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L - S Haem > Red Cell Parameters > Flashcards

Red Cell Parameters Flashcards

1
Q

What are the parts of a haematology report?

A
  • eryhtron
  • leukon
  • thrombon
  • morphology
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2
Q

What are we looking for when assessing red cells?

A
  • Red cell mass (PCV/Hct, RBCC, Hgb)
  • Evidence for effective and appropriate erythropoiesis (size and colour (MCV, MCHC) & reticulocyte count)
  • Red cells size and variation (MCV, RDW)
  • Red cell haemoglobinisation (colour) MCHC
  • Red cell shapes and inclusions (Smear)
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3
Q

What is the difference between relative and absolute polycythaemia?

A
  • Relative: Apparent increase in RBC due to a decrease in fluid in circulation (often increase in total protein and albumin)
  • Absolute: True increase in RBC mass due to increased RBC production/release (usu polychromasia, anisocytosis and reticulocytes)
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4
Q

What do PCV, RBCC and Hgb measure?

A

Red cell mass and oxygen carrying capacity - usually increase and decrease in line with one another

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5
Q

Why can PCV be wrong?

A
  • RBCs miscounted (mistaken for platelets or aggregated into pairs and triplets)
  • MCV misleading (cell shrinkage or swelling during transport, tube filling or because of osmotic effects in machine)
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6
Q

How is PCV calculated?

A

PCV = MCV x RBCC

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7
Q

Why do we sometimes see high MCHC results?

A
  • Not physiological to cram more Hgb into red cells than they will take
  • Haemolysis (sample handling or intravascular)
  • Lipaemia
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8
Q

Why are MCV results sometimes misleading?

A
  • Swelling of transport
  • Mis-identification – pairs and triplets, cross over with large platelets
  • Cell shrinkage or expansion in sample e.g. hyperosmolar
  • Will impact on calculated PCV/HCT
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9
Q

What is the rule of three?

A

Hct (%) approx. = Hgb (g/dL) x3 (+/- 3%)

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10
Q

How can we pick up rule of three error?

A

By looking up MCHC

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11
Q

What parameters is the classification of anaemia based on?

A

MCV and MCHC

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12
Q

What measures of anaemia are more sensisitve than MCV and MCHC?

A

Machine dot-plots and histograms more sensitive

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13
Q

What are the 3 common classes of anaemia?

A
  • normocytic normochronic
  • macrocytic hypochromic
  • microcytic hypochromic
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14
Q

Which anaemia class is associated with a classic iron deficiency?

A

Microcytic Hypochromic

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15
Q

What effect on parameters does polycythaemia have?

A

Increase in PCV, Hgb concentration and RBC count

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16
Q

What are the signs associated with relative polycythaemia?

A

“Dehydration” (water or acellular fluid loss):
[eg vomiting, diarrhoea, polyuria, extensive burns, adipsia, water deprivation]

Exercise, fear, excitement, severe pain - stress: Adrenaline secretion, splenic contraction and transient redistribution of RBC from the spleen to the circulation

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17
Q

What parameters are affected by relative polycythaemia?

A

PCV is increased
No increase in RBC production

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18
Q

How is relative polycythaemia resolved?

A

Resolves after rehydration or removal of cause of splenic contraction

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19
Q

What parameter change is associated with absolute polycythaemia?

A

Increase in RBC production

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20
Q

What are the 2 types of absolute polycythaemia?

A
  • primary
  • secondary
21
Q

What is primary polycythaemia?

A
  • rare myeloproliferative disorder
  • abnormal response of RBC precursors
  • Normal EPO levels
22
Q

What is associated with secondary polycythaemia?

A
  • Chronic tissue hypoxia of renal tissues (low arterial pO2) due to:
    heart/lung diseases, high altitude, thrombosis, constriction of renal vessels
  • Renal tumor or cysts [↑intra-capsular pressure]
  • Increased EPO
23
Q

What are reticulocytes?

A

Young (immature/non-nucleated) erythrocytes prematurely released to blood from the bone marrow in regenerative anaemias

24
Q

Why would we measure reticulocyte count?

A
  • Evaluation of erythropoiesis in bone marrow.
  • Differentiation of regenerative and non-regenerative anaemia.
25
Q

What do reticulocytes look like on romanowsky (routine) stain?

A

have “polychromatophil” appearance

26
Q

How are reticulocytes counted?

A
  • manual
  • automated (analysers)
27
Q

What is the absolute reticulocyte count?

A

observed % reticulocytes x RBC x 10

28
Q

What is a normal reticulocyte count in dogs?

A

Low number of reticulocytes (<1%)
Expect at least (>60x109/L) in regenerative anaemias

29
Q

What is a normal reticulocyte count in cats?

A

Low number of reticulocytes (0.2-1.6%)
Expect at least (>50x109/L) in regenerative anaemia

30
Q

What are the 2 kinds of reticulocytes in cats?

A

‘aggregate’ blue stained coarse clumping (0.5% of erythrocytes)
‘punctate’ small, blue stained dots (1-10%).
Kinetics of Aggregate vs Punctate means we only consider Aggregate in assessment of regeneration

31
Q

What is the normal count of reticulocytes in ruminants and horses?

A
  • Virtually no reticulocytes in normal blood;
  • Reticulocytes may not appear even in very severe anaemias in horses;
  • In cattle peak production 7-14 days post acute blood loss
32
Q

What species variation is there in RBCs volume?

A
33
Q

What species variation is there in RBC number?

A
34
Q

Which species is this blood slide typical of? why?

A

Dog
* Larger erythrocytes
* Uniform size
* Central pallor

35
Q

What species is this blood slide typical of? why?

A

cat
* Smaller erythrocytes
* Anisocytosis (variation in size)
* Scarce central pallor (less concave)

36
Q

What species is this blood slide typical of? why?

A

Ruminant
Anisocytosis and crenation

37
Q

What species is this blood slide typical of? why?

A

Horse
Rouleaux
(sedimentation tendency)

38
Q

What variations are there in RBCs within dog breeds?

A
  • macrocytosis in some poodles
  • akitas have unusually small erythrocytes and particularly high potassium content
  • greyhounds have high PCVs (0.55-0.6 L/L)
39
Q

What is poikilocytosis?

A

Variation in cell shape

40
Q

What can cause alteration in cell shape in RBCs?

A

abnormal erythropoeisis
specific organ dysfunction

41
Q

What are codocytes?

A

mexican hat cells - important in Fe deficiciency

42
Q

What are spherocytes?

A

Important in diagnosing IMHA

43
Q

What are acanthocytes?

A

Thorny spikey cells
Few irregular elongations of RBC border with rounded ends

44
Q

What are schistocytes?

A

Erythrocyte fragmentation

45
Q

What are echinocytes?

A

Small little even spikes along the outside

46
Q

What inclusions might we see in RBCs?

A
  • Howell Jolly bodies (nuclear remnant)
  • Basophilic stippling
  • Nucleated RBC’s
  • Infectious agents (Mycoplasma, Babesia, Viral inclusions)
  • Heinz bodies (crystallised haemoglobin)
47
Q

What are rouleaux formations?

A
  • Clustering, sticky, piling of RBCs
  • Normal finding in horses
  • Indicates inflammation in small animals
  • Relates to increased “stickiness” of plasma with increased globulin content
48
Q

What causes agglutination of RBCs?

A
  • IMHA
  • mismatched blood transfusion
49
Q

How to we differ rouleaux formation from agglutination?

A

To confirm agglutination:
Mix 1 drop of blood with 1 drop of saline
-> Agglutination will persist, rouleaux formation will disperse

L - S Haem (9 decks)

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