Virology Lab COPY Flashcards
Describe the ideal virological test
High specificity Sensitive Rapid Non-invasive Cost-effective
What can the virology lab be useful in detecting
Infectious virus
Protein components/antigens of the virus
Genetic components of the virus
The host response
Give some examples of diagnostic methods
Cells culture Electron microscopy Antibody detection (serology, EIA) Antigen detection (IF, EIA) Genome detection (PCR)
What are the limitations of diagnostic methods such as assays
All assays give rise to false negative and false positive results
What is sensitivity
The test’s ability to correctly identify positive samples
What is specificity
The test’s ability to correctly identify negative samples
Give examples of other diagnostic methods
Quantification of antibody or antigens Serotyping (eg HIV) Quantification of genomes – “viral load” Genome sequencing Genotyping Antiviral resistance testing
What is quantification of genomes useful for
Essential for diagnosis and monitoring of HIV, HBV and HCV, and also for CMV and EBV in the immunocompromised)
What samples are used for detection of respiratory viruses
Throat swab
Nasopharyngeal aspirate (NPA)
bronchoalveolar lavage (BAL)
ET secretions
Give examples of typical samples used
Stools Urine CSF Blood (clotted) Blood (EDTA) Saliva
What can stool and urine samples be used for
Stool - rotavirus, adenovirus, norovirus antigen detection (EIA) or PCR
Urine - BK virus and adenovirus PCR
What can CSF and blood (clotted and EDTA) samples be used for
CSF - for herpes viruses and enteroviruses PCR
Blood (clotted) - for serology (antibody detection)
Blood (EDTA) - for PCR / viral load testing
What can saliva samples be used for
Serology and PCR e.g. measles
Compare IgM and IgG
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
Describe serology testing
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