Immunology: Common Lab Tests Flashcards
What do immunologic tests look for?
Specific infectious agents
Evaluate sensitivity & specificity
Sensitivity
-Able to correctly identify all animals that are truly positive for a give reaction procedure
-How much of the antigen or antibody needs to be present before the color change
How sensitive is the test
Specificity
Measures the number of false positives produced with a given reaction procedure
Can I determine exactly which protein this is?
Is there any cross reaction with a similar antigen?
Which test has 100% sensitivity & 100% specificity?
No test exists
What does the heartworm antigen test need to become positive?
A minimum of 3 adult female worms
What sample do nearly all immunologic tests require?
Serum or plasma
What sample should not be sent to the diagnostic lab?
Whole blood
What route of collection is preferred?
Vacutainer to prevent hemolysis
Red top if serum
Lavender top if plasma unless otherwise noted
Who has strict requirements and what must be done carefully and followed
The reference laboratories
The directions
How should serologic samples be handled?
Clot for 20 to 30 minutes at room tep
How long do you centrifuge serum samples for?
10 minutes at 1500 rpms or greater
What sample do you centrifuge immediately after collection?
Plasma
What do you pipette?
Serum or plasma into a transfer tube and label
Can you freeze the serum or plasma samples?
Yes or refrigerate
What is humoral immunity?
Antigen/antibody complexes
What are the tests that look for antigen/antibody complexes (humoral immunity)
ELISA
CELISA
Latex Agglutination
Rapid Immunomigration & Immunochromatography
ELISA
Enzyme-linked immunosorbent assay
What is the most commonly used test in the veterinary practice?
ELISA
What is an ELISA test?
Accurate way to detect specific antigens
viruses, bacteria, parasites, hormones
What does the ELISA test test for?
Antigen in serum
What does the test kit contain?
A specific antigen
What are some examples of ELISA tests?
Heartworm Feline leukemia FIV Parvo Progesterone
What is bound to the well walls, the test tray or the plastic wand of the ELISA test?
Monoclonal antibodies
What happens in the ELISA test if the antigen is present?
It binds to the antibody & to a second enzyme-labeled antibody
What happens if the antigen is present in the patient?
The antigen/antibody complexes will form and the enzyme will react and cause a color change
What has to happen for the ELISA test to be positive?
The antigen needs to be present in the body and the antigen/antibody complexes need to be formed
What is another ELISA test option
The test contains the specific antigen and then you are looking for the antibody in the sample from the patient
What does it mean if the antigen is present?
We know it is a current infection
What type of ELISA test is run on cats with suspected heartworm disease
The antibody test to look for the immune response because they might not have 3 adult female heartworms
What is the problem with the ELISA antibody test that contains the antigen?
You don’t know if it is a current infection or if they were previously infected
CELISA tests
Competitive Enzyme-linked immunosorbent assay
What is the CELISA test used for?
Equine infectious anemia
What does the CELISA test use?
Patient antigen
enzyme-labled antigens as well as monoclonal antibodies
What varies with antigen concentration?
Intensity of color
The more antigen present the more color you get
What do we use the Latex agglutination test for?
Bovine brucellosis
What does Latex agglutination test use?
Small, spherical latex particles that are coated with an antigen suspended in water
What do the spherical particles do if the antibody is present?
Cause clumping
RIM
Rapid Immunomigration or Immunochromatography
AKA lateral flow immunoassy
What do RIM tests use?
Colloidal gold, enzymes, and color reagents or agglutinated latex particles
What are present in the membrane of the test cassette where the sample is applied?
Antibodies
Is there rinsing or reagent used in RIM tests?
No
What do positive RIM results look like?
Two areas of color:
The test result and control
What are examples of RIM tests
Heska heartworm Witness FeLV (feline leukemia virus)
How does a RIM test different from an ELISA test
No diluent is needed, just the sample