Virology Lab COPY Flashcards

1
Q

Describe the ideal virological test

A
High specificity 
Sensitive
Rapid
Non-invasive
Cost-effective
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2
Q

What can the virology lab be useful in detecting

A

Infectious virus
Protein components/antigens of the virus
Genetic components of the virus
The host response

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3
Q

Give some examples of diagnostic methods

A
Cells culture
Electron microscopy 
Antibody detection (serology, EIA)
Antigen detection (IF, EIA)
Genome detection (PCR)
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4
Q

What are the limitations of diagnostic methods such as assays

A

All assays give rise to false negative and false positive results

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5
Q

What is sensitivity

A

The test’s ability to correctly identify positive samples

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6
Q

What is specificity

A

The test’s ability to correctly identify negative samples

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7
Q

Give examples of other diagnostic methods

A
Quantification of antibody or antigens
Serotyping (eg HIV)
Quantification of genomes – “viral load”
Genome sequencing
Genotyping
Antiviral resistance testing
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8
Q

What is quantification of genomes useful for

A

Essential for diagnosis and monitoring of HIV, HBV and HCV, and also for CMV and EBV in the immunocompromised)

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9
Q

What samples are used for detection of respiratory viruses

A

Throat swab
Nasopharyngeal aspirate (NPA)
bronchoalveolar lavage (BAL)
ET secretions

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10
Q

Give examples of typical samples used

A
Stools
Urine
CSF
Blood (clotted)
Blood (EDTA)
Saliva
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11
Q

What can stool and urine samples be used for

A

Stool - rotavirus, adenovirus, norovirus antigen detection (EIA) or PCR

Urine - BK virus and adenovirus PCR

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12
Q

What can CSF and blood (clotted and EDTA) samples be used for

A

CSF - for herpes viruses and enteroviruses PCR
Blood (clotted) - for serology (antibody detection)

Blood (EDTA) - for PCR / viral load testing

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13
Q

What can saliva samples be used for

A

Serology and PCR e.g. measles

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14
Q

Compare IgM and IgG

A

Both present in acute phase of disease
IgM- 3 months
IgG - lifelong
IgM often gives false positives - avidity testing used to test strength of antibody binding

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15
Q

Describe serology testing

A
HIV - antibody + p24 antigen
Hep A - IgM and IgG
HBV - surface Ag/Ab, eAg/eAb, core Ab, core IgM
HCV - antibody, core antigen 
CMV/EBV - IgM and IgG
VZV - IgG
MMR - IgM, IgG
Parvovirus - B19 - IgM, IgG
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16
Q

Describe HIV serology

A

All reactive samples undergo confirmatory testing in a second assay to exclude specific reactivity (false +ve)
Confirmed positive -> typing
Repeat blood sample + EDTA blood for HIV viral load

17
Q

Describe virus isolation in cell culture

A

Slow and time consuming and therefor expensive

Useful for phenotypic antiviral susceptibility testing (HSV)

18
Q

Describe electron microscopy

A

Viruses are small but can be visualised using an electron microscope.
Sample types of stool and vesicle fluids
Rarely used

19
Q

Describe immunofluorescence

A

Still occasionally used for the direct detection of viral antigens in clinical samples (DIF) (e.g. respiratory viruses)
Rapid and inexpensive but subjective and very dependent on the skill of the technician and the quality of the sample