Blood and faecal samples

Question 1

Laboratory diagnosis of African trypanosomes?

Answer 1

chancre fluid aspirate
lymph node aspirate
blood sample
marrow

Question 2

Concentration methods for African Trypanosomes?

Answer 2

Thick blood film
Woo concentration
Quantitative buffy coat-examined with fluorescence and microscope

Question 3

Filariasis MF detection lab diagnosis methods?

Answer 3

Blood smears
thick blood films
Knott’s concentration of a sample

Question 4

What is Knott’s concentration method?

Answer 4

Formalin added to blood, mixed and centrifuged, discard supernatant, add methylene blue, examine on slide

Question 5

What is faecal antigen detection?

Answer 5

Monoclonal enzyme immunoassays for detection of specific antigen in faecal specimens- can use an ELISA

Question 6

What are the two methods used for detecting parasites in faeces?

Answer 6

1. direct wet mount microscopic examination

2. use of a concentration method followed by microscopic examination

Question 7

What are the pros and cons of direct examination?

Answer 7

+
simple, quick, preserves trophozoites
-
often misses low numbers of eggs and cysts

Question 8

What are the pros and cons of concentration methods?

Answer 8

+
increases sensitivity, removes fatty debris, fixes in formalin so preserves sample
-
time consuming, additional equipment, costly

Question 9

What concentration techniques are there?

Answer 9

1. flotation technique

2. sedimentation technique

Question 10

Why might you get a false negative result from concentration methods?

Answer 10

1. Intermittent shedding of parasites so might not be in the sample
2. examining only one faecal sample
3. naturally low number of eggs shed in faeces
4. preparational errors

Question 11

What is a McMasters chamber used for?

Answer 11

faecal egg counting- debris sink to bottom, eggs float to surface
slide is examined on a microscope and number of eggs in each chamber is counted

Question 12

What culture methods can you use for Strongyloides?

Answer 12

• faecal charcoal cultures

- agar cultures(larvae moves through agar dragging bacterium with them)

Question 13

What is the kato-kaz technique?

Answer 13

used to examine stool

Question 14

What is the principle advantage of faecal concentration?

Answer 14

Increased sensitivity

Question 15

Why is the concentration of faeces recommended for diagnosis of S.mansoni?

Answer 15

Low numbers of ova are produced (200 a day)