Haematology 1 Flashcards
List the different components of a full haemogram
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.
What are haematological abnormalities a sign of?
Underlying disease, often life threatening consequences
What are clinical signs that suggest haematological abnormalities will be detected?
- Pallor, exercise tolerance
- Bleeding (bleeding from wound, GI tract – dark faces)
- Pyrexia (raised body temp, expect inflammatory condition
Where is blood taken from and what test tube put into?
- taken from superficial vein
2. into anticoagulant EDTA (best to preserve morphology as well as prevent clotting)
Caution when interpreting lab results
If not supported by clinical signs then the abnormality may be due to error, artifact or biological variability (breed differences)
When sampling need:
- Adequate animal restrain - cats more restrain the less cooperative
- big palpable vein if possible - sample quicker, less opportunity for it to clot
- Be quick, avoid animal struggling- platelet clumps and blood clots may form if sampling takes too long
Sampling processing avoid:
- Inadequate mixing of specimen
- Haemolysed specimens (break down) (in vitro)
- Lipaemic (fatty) specimens (fasting)
- Clotted specimens – useless, need to take another sample. If send this to lab, have to call in patient again 1 day or so later!
- Platelet clumps (microscopy) -
- Diluted specimens – more problem with reptiles, dilution with lymph
- These are all possible sources of pre-analytical error!
- don’t shake
- look at all times to identify clotting
What calculations are routinely made on erythrocyte data?
- Mean corpuscular volume, MCV
- Mean corpuscular haemoglobin concentration, MCHC
- Mean corpuscular haemoglobin, MCH
How to work MCV, MCHC and MCH
- Mean corpuscular volume - ratio PCV/RBC. This gives the average size of the patient’s red cell in fL.
- Mean corpuscular haemoglobin - Concentration [Hb]/PVC. This gives the proportion of red cell mass that is attributed to Hb (mg/dL).
- Mean corpuscular haemoglobin - ratio Hb/RBC. This gives the average amount of Hb per red cell in pg.
What does it mean if Hb, PCV or RBC count are below or above reported reference interval for that species?
Anaemia or erythrocytosis
What dogs have blood cell abnormalities?
Greyhounds typically have higher Hb, Hct/PCV (same thing!) and RBC count.
Pups typically have much lower PCV than normal dog
Uses of RBC measurements:
- RBC count, Hb, PCV determine O2 carrying capacity of blood is adequate
- H2O has been lost from the circulation [dehydration]
- Anaemic - loss of blood oxygen carrying caoacity- present if any of the Red cell mass measurement (RBC count, PCV, Hb) below reference interval
- – - MCV - estimate of red cell size (corpuscular volume)
In anaemia how does MCV vary?
in 3 possible ways
- Raised
- Normal MCV -
- Reduced MCV
Talk in detail about anaemia MCV varying
- 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
- 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
- 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
when does Mean corpuscular haemoglobin concentration, MCHC, decrease
- 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
- in iron deficiency anaemia