DIAGNOSTIC VIROLOGY

Question 1

what can be detected in virology?

Answer 1

look for the virus itself

look for protein components of the virus ie. antigens

look for genetic components of the virus eg. genetic code of viral genome

look for the host responce ie antibody or cell responses to virus (most common method)

Question 2

what are the limitations of lab tests

Answer 2

assays may give false negative and false positive results

Question 3

what is the difference between sensitivity and specificity?

Answer 3

Sensitivity: the test’s ability to correctly identify positive samples

Specificity: the test’s ability to correctly identify negative samples

Question 4

what are the typical sample types for viral testing?

Answer 4

Throat swab, Nasopharyngeal aspirate (NPA), bronchoalveolar lavage (BAL), ET secretions – for detection of respiratory viruses by (IF or) PCR
Stools - for rotavirus, adenovirus & norovirus antigen detection (EIA) or PCR
Urine – for BK virus & adenovirus PCR
CSF - for herpes viruses and enteroviruses PCR
Blood (clotted) - for serology (antibody detection)
Blood (EDTA) - for PCR / viral load testing
Saliva – for serology &/or PCR (eg measles)

Question 5

what different procedures might be carried out in diagnostic virology?

Answer 5

virus isolation cell culture- takes a long time

electron microscopy using stool sample an d vesicle fluids - rarely used

immunofluorescence- direct detection of viral antigens

PCR - a method for amplifying specific RNA or DNA sequences (denature, primer annealing, chain elongation)- most commonly used