What is sensitivity?
- the detection of even minute quantities of antibodies or antigens in a specimen
- reflects the degree to which a test will detect every positive person
What is specificity?
- the property of a test to focus on only certain antibody or antigen
- does not react with unrelated or distantly related antigens
- the degree to which a test does not falsely detect who do not have a condition
What is the process for agglutination tests?
- Antisera containing antibodies against the blood group antigens on red blood cells are mixed with a small sample of blood and read for the presence or a sense of clumping
- Used by blood banks to determine ABO and Rh (rhesus) blood types in preparation for transfusions
What is the process for precipitation tests?
- The soluble antigen is precipitated (made insoluble) by an antibody
- antiserum has been carefully laid over an antigen solution
When serotyping a bacteria, what kind of bacterial traits are identified?
.
What is required for a direct immunofluorescence test?
Known antibodies
What is serum titer?
- the concentration of antibodies in a sample
- determined by serially diluting patient serum into test tubes or wells of a microtiter plate
- defined by the highest dilution of serum that still produces agglutination
How is titer related to infection or infectious agent?
.
How does the western blot test work?
- A sample of proteins from a bacterial cell or virus is separated via electrical charge within a gel
- The proteins distributed throughout the gel are transferred and immobilized on a filter
- The filter is incubated with a patient’s serum containing antibody
- If the serum contains antibodies to the microbe, they will bind to the antigens on the filter paper
- A second antibody designed to see the Fc portion of a human antibody as an antigen is applied to the filter paper
- After incubation, sites of specific antigen-antibody binding appear as a pattern of bands that can be compare with positive and negative controls
What does western blot test, test for and when is it used?
- Highly specific and sensitive way to identify or verify the presence of microbial-specific antigens in a patient sample
- used as a verification test for HIV screening tests
What are phenotypic methods of identification?
- Isolation Media
- Differential media
- Blood cultures
- Biochemical Testing
- Miscellaneous Tests
- Phage typing
- Antimicrobial sensitivity tests
What are examples of biochemical tests?
- Carbohydrate fermentation: production of acid and/or gas
- Hydrolysis of gelatin, starch, and other polymers
- Actions of enzymes: catalase, oxidase, coagulase
- Various by-products of metabolism
What are the advantages of genotypic methods of identification?
Get results in 3 hours rather than weeks.
Where is specimen collected?
.
How is specimen collected?
.
What type of media is required for specimen collection?
Isolation media
What is the tuberculosis serological test?
- A small amount of purified protein derivative from Mycobacterium tuberculosis is injected into the skin
- The appearance of a red, raised, thickened lesion indicates exposure to tuberculosis
What is required for antibody testing?
.
What does serological testing rely upon to be effective?
Antibody/antigen
