Serological Tests Flashcards

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1
Q

Where are Antibodies and Antigens found?

A

Ab in serum
Ag in serum, body fluids, tissues

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2
Q

Define Test Specificity and Sensitivity

A

Specificity: true negative
Sensitivity: true positive

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3
Q

What is the Lattice formation?

A

Ab-Ag complex

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4
Q

Define Titer

A

The highest dilution of serum which gives an oservable reaction with Antigen

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5
Q

Specificity and sensitivity are directly related with ?

A

Affinity and avidity of the antibody

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6
Q

When does cross reactivity occur?

A

When two or more antigens share similar structural festures -> can have a bad influence on the test sensitivity and specificity

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7
Q

Types of serological testing

A

Type I: performed to detect antigen or antibody, soluble Ag and Ab is used

Type II: immunoassay test, performed within a solid phase, tests based on formation of Ag-Ab complex, identification of Ab isotypes

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8
Q

Where can agglutination tests be performed?

A

On slides, tubes or microtiter plates

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9
Q

Examples of direct agglutination tests

A
  • hemagglutination/ Bacteria
  • WRIGHT for brucellosis
  • Gruber Widal for Salmonellosis
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10
Q

Indirect agglutination

A

Particles artificially covered with Ag
- RBS, polystyrene, latex, charcoal

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11
Q

Explain Coombs test

A

Direct coombs test performed with baby RBCs to detect Ab coating -> antihuman Ab used

Indirect coombs test performed with mothers serum to detect anti Rh Ab

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12
Q

Latex agglutination tests used for identification of which microorganisms?

A

H. Influenza, S. pneumonia, N. Meningitidis, S. aureus, C. Neoformans, C. Albicans, rubella virus

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13
Q

Explain precipitation

A

Ab can combine with soluble ag to form a visible precipitate
-> performed in splutions or in semisolid (agar) medium

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14
Q

Define turbidimetry

A

Measures turbidity by measuring the amount of light directly passing

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15
Q

Define nephelometry

A

Indirect measurment

Measures the scattered light

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16
Q

Neutralisation test principle

A

Serum is mixed with a known viral suspension -> if ab present in serum, they bind to the virus and prevent attachment -> when virus is added to cell culture -> can not replicate & cause cell death

17
Q

Explain the ASO test

A

GAS produce Streptolysin O toxin which hemolyses RBCs
If there is an infection, -> Anti-streptolysin O Ab formation

RBC + Serum -> if there is no hemolysis, this means that the antibodies neutralized the toxin -> INFECTION

18
Q

Explain Ag detection with ELISA Test

A

Ag specific Ab coated well -> add specimen -> wash to remove unbound components -> add enzyme conjugated secondary Ab -> wash -> add substrate

19
Q

Explain Ab detection with ELISA Test

A

Ag coated well -> add Specimen -> wash -> add enzyme conjugated secondary Ab (bind to Fc) -> wash -> Substrate

20
Q

Explain lateral flow assay

A

Sample containing Ag on ped -> Ag goes with capillary flow -> binds particle conjugated Ag specific Ab -> conjugated Ab based Ag captured by secondary Ag (test line) -> other particle conjugated Ab captured by Anti ab (control line)