Practical 5: Exam Notes

Question 1

What is malaria?

Answer 1

A mosquito born haemolytic febrile illness caused by the Plasmodium parasite.
Transmitted by the female anopheles mosquito

Question 2

What are the three tests used to diagnose malaria

Answer 2

Rapid diagnostic tests

Thick film with field’s stain

Thin film with Giemsa stain

Question 3

Why do we use a Thick film

Answer 3

Used to detect the presence of the parasite
Useful in low grade parasitaemias

Question 4

Why do we use a thin film

Answer 4

Used to determine % parasitaemia count
Used to determine species of parasite
Used to note the different stages of development seen

Question 5

What are the five identifiable stages of malaria in a blood film

Answer 5

Ring forms (early trophozoite)

Early schizont (late trophozoite)

Schizont

Merozoites

Gametocyte

Question 6

How do you determine percentage parasitaemia

Answer 6

Count all the parasite cells in the big box

Count all the cells in the small box

Count until you have about 115 in the small boxes then x9

(Parasite cells/ Normal cells) x 100

Question 7

What is sensitivity and what is the equation for it

Answer 7

A test’s ability to determine the patient cases correctly

True positive/ (true positive + false negative)

Question 8

What is specificity and what is the equation for it?

Answer 8

A test’s ability to determine the healthy cases correctly

True negative / (true negative + false positive)