Introduction to haematology

Question 1

What tube is usually used for haematology?

Answer 1

EDTA

Question 2

When is a citrate tube better for haematology?

Answer 2

Assessing feline platelet counts - clump less readily

Question 3

When would you use heparised blood for haematology?

Answer 3

Species in which only small samples can be taken (exotics) as can be used for biochem as well

Question 4

How thick is the buffy coat usually after centrifuge?

Answer 4

1-2mm

Question 5

What can a thicker buffy coat layer indicate?

Answer 5

High white cell counts: inflammation or leukaemia

Question 6

What can cause plasma haemolysis?

Answer 6

In vitro haemolysis (prolonged storage time, vigourous mixing, small needle used)

In vivo haemolysis (haemolytic anaemia

Question 7

Plasma protein reference range

Answer 7

2-3g/L

Question 8

Causes of low PCV and low plasma protein

Answer 8

Recent (>4hrs) or ongoing external haemorrhage

Internal haemorrhage may only cause a mild reduction in plasma proteins and then they are rapidly reabsorbed

Question 9

Causes of low PCV and normal or high plasma protein

Answer 9

Anaemia due to haemolysis or reduced red cell production

Question 10

Causes of normal PCV with low plasma protein

Answer 10

Usually due to hypoalbuminaemia caused by decreased production (liver disease, small intestinal malabsorption) or increased albumin loss (intestinal loss, losses in urine)

Question 11

Causes of normal PCV and high plasma protein

Answer 11

Usually due to hyperglobulinaemia - seen with myeloma and some B cell lymphomas, as well as some infectious diseases

Question 12

Causes of high PCV with low/normal plasma protein

Answer 12

Could indicate increased numbers of red blood cells (polycythaemia) - uncommon

More likely to be due to dehydration with another disorder causing decreased plasma protein

Question 13

Causes of high PCV and high plasma protein

Answer 13

Seen with dehydration - water lost from body results in increased concentration of both red cells and protein.

Question 14

Basic overview of blood smear examination

Answer 14

Following staining start on low power and scan feathered edge to look for platelet clumps, large cells, and parasites

Move into the monolayer, where approx. 50% of cells are touching

Go to high power -100x, and count platelets seen over 5 fields (should be at least 15 per hpf), multiply by 15 to get approx count in x10^9/L

Look for evidence of variation in platelet size and presence of macropaltelets (normal in CKCS)

Look at erythrocytes: colour (central pallor. polychromasia, hypochromasia etc.), metarubricytes (nucleated)

Finally look at leukocytes (middle and edge of smear) count no of neutrophils, lymphocytes, eosinophils, and monocytes in 100 consecutive cells

Evaluate neutrophils for evidence of left shift and toxic changes

Evaluate size of lymphocytes

Question 15

Evidence of left shift

Answer 15

Band neutrophils

Question 16

Toxic changes in neutrophils

Answer 16

Dohle bodies
Basophilic and/or formy or vacuolated cytoplasm