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Semester 2 MEH > L6: Interpreting the full blood count > Flashcards

L6: Interpreting the full blood count Flashcards

1
Q

What do we mean by abnormal results?

A

Results outside the ‘normal’ range
‘Normal’ only 95% population
–> some people outside will be normal, some people inside will be normal
Look for significant fall in value

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2
Q

What causes the normal range to change?

A

Age, sex, ethnicity, co-morbidities

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3
Q

What do abnormal results normally show?

A

Often reactive rather than reflective
Reactive–> to another physiological situation in the body
Reflective–> doesn’t usually reflect true haematological result

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4
Q

How would you know if the result is reactive or reflective?

A

Interpret–> clinical context and previous FBC if known

  • -> acute/ chronic change
  • -> is it explained by disease?
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5
Q

What errors can occur in pathology results?

A
  1. Specimen collection –> mix up, wrong bottle, pooling samples, poor technique, wrong blood in tube (incorrect labelling)
  2. Delivery of specimen to lab–> delayed/ not delivered, wrong delivery method
  3. Specimen analysis and result reporting–> Mix up, incorrect clinical details, wrong test requested/ perfomed, inherent variability (analysers not perfect), technical error
  4. Responsive action–> result not reviewed, reflex tests not carried out, right result wrong patient!
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6
Q

How is a full blood count performed?

A

Automated test–> high sample throughput, greater accuracy

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7
Q

What are the essential parameters?

A

Red cells–> indices, RCC, haemoglobin
Platelets–> Count
White cells–> count, full differential

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8
Q

What are the analyser techniques?

A

Spectrophotometry

Flow cytometry

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9
Q

How does spectrophotometry work?

A

Spectrophotometry–> amount of light absorbed proportional to amount of absorbent compound within–> measure amount of haemoglobin

  • -> hypotonic solution–> lyse cells
  • -> light of appropriate wavelength
  • -> calibration curve to determine sample concentration
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10
Q

How does flow cytometry work?

A

Hydrodynamic focussing –> single file line of cells

  • -> passes through light beam - perpendicular angle
  • -> impedance counting –> broken beam, one cell, stops beam hitting detector
  • -> forward scatter–> size of cell –> more scatter= bigger cell
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11
Q

How does flow cytometry differential work?

A

Same as normal flow cytometry
Look at side scatter–> bounces back >90 degree angle
Tells you complexity of environment–> mononucleated, polynucleated
Plot graph of forward scatter against side scatter–> shows size and complexity of cell–> work out what each cells is

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12
Q

What does myeloperoxidase activity show?

A

Present in granules (granulocytes)

If activity present –> granulocyte!

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13
Q

What does the packed cell volume (PVC/Hct) show?

A

The proportion of blood that is made up of RBC (L/L)
- centrifuge down
Assess anaemia and polycythemia (increased hematocrit)
Polycythemia reduced by venesection or drug treatment

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14
Q

What is the difference between true polycythemia and pseudopolycythemia?

A

True polycythemia–> increased red cell count

Pseudopolycythemia–> reduction in circulating plasma volume–> reduced plasma volume makes it look like more red cells

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15
Q

What other parameters can be tested to show if it is a true polycythemia or not?

A

Haemoglobin
RCC–> single RBC passed through detector
Mean cell volume –> amount of light scattered measured
Mean cell haemoglobin
Mean cell haemoglobin concentration
Red cell distribution width

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16
Q

What does haemoglobin show? What are the problems associated?

A

Amount of Hb mass/ plasma volume
Reference range–> varies sightly between labs but
>135g/L adult men
>115g/L adult women
>110g/L children (3/12- puberty)
>150g/L newborns
However not perfect as it is a concentration –> lower plasma level looks like increased RBC count therefore looks like more haemoglobin (Dehydration, acute bleed can affect result)
Turbidity of plasma–> affects amount of light absorbed–> over estimate
Heamolysis in vitro–> RBC destroyed whilst sample is being transported –> ↓ Heamoglobin

17
Q

What is red cell count (RCC)?

A

Number of red blood cells in a given volume of blood
(x10^12/L)
Assessment of anaemia, erythrocytosis etc
Microcytic anaemia
–> iron deficiency anaemia–> RCC reduced no iron less RBC produced
–> Thalassemia –> ↓ heamoglobin –> compensates by ↑RCC make more RBC to carry O2 (inherited)
Erythrocytosis
–> too many RBC made–> indicates true polycythemia

18
Q

What does the mean cell volume (MCV) show?

A

Mean size of RBC
High or low can give you lots of information
Most important parameter used to screen the cause of anaemia

19
Q

What does the mean cell haemoglobin (MCH) show?

A

Average amount of Hb in each RBC (pg)
MCH= Total amount of Hb/ Number fo RBC
Anaemia assessment

20
Q

What does the mean cell haemoglobin concentration (MCHC) show?

A

Mean concentration of Hb in RBC in a given volume
MCHC= (Hb/MCV) X RCC
Not common
Useful for cold agglutinins (RBC stick together when cold)

21
Q

What is the red cell distribution width (RDW) show?

A

Variation in size of the RBC
If increased = anisocytosis (patient RBC of unequal size)
Help assess cause of anaemia;
–> ↑ in iron deficiency
–> normal in thalassaemia trait
–> increased following transfusion (pt RBC and someone else RBC)

22
Q

What does the reticulocyte count show?

A

Measurement of the number of young erythrocytes (X10^9/L)
Identified using size and RNA count
Measure anaemia–> increased in lots of cases to compensate
decreases in haematinic deficiency–> not got what they need to make RBC and bone marrow deficiency

23
Q

What is a blood film? Why would it be done?

A

Thin layer of blood smeared onto a slide looked at under microscope

  • Significant result outside normal range
  • Significant change within normal range
  • Analysers think there are abnormal cells (immature cell, analyser unable to identify)
24
Q

What are some of the RBC terminology used to describe the size and colour of the RBC?

A 
Microcytic --> MCV --> small
Macrocytic--> MCV --> large
Hypochromic--> MCH --> pale, less Hb
Hyperchromic--> MCH --> Dense, more Hb in given volume
more on slide 25!
25
Q

What is the different terminology to describe the shaped of RBC?

A
  1. Anisocytosis–> different sized cells
  2. Dimorphism–> two distinct populations of cells
  3. Poikilocytosis–> abnormally shaped
  4. Spherocytosis–> Spherical RBC
  5. Elliptocytosis–> Elliptical RBC
  6. Irregular contracted cells–> Small dense RBC, not as round as spherocytosis
  7. Echinocytes, acanthocytes, keratocytes, schistiocytes –> spiculated cells
  8. Sickle cells–> crescent or sickle shaped
  9. Target cells–> RBC with dark area in middle of the area of central pallor
  10. Polychromasia–> ↑ immature RBC
26
Q

What inclusions can be seen in erythrocytes?

A

DNA/ nuclear fragments –> Howell-Jolly bodies
RNA Inclusions –> basophilic stippling
Rare–>
- Iron inclusion in cells –> Pappenheimer bodies
- Denatured haemoglobin –> Heinz bodies
- Golf ball cells - denatured Haemoglobin H –> Haemoglobin H inclusions

27
Q

What results would you expect to see in iron deficiency?

A

FBC and RBC indices–> ↓ Hb, MCV, MCH and MCHC
Reticulocyte count–> Low or normal (within the normal range)
FBC and RBC indicies–> ↑ RDW
Blood film –> Hypochromic, microcytic, pencil cells. few target cells

28
Q

What would you expect to see in Vit B12 Deficiency?

A

↓ Hb, RCC, Hct/PCV, Reticulocyte count
↑ RDW, MCH, MCV
macrocytic anaemia

29
Q

Why might WBC be measured? What do you measure?

A 
Increase sign of inflammation, infection, drugs etc
Measure 5 parts differentials 
--> neutrophils
--> eosinophils 
--> basophils 
--> lymphoytes 
--> monocytes 
nucleated RBC can be mistaken for lymphocytes
30
Q

What can platelet count show?

A

Platelets levels change very quickly
Can go higher or lower very quickly
Abberant parameter
Platelet clumping –> antibody activate in presence of EDTA used as anticoagulant in tubes
Clots in tube will reduce platlet count number

Semester 2 MEH (23 decks)

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