6. FBC

Question 1

What factors can affect normal range?

Answer 1

Age
Sex
Ethnicity
Co-morbidities

Question 2

How should abnormal haematology results be interpreted?

Answer 2

Interpret in light of clinical context and previous FBC
E.g. acute/chronic change, explained by disease
Always ask, does it fit with the clinical scenario?

Question 3

What errors in pathology results can come from specimen collection?

Answer 3

Specimen mix up
Wrong blood in tube
Wrong bottle
Pooling samples
Poor technique

Question 4

What errors in pathology results can come from delivery of specimen to laboratory?

Answer 4

Specimen delayed/not delivered

Wrong delivery method

Question 5

What errors in pathology results can come from specimen analysis and result reporting?

Answer 5

Specimen mix up
Incorrect clinical details
Wrong test requested/performed
Inherent test variability (measurement uncertainty)
Technical error

Question 6

What are the concurrent parameters in the FBC?

Answer 6

Red cells - indices, RCC, haemoglobin
Platelets - count, size
White cells - count, full differential

Question 7

What does pink top EDTA do?

Answer 7

Stops blood coagulation

Question 8

What is spectrophotometry?

Answer 8

Amount of light absorbed by sample proportional to amount of absorbent compound within it
Used to measure haemoglobin
Hypotonic solution to lyse cells
Use calibration curve to determine sample concentration

Question 9

What is flow cytometry?

Answer 9

Hydrodynamic focussing
Single file line of cells pass through light beam
Impedance counting 
Forward scatter = size
More scatter = bigger cell

Question 10

What is flow cytometry differential?

Answer 10

Forward scatter is size
Side scatter is mono/polymorphonuclear, intracellular complexity (granules)
Myloperoxidase activity

Question 11

How is anaemia represented in blood sample?

Answer 11

Depressed hematocrit percentage

Question 12

How is polycythemia represented in blood sample?

Answer 12

Elevated hematocrit percentage

Can be caused by reduction in circulating plasma volume or increased RBC

Question 13

What is packed cell volume (PCV)?

Answer 13

Proportion of blood that is made up of RBC

Used to assess anaemia but more often polycythemia

Question 14

What is RCC used for?

Answer 14

Used for assessment of anaemia and erytrocytosis

• reduced in iron deficiency anaemia
• increased in thalassemia trait

Question 15

What is the mean cell volume (MCV)?

Answer 15

Mean RBC size, measured using amount of light scattered as they pass in a single file past a laser
Important parameter used to screen cause of anaemia

Question 16

What is red cell distribution width (RDW)?

Answer 16

Variation in size of the RBC
If increased = anisocytsis 
Used to help assess cause of anaemia
- increased in iron deficiency
- normal in thalassaemia trait
- increased following transfusion

Question 17

When is a blood film done?

Answer 17

When significant result outside of normal range, significant change within normal range, analyser thinks there are abnormal cells

Question 18

What is the process of making a blood film?

Answer 18

Small drop of blood spread onto glass slide, 1 cell thick
Fixed with methanol
Stained to enable visualisation under microscope

Question 19

What does hypochromia look like under microscope?

Answer 19

Less haemoglobin, more white in centre of cell

Question 20

What does schistiocytes look like under microscope?

Answer 20

Red cell fragments present

Question 21

What does a vitamin B12 deficiency look like under the microscope?

Answer 21

Oval macrocytes
Basophils stippling
Howell-Jolly bodies
Hypersegmented neutrophil
Circulating granulocytic precursors