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clinical pathology > lecture 6 > Flashcards

lecture 6 Flashcards

introduction to haematology

1
Q

how is the haematological system assessed

A

packed cell volume, plasma protein, blood count, blood smear examination

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2
Q

what are the indications for assessment?

A

suspicion of: systemic inflammatory disorder, haemic neoplasia (leukaemia), anaemia, thrombocytopenia

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3
Q

where is blood sample taken?

A

jugular vein, to minimise damage to blood cells, only contraindication –> low platelet count (bleeding)

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4
Q

what needles

A

avoid small needles –> grren needle for dogs, blue for cats

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5
Q

predispositions before taking sample

A

clipping etc

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6
Q

what tube is preferred for haematology

A

EDTA –> chelates calcium, needed for clotting

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7
Q

citrate tube use

A

less platelet clumping in cats but not dogs

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8
Q

heparin tube use

A

poor staining of white blood cells (leukocytes) –> taking blood from small animal: can use the same sample for haematology

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9
Q

filling of tube

A

overfilling may allow clots to form, under-filling: altered red cell morphology, reduced packed cell volume, sample dilution

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10
Q

what if contaminate with EDTA?

A

artefactually increase potassium, decrease calcium levels

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11
Q

PCV def

A

gold standard measure of red cell mass, less affected by artefacts,

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12
Q

what to make sure of when PCV?

A

gentle mixing to avoid ‘decantification’ of cells

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13
Q

how do we measure PCV

A

(look at video on moodle)

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14
Q

microhaematocrit centrifuge

A

clay plug, red cells, buffy coat, white cells

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15
Q

how do we calculate pcv

A

PCV= A/B X100 where A is red cells and B is plasma + red cells

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16
Q

normal dog PCV

A

37-55%

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17
Q

normal cat PCV

A

26-45%

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18
Q

assessment of thickness of buffy coat

A

if > 1-2 mm then suggests increased white blood cell count –> inflammation or leukaemia

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19
Q

normal plasma colour

A

pale straw

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20
Q

red plasma

A

haemolysed sample –> free haemoglobin : in vitro or in the animal

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21
Q

yellow plasma

A

icterus

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22
Q

cloudy plasma

A

lipaemic –> endocrine disorders or…

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23
Q

how to get plasma protein concentration (PP)

A

refractometer: degree of light refraction of the sample proportional to the total quantity of solids in the plasma

24
Q

false increase in PP

A

lipaemia, increased urea (kidney failure), increased glucose (diabetes)

25
Q

what if low PCV?

A

low plasma protein –> haemorrhage OR normal or hogh plasma protein –> haemolysis or reduced production of RBC

26
Q

what if normal PCV

A

low plasma proteins –> low serum albumin OR high plasma protein –> high serum globulin (inflammatory response)

27
Q

what if high PCV?

A

low or normal plasma protein –> polycythemia OR high plasma protein –> dehydration

28
Q

caveat for analysing PCV and plasma protein

A

assume single pathological process: different things can affect these parameters independently

29
Q

erythrogram

A

red cell count

30
Q

leukogram

A

total white blood cell count

31
Q

thrombogram

A

number and size of platelets

32
Q

three main types of analysers

A

impedence analyser, flow cytometric analyser, quantitative buffy coat analyser

33
Q

impedence analyser mechanism

A

cells passed through electric current –> cells passing trhough electric current causes pusle –> pulse height related to cell size and frequency related to cell number –> cells are then lysed –> white cell count measured after red cell lysis –> cell-specific lysing solutions added to allow differentiation of leukocytes: granulocytes, lymphocytes, monocytes

34
Q

measured parameters of impedence analyser

A

RBC…

35
Q

haematocrit calculation (RBC mass) HCT

A

RBCxMCV/1000

36
Q

mean cell haemoglobin MCH

A

HGBX10/RBC

37
Q

mean cell haemoglobin concentration

A

HGB/HCT

38
Q

what if haematocrit is not within 2-3% of PCV

A

PROBLEM

39
Q

what measure os gold standard?

A

PCV

40
Q

potential errors of impedence analysers

A
  • red blood cells and platelets differentiated based on size –> erros with large platelets
  • white blood cell count: falsely increased if nucleated red cells are present, should always check blood smear
  • three part leukocyte differential count often inaccurate, esp if morphological changes, should always check smear
41
Q

flow cytometric based analyser mechanism

A

stream of cells through laser beam –> scatter –> low angle scatter correlates with cell size + high angle scatter correlates with cell granularity and internal complexity

42
Q

advantage of flow cytometric analyser

A

better differentiates red cells and platelets, can differentiate between types of leukocytes, can identify and count reticulocytes

43
Q

drawbacks of cytometric analyser

A

still prone to errors if morphological changes occur, often flags error

44
Q

quantitative buffy coat analyser mechanism

A

blood drawn into microhaematocrit tube and centrifugal force used to separte red blood cells etc, tube contains fluorescent markers

45
Q

problems with buffy coat analysers

A

rely on many assumtions so possible source of errors eg if cell sizes are abnormal

46
Q

advantages of buffy coat analyser

A

calculate platecrit rather than platelet count –> better indication of platelet mass

47
Q

blood smear examination use

A

validate results of automated CBC, identify morphological changes in the smear, band neutrophils classified as monocytes , morphological changes may be present before changes in cell numbers

48
Q

important when making smear

A

to make it fresh otherwise cells in the tube start to degenerate whilst if do smear fresh and allow cells to air dry then the morphology will be preserved

49
Q

blood smear preparation

A

use microhaematocrit tube –> place small drop of blood –> spreader slide in front of blood at an angle –> push spreader slide forward in one continuous motion to smear blood

50
Q

blood smear examination

A

look at feathered edge at low power (10x lens) –> platelet clumps, large cells, microfilaria

51
Q

what can you see in monolayer

A

50% of red cells touching each other,

52
Q

what can you see at high power (100x): platelets

A

platelets, number of platelets in hpf, average of 5, normal<15 per hpf,

53
Q

erythrocytes at high power

A

normal red cells, round in shape, colour –> polychromatophils, hypochromasia, lack central pallor, agglutination?, variation in size/shape, nucleated RBCs

54
Q

leukocytes at high power

A

examine in ‘zigzag’ pattern, count 100 cells and number each type, compared with automated, check morphology and size

55
Q

leukocytes

A

neutrophils (predominant), lymphocytes (sometimes predominant in cattle), monocytes, eosinophils, basophils

clinical pathology (3 decks)

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