Practical 2: Infection and Inflammation

Question 1

What does a white blood cell count determine

Answer 1

The concentration of white blood cells in the patient’s blood

Question 2

What does a differential wbc count determine

Answer 2

The percentage of each of the five types of mature white blood cells

Question 3

How are wbc counts done by hand

Answer 3

Using a microscope and a haemocytometer (counting chamber)

Question 4

When are wbc counts done by hand

Answer 4

If the patient has very low counts

The patient has a condition known to interfere with an automated WBC count

Question 5

Why might a WCC be elevated
(6)

Answer 5

Infection

Allergy

Systemic illness

Inflammation

Tissue injury

Leukaemia

Question 6

Why might a WCC be low
(5)

Answer 6

Viral infections

Immunodeficiency states

Bone marrow failure

Chemotherapy

Leukaemia

Question 7

What are some sources of error for WCCs when done by hand

Answer 7

Due to variance in the dilution of the sample and the distribution of cells in the chamber, and the small number of cells that are counted

Question 8

What might cause interference in automated WCCs

Answer 8

Small fibrin clots -> if blood is taken poorly or EDTA

Nucleated RBCs

Platelet clumping immature white cells and unlysed rbcs

Question 9

What is a blood film?

Answer 9

A monolayer of blood cells distributed with minimum distortion on a glass slide

Question 10

What stain is used on a blood film?

Answer 10

Wright stain (Romanowsky stain)

Question 11

What is a wright stain?

Answer 11

A polychromatic stain consisting of buffered solutions of methylene blue and eosin

Question 12

What is variation in rbc size called?

Answer 12

Anisocytosis

Question 13

What is variation in rbc shape called?

Answer 13

Poikilocytosis

Question 14

What is variation in rbc shape and size called?

Answer 14

anisopoikilocytosis

Question 15

What is a Howell-Jolly body

Answer 15

DNA remnant

Question 16

What is basophilic stiplling

Answer 16

Denatured RNA

Question 17

What are siderotic granules

Answer 17

Granules containing iron

Question 18

What are Heinz bodies

Answer 18

oxidised denatured Hb

Question 19

What is an ESR?

Answer 19

When anticoagulated blood is allowed to stand in a narrow vertical glass tube, undisturbed for a period of time, the RBCs, under the influence of gravity, settle out of the plasma

The rate at which they settle is measured as the number of milimeters of clear plasma present at the top of the column after one hour

Question 20

What happens to ESR in disease
(3)

Answer 20

RBCs are negatively charged

In disease the rbc’s negative charge is reduced which causes them to come together and form rouleux

Rouleaux falls faster

Question 21

What is infectious mononucleosis also known as?

Answer 21

Glandular fever

Question 22

What is glandular fever?

Answer 22

An infectious illness that is caused by the Epstein-Barr virus

Question 23

What is the main characteristic of mononucleosis
(4)

Answer 23

Lymphocytosis with at least 10% atypical lymphocytes (they are large and have corners)

Fever

Pharyngitis

Swollen lymph nodes

Question 24

There are many tests for mononucleosis, what are these based off?

Answer 24

The detection of heterophile antibodies

Question 25

What are heterophile antibodies

Answer 25

Antibodies with low affinity IgM antibodies with broad specificity for predominantly carbohydrate antigens that can react with molecules found on the surface of a number of nonhuman erythrocytes

Question 26

Heterophile antibodies may be the consequence of what?

Answer 26

Polyclonal B-cell infection by EBV

Question 27

What stain do we use when measuring WBCs using a haemocytometer

Answer 27

Turk’s solution

Question 28

What is the principle behind using Turk’s solution to measure WBCs
(3)

Answer 28

Turks solution contains a stain (gentian violet) and 6% acetic acid

Gentian blue stains the wbcs

Red cells are destroyed by the hypotonic solution plus acetic acid

Question 29

How do you use a haemocytometer?
(4)

Answer 29

Count the cells in the corners of the grid

Add all the results together = N

N x 20/0.4 ul = WCC/ul

(Nx20x10^6)/0.4 ul = WCC/ul

Question 30

Describe why the equation for WCC is (Nx20)/(0.4)
(4)

Answer 30

4 squares were used in counting = 4 mm2

The area under the coverslip has a height of 0.1mm

Volume counted = 4mm2 x 0.1mm = 0.4mm3 (0.4ul)

Blood was diluted 1 in 20

Question 31

What sample do you need for the ESR

Answer 31

EDTA anticoagulated sample

Question 32

What is the Romanowsky stain

Answer 32

A series of Blue/Red stains where the blue binds to acidic substances and the red binds to neutral or basic substances in cells

Question 33

How do you fix you blood film
(6)

Answer 33

Allow film to fully dry

5 dips in methanol (fixative)

12 dips in Eosin (stain A)

2 dips in buffered distilled water

5 dips in Methylene blue (stain B))

5 dips in buffered distilled water

Question 34

What test do we use for mononucleosis

Answer 34

ACCUSAY mono one-step antibody test

Question 35

How does the ACCUSAY mono one-step antibody test work?

Answer 35

It uses direct solid-phase immunoassay technology for the qualitative detection of IM heterophile antibodies in human serum, plasma or whole blood

Question 36

How do you carry out a mono one-step test
(2)

Answer 36

The sample is added to the sample window and if IM-specific heterophile antibody is present in the sample it will be captured by the antigen band (bovine erythrocyte extracts) impregnated in the test membrane

The developer solution is then added to the sample well and the test/control antigen band can be visualised

Question 37

How much patient sample should you add to mono one-step test

Answer 37

25ul whole blood

10ul serum/plasma

Question 38

How much developer should you add to mono-one step test?

Answer 38

2-3 drops