Serology And Rapid Tests BLOCK 6 Flashcards
What do serology direct tests target
Antigens
+ in viral window
What do serology indirect tests indicate
Target antibodies
Negative in viral window
Acute infection
Antigen (pathogen), or IgM, or >4 fold increase between acute nad convalescent serum titers
Direct fluorescent antibody test
Flourescently labeled antibodies light up specific cells of micro organisms
Indirect fluorescent antibody tests
Used to demonstrate the presence of antibodies against a specific Ag
Direct fluorescent antigen
ID the antigen
Indirect fluorescent antibody
ID antibodies to the antigen
ELISA
- common tool to detect/measure Ag or Ab
- information rich: linked immunosorbant assay
Uses of ELISA
Antigen
Antibody
Other name of ELISA
EIA
Direct ELISA
Probes for antigen with a single labeled antibody
Indirect ELISA
Probes for antibodies to an antigen labeled antibody binds to unlabeled antibody
Sandwich ELISA
Antigen is sandwiches between two antibodies MOST COMMON
Pregnancy tests
What do indirect ELISAs identify
Antibodies
Use reporter enzyme
Purpose of control line on ELISA
Tells us the test worked
Agglutination
Particulate antigens (rbcs) + antibodies= agglutination
Soluble antigens + bound/particulate antigens=agglutination
Examples of ELISA
CSF/Urine
Fees
Throat (strep)
Serum is serially diluted and fixed antigen concentration is added to each tube (or increasing antigen concentrations are added to a fixed antibody concentration)
Precipitin curve
High levels of free antibody saturate antigens, but produce very little cross-linked Ag:Ab complexes
Antibody excess (prozone)
May test negative!!
No free Ag or Ab remains in solution after centrifugation of Ab:Ag complexes. Maximal precipitation
Equivalence
Need max crosslinking, equal Ag-Ab (equivalence)
Lattice theory
Why is prozone important?
Can have someone who is very sick, and still test negative!!
Antibody titer so high, agglutination test is negative
