Virology lab Flashcards
What is it called if a rash has some areas that are raised and some that are flat?
Maculopapular
What is a blotchy appearance rash typical of?
Measles
If the distribution of a rash is dermatomal, what is this typical of?
Shingles
What can virologists detect?
Infectious virus- virus isolation and electron microscopy
Protein components- antigens on the virus
Genetic components of the virus
Host response- antibody or cell response
Why are cell culture and electron microscopy not used much anymore?
They have been replaced by PCR
What is sensitivity?
A test’s ability to correctly identify positive samples
What is selectivity?
A test’s ability to correctly identify negative samples
What is a marker of recent infection?
IgM - IgG comes later on
What is essential for diagnosis and monitoring of HIV, HBV and HCV and also for CMV and EBV in immunocompromised?
Viral load- quantification of genomes
What typical sort of samples are used by virologists?
Throat swab, nasopharyngeal aspirate, bronchoaveolar lavage- detection of respiratory viruses by PCR
Stools- For rotavirus, adenovirus and norovirus antigen detection or PCR
Urine- for BK virus and 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 and or PCR
What is positive IgG with absent IgM consistent with?
Past infection or immunisation
What is antibody avidity testing used for?
Confirming a positive IgM result
What does antibody avidity mean?
accumulated strength of multiple affinities of individual non-covalent binding interactions, avidity is distinct from affinity, which describes the strength of a single interaction
HENCE TESTING FOR IgM BECAUSE OF PENTAMER STRUCTURE
How does antibody avidity change throughout infection?
Early on in course of infection, avidity is low
Then you get maturation of antibody response so avidity gradually increases over a period of 3-6 months
If you have high antibody avidity then it makes it unlikely that infection occured in last 3 months
What is virus isolation in cell culture still useful for despite being slow and time consuming?
Phenotypic antiviral susceptibility testing