Practical 2: Exam Notes 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 wbcs
Why might a WBC count be elevated
Infection
Allergy
Systemic illness
Inflammation
Tissue injury
Leukaemia
Why might a WBC count be low
Viral infections
Immunodeficiency states
Bone marrow failure
Chemotherapy
Leukaemia
What is a blood film
A monolayer of blood cells distributed with minimum distortion on a glass slide
What stain is used for blood films?
Wright Stain (Romanowsky stain)
What is the principle behind the Wright stain
its a polychromatic stain consisting of buffered solutions of methylene blue and eosin
Define anisocytosis
Variation in rbc size
Define poikilocytosis
Variation in rbc shape
What is a Howell-Jolly body
DNA remnant
What is basophilic stippling
Denatured RNA
What are siderotic granules
Granules containing iron
What are Heinz bodies
Oxidised denatured haemoglobin
Define ESR
(2)
The time taken for RBCs to settle out of the plasma in an anticoagulated blood sample which is left standing upright
The rbcs settle out of plasma under the influence of gravity when allowed to stand for a period of time
What are schistocytes and when might you see them?
Fragments of rbcs
Seen in thalassaemia or megaloblastic anaemia
In what diseases would ESR be used as a means of monitoring the condition?
(3)
Systemic lupus erythematosus
Temporal arthritis
Systemic vasculitis
How does disease affect ESR?
(2)
Normal rbcs are negatively charged which keeps them separated from each other
In disease this negative charge is reduced -> consequent formation of rouleaux which will fall quicker
What is the basis of mononucleosis detection?
Tests are based on the detection of heterophile antibodies
What are heterophile antibodies?
Antibodies produced against poorly defined antigens and that they are generally “weak” antibodies with broad specificity for carb antigens that can react with molecules found on the surface of nonhuman erythrocytes
They may be the consequence of polyclonal B-cell infection by EBV
What stain do we use for our WCC and what is the principle behind this stain?
(4)
Turk’s solution
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 the haemocytometer?
(4)
Count the wbcs you see in the four outer corners of the haemocytometer
Add them all together to give you N
(N x 20)/ 0.4 ul = ul
(N x 20 x 10^6) / (0.4) = L
