diagnostic virology Flashcards
what is detected
actual virus (rare)
antigens of virus, or genetic components of virus (DNA/RNA)
host response eg antibody antigen interaction
diagnostic methods
quantify antibody/antigen, or quantify genome (viral load)
serotyping eg HIV 1 or 2
genome sequencing
typical samples used
throat swob, bronchoalveolar lavage for respiratory viruses
stools/urine
CSF
blood (for serology or for viral load)
saliva
all samples used for PCR apart from for serology- PCR tests for DNA, serology tests for antibodies in blood
antibody testing
can look for IgM antibodies (last 3 months after disease onset) or IgG (last for whole life)
antibody avidity testing
those antibodies with low avidity will be washed away, as not bound strongly- avidity increases with time, so often used to DATE the disease
HIV testing
mostly use serology (elisa test)- then undergo serotyping (HIV 1 or 2), and look at viral load (amount of virus in blood)
point of care testing
done for viruses- drop of blood put on a stick (like pregnancy test)
electron microscopy/ culture and immunofluorescence
all rarely used, mainly PCR used now
detection of viral antigens- antibodies placed which are fluorescently labelled
CNS disease
meningitis/encephalitis- CSF used for PCR, STOOLS used for PCR as well, as well as BLOOD for PCR
can be HSV, VZV or enterovirus- depends on history eg travel to a certain country
real time PCR melt curve analysis
PCR products melt at different temp.s depending on virus
sensitivity vs specificty
sens- ability to correctly identify positive (ie should give few false positives)
spec- correctly identify neg (ie should give few false positives)
multiplex PCR
amplifies specific RNA/DNA sequences- multiplex can test multiple antigens from a sample ie 1st box for EBV, 2nd box for HIV
