Practical 2: Infection and Inflammation Flashcards
What does a white blood cell count determine
The concentration of white blood cells in the patient’s blood
What does a differential wbc count determine
The percentage of each of the five types of mature white blood cells
How are wbc counts done by hand
Using a microscope and a haemocytometer (counting chamber)
When are wbc counts done by hand
If the patient has very low counts
The patient has a condition known to interfere with an automated WBC count
Why might a WCC be elevated
(6)
Infection
Allergy
Systemic illness
Inflammation
Tissue injury
Leukaemia
Why might a WCC be low
(5)
Viral infections
Immunodeficiency states
Bone marrow failure
Chemotherapy
Leukaemia
What are some sources of error for WCCs when done by hand
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
What might cause interference in automated WCCs
Small fibrin clots -> if blood is taken poorly or EDTA
Nucleated RBCs
Platelet clumping immature white cells and unlysed rbcs
What is a blood film?
A monolayer of blood cells distributed with minimum distortion on a glass slide
What stain is used on a blood film?
Wright stain (Romanowsky stain)
What is a wright stain?
A polychromatic stain consisting of buffered solutions of methylene blue and eosin
What is variation in rbc size called?
Anisocytosis
What is variation in rbc shape called?
Poikilocytosis
What is variation in rbc shape and size called?
anisopoikilocytosis
What is a Howell-Jolly body
DNA remnant
What is basophilic stiplling
Denatured RNA
What are siderotic granules
Granules containing iron
What are Heinz bodies
oxidised denatured Hb
What is an ESR?
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
What happens to ESR in disease
(3)
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
What is infectious mononucleosis also known as?
Glandular fever
What is glandular fever?
An infectious illness that is caused by the Epstein-Barr virus
What is the main characteristic of mononucleosis
(4)
Lymphocytosis with at least 10% atypical lymphocytes (they are large and have corners)
Fever
Pharyngitis
Swollen lymph nodes
There are many tests for mononucleosis, what are these based off?
The detection of heterophile antibodies
What are heterophile antibodies
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
Heterophile antibodies may be the consequence of what?
Polyclonal B-cell infection by EBV
What stain do we use when measuring WBCs using a haemocytometer
Turk’s solution
What is the principle behind using Turk’s solution to measure WBCs
(3)
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
How do you use a haemocytometer?
(4)
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
Describe why the equation for WCC is (Nx20)/(0.4)
(4)
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
What sample do you need for the ESR
EDTA anticoagulated sample
What is the Romanowsky stain
A series of Blue/Red stains where the blue binds to acidic substances and the red binds to neutral or basic substances in cells
How do you fix you blood film
(6)
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
What test do we use for mononucleosis
ACCUSAY mono one-step antibody test
How does the ACCUSAY mono one-step antibody test work?
It uses direct solid-phase immunoassay technology for the qualitative detection of IM heterophile antibodies in human serum, plasma or whole blood
How do you carry out a mono one-step test
(2)
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
How much patient sample should you add to mono one-step test
25ul whole blood
10ul serum/plasma
How much developer should you add to mono-one step test?
2-3 drops
