Viral Diagnosis

Question 1

Purpose of viral diagnosis

Answer 1

Clinical management - treating patients who have disease

Public health management - being able to contain a disease

Health care provision - education on vaccination

Question 2

Samples taken for viral diagnosis

Answer 2

Blood, urine, salvia, cerebrospinal fluid, nasal swab

Question 3

Direct detection of viruses

Answer 3

Testing for the presence of a virus by testing for viral proteins or nucleic acids

Question 4

Hemadsorption

Answer 4

Red blood cells are added to patient sample. If virus is present, red blood cells will adhere to the sample cells.

Question 5

Hemagglutination

Answer 5

Red blood cells are added to a patient sample. If a virus is not present then the erythrocytes naturally clump together. If a virus is present, the erythrocytes are unable to clump.

After knowing a virus is present, a specific antibody can be added to the sample. If the red cells clump then that allows identification of the virus based on what antibody was used.

Question 6

Sandwich ELISA

Answer 6

1. Plate coated in blocking buffer and capture antibody
2. Patient sample added (contains antigen)
3. Plate washed to remove unbound antigen, then a defection antibody is added which has a biotin molecule bound to it
4. Plate is washed again to remove unbound detection antibody then HRPO is added which has an avidin molecule bound to it
5. Substrate is added, changes from colourless to yellow in presence of HRPO

2-5 times more sensitive than indirect ELISA and has high specificity

Question 7

Indirect detection

Answer 7

Testing for the presence of specific antibodies and if we have a raised immune response.

This method doesn’t identify between past and recent exposures.

Question 8

Indirect ELISA

Answer 8

1. Antigen is bound to well
2. An unlabelled primary antibody binds to the antigen
3. A secondary antibody is bound to the first. This antibody is linked to an enzyme
4. Substrate is added which turns the solution coloured, indicating a positive result

Economical, however takes a long time to run

Question 9

Latex agglutination

Answer 9

Latex particles are added to a sample suspected to contain antigens.

If the antigen is present, latex beads clump together. If not, the latex beads spread out and all we can see is milky liquid.