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Haemotology > Full blood count > Flashcards

Full blood count Flashcards

1
Q

abnormal results

A
  • Outside the normal range
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2
Q

normal range only includes

A
  • 95% of healthy population
    • 2.5% normal values above the range
    • 2.5% normal values below the range
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3
Q

results just outside the range may be

A

normal for that person

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4
Q

Significant fall in value

A

e.g. 160g/L to 115g/l (both in normal ranges- but still worrying)

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5
Q

nromal rnage changes with

A
  • Age
  • Sex
  • Ethnicity
  • Co-morbidities
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6
Q

If you receive an a result you are not expecting….

A

repeat test and consider contacting haematologist

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7
Q

interpret abnormal haematology results in light of

A

clnical context and previous FBC

e.g. to spot acute/chronic change

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8
Q

sources of error

A
  1. speciment collection error
  2. delivery of speicimens to laboratory
  3. specimen analysis and result reporting
  4. responsive action
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9
Q

1) Specimen collection error

A
  • Specimen mixed up
  • Wrong blood in tube
  • Wrong bottle
  • Pooling samples
    • Adding blood from another tube to fill one up to the line
  • Poor technique- may activate (haemolytic) sample
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10
Q

2) Delivery of specimens to laboratory

A
  • Specimen delayed/not delivered
  • Wrong delivery method
    • Some need to be sent in the dark, on ice, body temp
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11
Q

3) Specimen analysis and result reporting

A
  • Specimen mix up
  • Incorrect clinical details
  • Wrong test requested/performed
  • Inherent test variability
  • Technical error
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12
Q

4) Responsive action

A
  • Results not reviewed
  • Reflex tests not carried out
  • Right result applied to wrong patient
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13
Q

how is the full blood count carried out

A

Measured using an automated test with a very high level of accuracy that uses an analysing machine that can process thousands of samples every day.

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14
Q

essential parameters of the FBC

A
  • Red blood cells
    • Indices
    • RCC
    • haemoglobin
  • Platelet count
  • White blood cells
    • Count
    • Full differential
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15
Q

FBC ANALYSER TECHNIQUE

A

uses Flow cytometry

  • hydrodynamic focusing
    • single file line of cells
    • pass through light beam
    • impedance counting
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16
Q

forward scatter=

A

size

the more scatter= the bigger the cell

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17
Q

Spectrophotometry

*

A
  • Amount of light absorbed by the sample proportional to amount of absorbent compound within it e.g. haemoglobin
    • Hypotonic solution to lyse cells
    • Use light of appropriate wavelengths
    • Use calibration curve to determine sample conc
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18
Q

Flow cytometry differential

A
  • Forward scatter= size
  • Side scatter
    • Mono/polymorphonuclear
      • A type of immune cell that has granules (small particles ) with enzymes that are released during infections, allergic reactions, and asthma
    • Intracellular complexity
      • Granules
    • Myeloperoxidase activity
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19
Q

what are WBC

A

also known as leukocytes, WBC are cells of the immune system that are responsible for protecting the body againsdt infections or foreign bodies

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20
Q

how are WBCs counted

A

RBC in a sample of blood are lysed and the majority of remaining cells are WBC.

These are counted automatically as they interrupt a beam of light/ elecrcial current whilst going through a narrow tube in a straight line

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21
Q

what causes an increase in WBC

A

infection, smoking, leucocytosis, immune system disorders

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22
Q

what causes a decrease in WBC

A

damaged bone marrow, antibiotics, chemothrrapy drugs

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23
Q

Red blood cells contain

A

haemoglobin, which gives blood its red colour. The primary role is to transport oxygen and carbon dioxide to and from tissue

24
Q

how are RBCs measured

A

measured in the same way as WBC Clight beam) but withou the lysis step.

In comparision to BRC there are very few WBC so it does not affect the RBC count signif

25
Q

what causes an increase in RBC

A

congenital causes, hypoxia, polycythaemia vera

26
Q

what causes an decrease in RBC

A

anaemia, internal/external bleeding, erythropoietin deficiency

27
Q

what is haematocrit (HCT)

A

fraction of the whole blood volume that consists of RBC

28
Q

how is haemocrit counted

A

multiply the mean cell volume by the number of RBC per litre

29
Q

what causes abnormal haemocrit

A

similar reasons to high/low RBC values

30
Q

what is haemoglobin concnetreation

A

the amount of haemoglobin the blood (g/L)

31
Q

how is haemoglobin conc measured

A

after red cells have been lysed froma. blood sample, the Hb is converted to a stable form and measured by a colorimeter

32
Q

what causes an abnormal increase in Hb

A

living at high altitudes, lung dysfunction (smoking, COPD)

33
Q

what causes an abnormal decrease in Hb

A

lack of dietary iron, vitamin B2 or folate ,bleeding , anaemia

34
Q

what is mean cell volume (MCV)

A

the average volume of red cells

35
Q

How is MCV counted

A

use a beam of light or an electric current, and assess the amount of either that is blocke dby the red cells

36
Q

what causes an abnormal MCV

A

macrocytic anaemia >100 fl

microcytic anaemia <80 fl

37
Q

mean cell haemoglobin (MCH)

A

a erage amount of hb in an individual RBC

38
Q

how is mean cell haemoglobin (MCH) counted

A

divide Hb conc by the number of red cells in a given volume of blood

39
Q

what causes an abnormal increase in mean cell haemoglobin (MCH)

A

macrocytic anaemia, insufficient vitamin B12 or folate

40
Q

what causes an abnormal decrease in mean cell haemoglobin (MCH)

A

microcytic anaemia, low iron levels

41
Q

platelets

A

a fragment of a megakaryocyte invovled in clottign

42
Q

how are platelets counted

A

measured the same way as red or white cells.

Platelets produce a much smaller signal (due to their smaller size) so can be easily distinguished

43
Q

what causes an increase in platelets

A

thrombocytosis, bone marrow disorders

44
Q

what causes an decrease in platelets

A

increased platelt destruction (ITP)

45
Q

reticulocytes

A

immature red blood celsl

46
Q

how are reticulocytes counted

A

stains and dyes are used which bind to rRNA (not present in mature cells)

47
Q

what causes an abnormal increase in reticulocytes

A

high altitudes, hameolytic anaemia, bleeding

48
Q

what causes a decrease in reticulocytess

A

aplastic anaemia and bone marrow failure

49
Q

what are differential white blood cells

A

analyses te numebr of didfferent white cells in a blood sample

  • neutrophils
  • lymphocytes
  • monocytes
  • eosinophils
  • basophils
50
Q

how are differential white blood cells counted

A

can use automated blood anaylser- if abnormalities are detected then they will need to be counted manually on a blood film

51
Q

what causes abnormal differential white blood cells

A

infection

allergic reactions

52
Q

packed cell volume (PCV)

A
  • Proportion of blood that is made up of RBC
  • Centrifuged blood allows visualisation
53
Q

what can overestimate Hb results

A
  • Turbidity (is the cloudiness or haziness of a fluid) of plasma can overestimate Hb measurement
54
Q

what can underestimate Hb results

A

in vitro haemolysis

55
Q

Red cell distribution width (RDW)

A
  • Variation in size of the RBC
  • If increased= anisocytosis (patient’s red blood cells are of unequal size. This is commonly found in anemia and other blood conditions.)
56
Q

Red cell distribution width (RDW) can be used to assess

A

anaemia

  • Increased in iron deficiency
    • First parameter to rise as iron stores fall
  • Usually normal in thalassaemia trait
  • Increased following transfusion
57
Q
A

Haemotology (12 decks)

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