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Year 2 Collin > Diagnostics 2- Virology Lab > Flashcards

Diagnostics 2- Virology Lab Flashcards

1
Q

Name 4 things that can be tested for in the virology lab

A
  1. Infectious virus
  2. Protein components of the virus(antigens)
  3. Genetic components of the virus
  4. Host response (antibody / cell responses)
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2
Q

Cell culture and electron microscopy are rarely done these days. They have been replaced by

A

PCR

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3
Q

Name 3 diagnostic methods used nowadays

A
  1. Antibody detection (serology - Enzyme Immunoassay (EIA))
  2. Antigen detection (Immunofluorescence - IF, or EIA)
  3. Genome detection (using PCR)
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4
Q

What are the limitations of lab tests

A

Give false negative and false positive results

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5
Q

What is sensitivity and specificity

A

Sensitivity = tests ability to correctly identify positive samples

Specificity = tests ability to correctly identify negative samples

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6
Q

Name 3 things that can be quantified during diagnostic Virology tests

A
  1. Antibody
  2. Antigen
  3. Genomes
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7
Q

What is viral load

A

Amount of virus present in blood/other fluids

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8
Q

Name 5 viruses that quantifying the genome is essential for diagnosing and monitoring in the immunocompromised

A
  1. HIV
  2. HCV
  3. HBV
  4. CMV
  5. EBV (glandular fever)
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9
Q

Genome sequencing may help direct treatment towards specific viruses. What 2 things may be involved with genome sequencing

A
  1. Genotyping

2. Antiviral resistance testing

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10
Q

Name 7 types of samples used and what they’re used for

A
  1. Throat swab/Nasopharyngeal Aspirate (NPA) / Bronchoalveolar lavage (BAL)/ ET secretions - used to detect respiratory viruses by PCR
  2. Stools - for rotavirus, adenovirus or notovirus, by PCR
  3. Urine - for BK virus by PCR
  4. CSF - for herpes viruses and enteroviruses by PCR
  5. Clotted blood - obtain serum for serology (antibody detection)
  6. Blood (EDTA to get plasma) - for PCR/Viral load testing
  7. Saliva - for PCR/serology
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11
Q

What is serology used for

A

To test for specific antibody viral antigen

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12
Q

Give 3 examples of serology tests used

A
  1. HIV serology - test for antibody and p24 antigen
  2. HBV surface Ag/b, eAg/b, core Ab, core IgM
  3. VZV IgG
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13
Q

Which antibody is the marker for acute/recent infection

A

IgM (approx 3 months)

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14
Q

Which antibody indicates past infection or immunisation

A

IgG

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15
Q

IgM has a low specificity. What does this mean

A

High rate of false positives

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16
Q

HIV serology testing is one of the main ways to test for HIV. It involves a 4th generation EIA that tests for which 2 things

A
  1. Ab
  2. p24 antigen

(Reactive species undergo confirmatory testing in 2nd assay to exclude false positives. Then confirmed positives undergo typing (HIV 1 vs HIV 2). Then repeat blood sample and EDTA blood for HIV viral load)

17
Q

What is the benefit of point-of-care testing

A

Immediate results for HIV or RSV - works with lab testing doesn’t replace it

(Less sensitive than lab testing)

18
Q

Virus isolation in cell culture is rarely used as a diagnostic means because it is time consuming and expensive. However, what is it still useful for?

A

Phenotypi antiviral susceptibility testing (HSV)

19
Q

Electron microscopy is also rarely used. What sample types does it work for?

A

Stool and vesicle fluids

20
Q

What is immunofluorescence used for?

A

Direct detection of viral antigens in clinical samples (e.g. respiratory viruses)

It is rapid and cheap but subjective - depends on quality of sample and technicians skill

21
Q

Name 3 respiratory tract infections

A

influenza, RSV, rhinovirus

22
Q

What does multiplex PCR allow

A

Testing multiple viruses in each tube

23
Q

What samples and tests are done is there is a suspected CNS disease (meningitis/encephalitis)

A
  1. CSF for PCR (HSV, VZV, Enterovirus)
  2. Stools and throat swab for enterovirus detection (by PCR)
  3. Blood for serology and/or PCR for West Nile / Japanese Encephalitis Virus and other arboviruses
24
Q

What things must be established in the clinical history for suspected CNS disease

A
  1. Meningitis (inflammation but no changes to brain i.e. no confusion) or encephalitis (inflammation with accompanying changes)
  2. Young child with febrile fits
  3. Immunocompromised
  4. Recent travel to endemic region
  5. In context of an outbreak
  6. SSPE (measles antibody index)
25
Q

What samples for diagnosis are taken if there is diarrhoea and vomiting

A
  1. Stool (preferred)
  2. Vomit (has lower yield)

PCR or antigen detection assays (EIA) done

26
Q

What do enteric viruses do?

A

Cause diarrhoea/vpmiting

e.g. norovirus, rotavirus, adenovirus, sapovirus, astrovirus

27
Q

What is PCR for and what is the starting block used?

A

Used for amplifying target RNA or DNA sequences

dsDNA is the starting block

28
Q

At what temperature is the RNA cycled (taq polymerase can withstand)

A

95 degrees

It is cycled through steps with various temperatures

29
Q

What are the sequencing applications of PCR?

A
  1. Genotyping
  2. Antiviral resistance testing
  3. Phylogenetic analysis
30
Q

What are the different types of PCR

A
  1. RT-PCR
  2. Real time PCR
  3. Multiplex PCR
  4. Viral load testing
  5. Sequencing (antiviral drug resistance testing)

Year 2 Collin (114 decks)

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