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46 Cards in this Set
- Front
- Back
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What is a classic example of agglutination inhibition ?
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pregnancy testing
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What do we look for in the pregnancy test ?
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Human chorionic gonadotropin hormone hCG
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Where does hCG appear ?
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in the serum and the urine (early in pregnancy )
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What is the Gravindex Slide test?
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latex particles coated with hCG used to detect the presence of hCG in the urine
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What 2 steps does Gravindex Slide test involve ?
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1.incubate the patient's urine with anti hCG
2.latex particles with hCG are then added |
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Describe a +ve Gravindex slide test for pregnancy.
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when the patient's urine containing hCG is mixed with anti hCG all the antigens will be neutralized so when the latex particles with the ag on them are added no agglutination is seen since no free antibodies is present
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Describe a -ve Gravindex slide test for pregnancy.
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When a patient 's urine that is -ve for hCG antigen is mixed with anti hCG the antibodies will remain so when the latex particles coated with hCG are added agglutination will occur since antibodies are free indicating a negative result for hCG in urine
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What are the indicator particles in Gravindex Slide test ?
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latex particles coated with hCG
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What are the indicator particles in hemagglutination inhibition ?
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RBCs
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what is hemagglutination inhibition used for?
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to detect antibodies of some viral infections like:
measles mumps rubella influenza |
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What do red blood cells have on their surface that makes the hemagglutination inhibition method possible ?
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receptors for certain viruses.
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What happens in HI when the virus is present with RBCs ?
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spontaneous agglutination occurs with the virus particles linking the RBCs together
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What is seen in the serum of patient that is exposed to a virus ?
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specific antibodies to that virus
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What do the antibodies found in the serum of an infected individual prevent in the body ?
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spontaneous agglutination of the red blood cells
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What causes the agglutination of the RBCs the antibodies of the viruses found in the serum or the viruses themselves ?
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the viruses
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What are the 2 steps procedures of the HI ?
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1. patient's serum is incubated with a known viral antigen
2. Add RBCs that the virus is known to agglutinate |
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Describe a +ve viral infection the using HI testing sequence.
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A patient serum who is +ve infected will have Abs against the infection, when a viral antigen is added a complex will form and neutralize all the Antibodies, when RBCs are added no antigens are present to cause hemagglutination thus no agg will mean a +ve viral infection
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Describe a -ve viral infection using the HI testing sequence.
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A patient whose serum is -ve with Abs for a virus, will not form a complex with the viral antigens when added, thus leaving them free to react with the added RBCs causing Hemagglutination .
So +ve Hemagglutination means a -ve test and -ve viral infection. |
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What is the principle of the neutralization reactions ?
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the ability of the antiserum to neutralize the effect of its corresponding antigen
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What are the antigens in the neutralization reaction ?
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toxins
virus enzyme |
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What are 2 applications to neutralization reactions ?
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Viral neutralization
detection of ASO antibodies |
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What is the indicator in the neutralization reactions ?
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Virus antibody mixture injected into an animal/RBC
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What are the steps of Viral neutralization ?
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a lethal viral dose is mixed with the serum to be tested for a corresponding Ab, then the mixture is injected into a lab animal.
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If the animal dies after the mixture in a VN is injected into him what does that corresponds to ?
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this means that the Ab is not present in the serum and failed to neutralize the lethal dose, hence the virus is -ve in the pt
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If the animal does not die after the mixture in a VN is injected into him what does that corresponds to ?
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this means that the Ab is present in the serum and neutralized the lethal dose, hence the virus is +ve in the pt
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2 other names for Group A strep
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S.pyogenes
Beta hemolytic strep |
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What types of infections are caused by Group A strep ?
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pharyngitis
skin infections rheumatic fever glomerulonephritis |
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In what stages of diagnosis of Group A strep does serology play a role ? why ?
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in stages where symptoms vary between rheumatic fever and glomerulonephritis
organism at that time may be absent in the pharynx and skin only 25% have positive cultures at that time |
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How many exotoxins does Group A strep produce and what is the most important one ?
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20 different exotoxins and the most important one is Streptolysin O.
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What does Streptolysin O act like ?
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a stimulating Ag that causes the secretion of antistreptolysin antibody.
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describe a +ve test for streptolysin O .
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patients serum with +ve antistreptolysin O is mixed with streptomycin O, the Abs are neutralized, then RBCs are added, no hemolysis is seen since the Ag is neutralized by the Abs of the Pt.
No hemolysis --> +ve test |
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Describe a -ve test for streptolysin O.
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patients with serum -ve for antistreptolysin O is mixed with SO antigens, no neutralization occurs so when RBCs are added, hemolysis occurs since Ags are still there
Hemolysis ---> -ve test |
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What is a titer for ASO ?
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highest dilution giving no hemolysis
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in what units is the titer of ASO given ?
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Todd units
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What does the normal range of ASO titer depend on ?
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pt age
season of the year(winter and spring have higher titers |
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How many phase diagnosis for ASO is ideal for diagnosis ?
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2
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What is the cut off of ASO titers ?
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200 units
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What does titers above 200 and 300 todd units indicate ?
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>200 abnormal
>300 rheumatic fever or acute glomerulonephritis |
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IS the sensitivity high for the commercial slide agglutination tests for streptococcus A ?
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no
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what is the complement fixation test useful for ?
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the detection and quantitation of Abs
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What happens in the CF test after the formation of an Ag Ab complex is formed ?
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fixes the compliment and activates the compliment system
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What are the 2 steps of the CF ?
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test system
indicator system` |
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Describe the steps of a +ve test
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known antigen is reacted with the Pt serum containing Ab to form a complex, this serum is treated at 56 deg for 30 minutes to destroy C then add guinea pig serum add SRBC with AntiSRBC hemolysin and incubate (also pre treated) no hemolysis is seen.
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Describe the steps of a -ve test
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Antigen is reacted with serum that does not have the Ab present then Guinea pig C protein is added, SRBC and Anti SRBC are then added, since no antigen to neutralize the C protein and antigen , they will bing to the RBC and the complement system will be activated causing hemolysis
Hemolysis---> -ve test |
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What is the clinical application of the CF test ?
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viral,bacterial,parasitic infection. WEinberg test for hydatid disease
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What are the advantages of the CF method and the disadvantages ?
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the test is specific and sensitive but time consuming
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