Diagnostic Virology Flashcards Preview

MCD - Diagnostics > Diagnostic Virology > Flashcards

Flashcards in Diagnostic Virology Deck (21):

What is a maculopapular rash?

Some areas are raised and some areas are flat


What is a dermatomal distribution of a rash indicative of?

Shingles or herpes


What can be used in virus detection?

Virus isolation and electron microscopy to visualise the virus itself Protein components (antigens) Genetic components (RNA or DNA) The host response (antibody or cell responses)


What is the main method of virus detection?



What technique is used for antibody detection?

Enzyme immunoassay – detects antibodies and antigens


Define sensitivity.

Low rate of false negatives

The ability of the test to identify everyone with the disease


Define specificity.

Low rate of false positives

The ability of the test to identify everyone without the disease


What does quantification of the genomes allow assessment of?

Viral load - used in HIV


What is the difference between IgM and IgG in terms of when theirlevels rise following infection?

IgM is a marker of RECENT infection IgG rises later on in the infection and some remains after the infection has passed


What does positive IgG and absent IgM indicate?

Past infection or immunisation


What is targeted in the detection of HIV?

Antibody and p24 antigen


What other investigations are performed on people who are identified as HIV positive?

Typing (HIV 1 or HIV2) Repeat blood sample and EDTA blood for HIV viral load (for genotyping and baseline resistance testing)


What test is used to confirm a positive IgM result?

Antibody avidity testing


Describe how antibody avidity changes in infection.

Early on in the infection, avidity is LOW Then you get maturation of the antibody response so the avidity will increase over a period of 3-6 months If you have HIGH antibody avidity, then it is unlikely that the infection occurred in the last 3 months


What is immunofluorescence useful for?

Direct detection of viral antigens


What is the term given to the method of PCR that allows testing for more than one virus using a single test tube?

Multiplex PCR


What 4 things are sampled when testing for meningitis/encephalitis?

  • CSF
  • Stools​ and throat swab (for enterovirus detection)
  • Blood


What is sampled when testing for causes of diarrhoea/vomiting?

Stool (and vomit)


What must happen first before PCR is performed to identify the genome of an RNA virus?

The RNA must be reverse transcribed by reverse transcriptase to dsDNA dsDNA is the start point of PCR


Describe the process of PCR.

The dsDNA is denatured by heating it The primers then bind to the single stranded DNA and Taq polymerase joins complementary nucleotides to the template strand


What are the applications of sequencing viral genomes?

Antiviral resistance testing Phylogenetic analysis