S3) Full Blood Counts

Question 1

What percentage of healthy people are outside the normal range?

Answer 1

5% - 2.5% above and below

Question 2

Which factors cause the normal range to vary? (4)

Answer 2

Age

Sex

Ethnicity

Co-morbidities

Question 3

Why are FBCs interpreted in context of previous FBCs?

Answer 3

To show whether there has been an acute/ chronic change

Question 4

Errors:

Specimen collection (3)

Answer 4

Specimen mix up

Pooling samples

Poor technique

Question 5

Errors:

Specimen delivery (2)

Answer 5

Specimen delayed/ not delivered

Wrong delivery method

Question 6

Errors:

Specimen analysis and result reporting (2)

Answer 6

Wrong test requested / performed

Technical error

Question 7

Errors:

Responsive action (2)

Answer 7

Result not reviewed

Reflex tests not carried out

Question 8

What must be done to the sample before testing and why?

Answer 8

K-EDTA anticoagulated to chelate calcium ions and stop blood coagulation

Question 9

Which 3 analyser techniques are used?

Answer 9

Spectrophotometry

Flow cytometry

Flow cytometry differential

Question 10

What is packed cell volume (PCV/ haemotocrit)

When is it depressed/ elevated?

How is the PCV reduced?

Answer 10

The proportion of blood that is made up of RBCs

Depressed in anaemia, elevated in polycythemia

The PCV in polycythemia is reduced by venesection or drug treatment

Question 11

What is RCC?

When is it reduced or increased?

Answer 11

Red cell count - number of RBCs in a given volume of blood

Reduced in microcytic anaemia caused by iron deficiency and increased in microcytic anaemia caused by thalassemia

Question 12

What is the MCV?

What is it used to detect?

Answer 12

Mean cell volume - mean size of an RBC

Used to screen the cause of anaemia

Question 13

What is RDW?

When is it increased?

When is it normal?

Answer 13

Red cell distribution width - shows variation in the size of RBCs

Increased in anisocytosis (unequal width of cells), iron deficiency and following transfusion

Normal in thalassaemia

Question 14

What is MCH?

When is it reduced?

When is it normal/ increased?

Answer 14

Mean cell haemoglobin - average amount of haemoglobin in each RBC

Iron deficient

Macrocytic anaemias

Question 15

What is MCHC?

How is it calculated?

When is it increased?

When types of infections is it useful to identify?

Answer 15

Mean cell haemoglobin concentration

Hb/MCV x RCC

Spherocytosis

Viral or mycoplasma

Question 16

When would a blood film be requested? (3)

What is the process of taking a blood film?

Answer 16

Significantly outside normal range
Significant change
Abnormal cells - immature and unable to identify

Small drop of blood onto glass slide - 1 cell layer thick
Fixed with methanol
Stained to allow visualisation under microscope

Question 17

What do the following terms mean?

Micro/macrocytic

Hypo/hyperchromic

Answer 17

Small / large RBC

Less / more Hb

Question 18

What do the following terms mean?

Dimorphism

Answer 18

Two distinct populations of red cells

Question 19

What do the following terms mean?

Poikilocytosis

Answer 19

Abnormally shaped RBC

Question 20

What do the following terms mean?

Echinocytes, acanthocytes, keratocytes, schistiocytes

Answer 20

Spiculated cells

Question 21

What do the following terms mean?

Target cells

Answer 21

RBC with dark area in the middle

Question 22

What do the following inclusions mean?

Howell-Jolly bodies

Basophilic stippling

Pappenheimer bodies

Heinz bodies

Haemoglobin inclusions

Answer 22

DNA/ nuclear fragments

RNA inclusions

Iron inclusions

Denatured haemoglobin

Denatured haemoglobin H

Question 23

Which cells are detected in the WBC differential? (5)

Answer 23

Neutrophils

Eosinphils

Basophils

Lymphocytes

Monocytes

Question 24

Which conditions / substances affect platelet levels?

Answer 24

Infection, iron deficiency and drugs