unit 5 Flashcards
serology
study of blood serum (blood without clotting factor)
titer
tells us concentration based on dilution of blood
evaluate storage conditions for specimens received in laboratory for serologic diagnosis of infectious diseases
refrigerate up to 1 week then freeze at 20 degrees celsius
factors that affect antigen-antibody reactions
specificity, accessibility (able to detect), valency (# of binding sites), antibody structure (dimers etc.), concentrations (zone of equivalence), affinity (strength), avidity (capacity)
categories of serologic tests used to diagnose human disease
pricipitation, agglutination, etc.
principles of precipitation tests
soluble antigen and antibody bind in equal proportion to form insoluble immune complexes (this is what we measure)
postzone vs prozone
prozone –> antibody excess
postzone –> antigen excess
interpretation of the ouchterlony test
formation of three possible precipitant lines
arc (identity) –> identical Ag
spur (partial) –> common epitope)
intersect (non) –> unrelated Ag
fahey vs mancini quantitative assays
fahey (kinetic) –> standard curve to extrapolate; 18hrs
immunoelecrophoresis vs immunofixation
in immunofixation (more specific) you run sample in multipe lanes instead of just one
immunoblots vs dot blots
immunoblots: harder to read, electrophoresis performed to separate
dot blots: easier to read, electrophoresis not performed
nephelometry
measurement of light scattered by immune complexes
(more sensitive)
turbidimetry
measurement of light transmitted through immune complexes
chemiluminescence
chemical reaction that produces light –> on labeled Ab
flocculation test
used for syphilis testing
soluble antigen and antibody form precipitate –> small clumps of charcoal if Ab is present
direct agglutination
patient Ab binds to Ag found in bacteria
passive agglutination
antigen is artificially added to latex and will bind to patients Ab
reverse passive agglutination
antibody is artificially added to latex and will bind to patients Ag
agglutination inhibition tests
competition between precipitate and antigens for limited antibody sites
–> test antigen with patient serum, if no precipitate that means there are antibodies present
agglutination vs precipitation reactions
A: insoluble antigen; qualitative test
P: soluble antigen and antibody; qualitative and quantitative
direct vs indirect fluorescence assays
D: detect antigens in tissue when labeled antibody bind and show as fluorescent under microscope
In: detect unlabeled antigens using patients serum to bind if present and then labeled antibodies to bind to patients antibodies
principle and uses of flow cytometry
quantitative method that sorts cells telling us its size, components and identity
–>cells come down flow cell in single file, pass laser, and detectors sort
principles of labeled tests
enzyme attached to antibody, when binds and enzymatic change occurs there is a color change to signify positive test
mechanisms of how heterophile antibodies can affect immunoassays
heterophiles will bind to capture antibodies blocking binding sites
methods to minimize interference by cross reactive antibodies
dilution to ensure 1 antigen binds to multiple Abs
–> monoclonal ab (specificity)
conjugated antibody
labeled antibody with fluorescence
sensitivity
ability to correctly identify disease
specificity
ability to correctly identify patients that do not have disease
negative predictive value
measure of how likely a negative test result actually means no disease
positive predictive value
measure of how likely positive test result actually means there is disease
true positive
actual postive result
false positive
positive result that is actually false
true negative
negative result that is correct
false negative
negative result that is actually positive
