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22 Cards in this Set

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What is the basis of an agglutination test?
Not all antibody-antigen complexes precipitate readily, a visible reaction may be obtained if the antibody(or antigen) is attached to something that will agglutinate when the complex reaction occurs(RBC, bacteria or antigen coated beads.
What is flocculation?
This is a variation of agglutination, in which the aggregate is visible but smaller, in suspended fluffy, or colloid form.
List several types of agglutination tests.
1.A/B RBC antigen
2. Heterophil antibody
3. Syphilis test
4. latex agglutination
5. HCG assay for pregnancy
6. Widal test
7. Weil Felix test
8. Cold agglutinin test
9. Coombs test
What is the Heterophil antibody test?
This is a test often used for mononucleosis. These antibodies occur in mononucleosis, and are antibodies that react with a number of diverse antigens.
Agglutination of sheep RBCs by the patients serum suggests the presence of heterophil antibodies and mononucleosis.
The mono spot test is a more rapid acting variation of this test that uses horse RBCs. TRUE/FALSE
How is the syphilis test executed?
In the VDRL screening test, cardiolipin, an antigen released from the treponema organism, is added to samples ofthe patients serum. If microflocculation occurs, the test suggests syphilis, but is not highly specific.
What is the latex agglutination test?
This is employed for rheumatoid factor in rheumatoid arthritis.
Rheumatoid factor is an IgM that is anti-IgG. IgG is bound in the test to tiny latex particles, which agglutinate on adding patients serum that contains rheumatoid factor.
How does the HCG hormone assay test work?
1. It involves agglutination inhibition. It tests for HCG, which is present during pregnancy.
2. Latex particles are first coated with HCG. The patients urine is mixed with with anti-HCG.
3. if the urine contains HCG, it neutralizes the anti-HCG and when added to the latex particles, will not agglutinate them.
4. Thus the absence of agglutination during the test constitutes a positive test for pregnancy.
What is the Widal test?
This test detects antibodies to salmonella when agglutination of salmonella typhosa occurs on the latter's exposure to the patients serum. Similar tests are used for brucellosis and Tularemia.
What is the Weil-felix test?
This is a test for Rickettsial disease. Dilutions of the patients serum are exposed to Proteus OX-19, a bacterium that has antigen in common to rickettsia. Agglutination is consistent with rickettsial disease(also with proteus).
What is the Cold agglutination test?
This tests the special property of red cell antibodies to reversibly agglutinate red cells in Mycoplasma pneumoniae, when the patients serum and RBCs are exposed to cold.
What is the Coomb's test?
This detects antibodies to RBCs and is particularly useful in the diagnosis of hemolytic anemia. In the direct test, antiglobulin is added to the patients red cells. Agglutination points to the presence of the patients antibody on the red cells.
In the indirect Coombs test, which is a test for circulating antibody in the patients serum.
The patients serum is mixed with donor red cells; antiglobulin is then added.
Agglutination will occur if the antibodies from the patients serum had combined with the red cells.
What is anti-streptolysin O titer?
Streptolysin O, a product of streptococci lyses RBCs.Anti-streptolysin O antibodies(ASO) develop during streptococcal infections. ASO in the patients blood can be detected by mixing the patients serum with streptolysin O and human RBCs and noting that hemolysis will be inhibited by the patients serum. It is the streptolysin O that is neutralized in the test.
What is the HA inhibition test?
The influenza virus contains hemagglutinin(HA) which can agglutinate RBCs. This test examines for the presence of anti HA in the patients serum.
How is the HA inhibition test executed?
1. The patients serum is mixed with viruses containing HA.
2. If anti-HA is present, it neutralizes the HA and significant hemagglutination will not occur when RBCs are added.
3. It is the virus that is neutralized in the test.
What is the complement fixation test?
These tests are useful in the detection of a wide variety of viral antibodies.
Hemolysin antibody causes lysis of red cells provided that complement is also present. This lysis can be inhibited in the presence of immune complexes, which combine with complement and thereby prevent complement from facilitating the lysis.
How is this test executed?
1. sheep RBCs are coated with hemolysin and mixed with guinea pig complement, the patients serum, and the viral antigen of interest.
if the patients serum has antibody to the viral antigen, it will combine with the viral antigen, form an immune complex which will neutralize(fix) the complement, and inhibit the hemolysis.
What is ANA titer?
Antibodies to nuclear antigens(ANA) present in patients with SLE and other rheumatic diseases may be detected using a fluorescent marker.
How is ANA executed?
1. The patients serum is applied to a slide containing fixed cells. Any anti nuclear antibodies will bind to the nuclei.
3. After washing away any serum protein that did not bind, an anti-human immunoglobulin antibody labeled with fluorescein is added. This will bind to the patients antibodies.
4. After washing any unbound labeled antibody away, the slide may be examined under a fluorescein microscope.
5. if the patient had ANA, the sandwich of the nuclei, the ANA and the labeled anti-human antibody can be seen because of the fluorescein label.
What is the ELISA test?
Enzyme linked immunosorbent assay.
One coats the wall of a polystyrene microplate well with antigen, say hepatitis B antigen(HBsAg).
2. The patients serum is then applied to the well. if the serum contains anti HBsAg, it will stick to the coated antigen.
3. The antibody can then be detected by applying to the well a second antibody(anti-human IgG) that is labeled with enzyme. The presence of the resulting sandwich can be detected through testing for enzyme activity.
What is the western blooting technique?
An electrophoresis sample is picked up(blotted) from its elecrtophoretic gel onto a membrane that now becomes a duplicate of the electrophoretic pattern.
Specific labeled antibody is then applied to the membrane to test for the presence of specific corresponding antigen. The separation of the antigen from the gel allows the antigen to react better.
what is the practicality of the test?
In testing for antigen or antibody, it is often useful to compare a patients serum sample with known standards.
It may also help to compare the patients serum sample in the acute phase of an illness with a latter phase, because changes in antibody or antigen titers can provide a better idea of the course of the disease, and whether or not existing antibodies are due to an old illness.