025 Laboratory Investigation of viral infection

Question 1

What is the main diagnosis method for Hep A?

Answer 1

IgA antibody test

Question 2

How would you detect viruses on tissue culture?

Answer 2

If there is a cytopathic effect e.g. forming syncinctium

Question 3

Which antibody test is used to diagnose acute infections and why?

Answer 3

IgM because they are the first line of defence and it gives a rapid diagnosis

Question 4

What are some main ways used to detect antibodies?

Answer 4

ELISA - a layer of antigobulin that has a colored tag when it attaches to the Fc receptor of antibodies that are bound to the antigen.
Neutralisation - directly blocking viral infectively in tissue culture, with absence of a cytopathic effect.
Latex agglutination - antigen covered latex beads. It is mixed with patient serum sample. If beads clump together, then there is antibody present. It is compared to a point of care test.

Question 5

Which antibody test is used to diagnose vaccination immunity ?

Answer 5

IgG

Question 6

Why might detecting virus antibodies not be appropriate in diagnosing some individuals?

Answer 6

They could be suppressed
It can be passively acquired in newborns
It could be during the window period in which virus infection precedes antibody production.

Question 7

Which antibody test is used to diagnose persistant infections and why?

Answer 7

IgG because this lasts in the blood for a long time. It reflects past exposure.

Question 8

What are some main ways to detect antigens?

Answer 8

ELISA - similar to antibody detection
Latex agglutination - fixing antibody to latex beads and testing for agglutination by antigen.
Immunofluorescent tests - when acetone is used to break down the membranes, and antibody with fluorescent label is added. This can be seen with UV microscope.

Question 9

How do you diagnose HIV and the window period?

Answer 9

p24 antigen and IgG.