Virology lab Flashcards
What is it called if a rash has some areas that are raised and some that are flat?
Maculopapular
Macular = flat lesions
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 EM
Protein components- antigens on the virus (p24 antigen in HIV, surface antigen in HBV, etc)
Genetic components of the virus (DNA or RNA)- quantitative/qualitative tests available
Host response- antibody or cell response
Why are cell culture and electron microscopy not used much anymore?
They have been replaced by PCR (genome detection)
What is sensitivity?
A test’s ability to correctly identify positive samples –> affects the rate of false negatives
What is specificity ?
A test’s ability to correctly identify negative samples –> affects the rat eof false-positives
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
A sample of serum is taken a few weeks apart and you detect which one binds more strongly to the sample.
What does antibody avidity mean?
The strength with which antibodies bind to a specific antigen
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 antiretroviral susceptibility testing (HSV)