3. Reduced MCV - usually indicates a type of anaemia in which smaller erythrocytes are produced. This is typical of iron deficiency (remember: erythroid precursors keep dividing until they reach the critical Hb concentration

Question 15

when does Mean corpuscular haemoglobin concentration, MCHC, decrease

Answer 15

1. when more juvenile RBCs are present (they are larger then mature RBCs and have not stopped producing Hb yet so their Hb concentration is lower then in mature) OR
2. in iron deficiency anaemia

Question 16

Where does anaemia arise from

Answer 16

acute or chronic haemorrhage – proportional loss of all blood components (plasma and cells

Question 17

Initial result of anaemia

Answer 17

decrease BV whilst proportion between plasma and cells is maintained so Hct &TP unchanged

Question 18

Prolonged anaemia

Answer 18

activation mechanisms to maintain volaemia - influx H20 from Extra cellular space = dilution = reduction of Hct and TP

Question 19

Acute blood loss

Answer 19

1. Bone marrow able to compensate
2. It increases erythropoiesis and red cell mass (Hct, RBC, Hb) normalises 1-2 weeks if blood loss stopped
3. Decreases TP expected
4. Evidence of regeneration- inc juvenile RBC (reticulocytes) if healthy bone marrow
5. Lag of 2-3 days before seeing inc young RBC circulation

Question 20

Chronic blood loss anaemia

Answer 20

1. May lead to depletion of iron stores – Fe deficiency
2. Iron stores are sbundant in adults so it takes less than 1 month of continued bleeding for IDA to develop
3. May be regenerative or non regenerative: eventually depletion of iron will slow down erythropoiesis (irone is essential)

Question 21

Causes of anaemia

Answer 21

1. Trauma
2. bleeding lesions
3. blood sucking parasites
4. Bloot clotting abnormalities
5. Reduced blood production from bone marrow

Question 22

what is haemolysis

Answer 22

RBC destruction

It can be immune mediated or non immune mediated

Question 23

Immune mediated haemolytic anaemia

Answer 23

Most common cause of haemolysis in cats and dogs

1. The production of antibodies against patients RBC - removal by macrophages
2. Complement may also be involved

Question 24

Non immune mediated anaemia causes

Answer 24

1. Oxidative damage ‘poisons’ (onion, garlic, red maple in horses, some drugs such as paracetamol in cats, zinc, copper in sheep, forage brassicas, and others)
2. intra-erythrocytic parasites (Babesia)
3. bacteria (Leptospira, Clostridium)
4. viruses (Equine Infectious Anaemia)
5. mechanical damage (altered vasculature - angiopathic anaemia)
6. osmotic shock
7. erythrocyte enzymatic defects

Question 25

Classification of anaemia based on haemogram

Answer 25

1. Degree of severity
2. Regenerative Response (polychromasia/ retics count) - regen Vs non
3. Erythrocyte indexes (MCV, MCHC) - microcytic/ normocytic/ macrocytic AND Hypochromic/ normochromic

Question 26

Why classify anaemia?

Answer 26

1. to identify underlying pathophysiologic mechanism: bloos loss? Haemolysis? Defective prodiction by BM? degenerative or non?
   Clinical signs

Question 27

What is the difference between regenerative and non regenerative anaemia?

Answer 27

Regenerative - decreased O2 carrying capacity - inc RBC production by bone marrow - release higher numbers juvenile RBC in circulation.
blood loss and haemolysis
NONregenerative - Bone marrow fails to respond to decreased O2 carrying capacity = primary BM disease, lack of erythropoietin production (chronic kidney disease), Alteration of microenvironment

Question 28

How to identify juvenille RBC

Answer 28

Pink stain - larger and bluer RBC

Blue stain - still contain rough ER with ribosomes and RNA

Question 29

NAme of raised red cell count

Answer 29

(erythrocytosis or called polycytaemia

Question 30

When is raised RBC count seen in dogs and cattle ususally

Answer 30

dehydration (relative erythrocytosis  due to decrease of water component of blood). Rarely absolute (due to true increase in RBC mass) may be due to abnormal production of EPO or neoplastic (independent from EPO.