Serology And Rapid Tests

Question 1

Explain the significance of the viral window.

Answer 1

Time gap between exposure to antigen and the response kicking in

Question 2

Interpret an acute and convalescent EIA bacterial/viral titer.

Recognize the significance of IgM, IgG, and acute vs. convalescent titer deltas.

Answer 2

Acute: IgM (current or recent infection)
Convalescent: IgG (past infection)

*There is a “greater than or equal to” 4-fold increase between acute and convalescent serum titers

Question 3

Define the term ELISA.

Identify the type of protein targeted by a direct and indirect ELISA.

Answer 3

ELISA = Enzyme-Linked ImmunoSorbant Assay

• Direct targets Antigen (hormone, enzyme, microbial antigen, drug)
• Indirect targets Antibody (infectious agent exposure, HIV)

Question 4

Outline the key components and steps involved in performing an indirect ELISA.

Interpret data generated from an indirect ELISA.

Answer 4

• Probes for ANTIBODIES to an antigen…labeled antibody binds to an unlabeled antibody**
• Unlabeled “primary” antibody
• Reporter enzyme labeled antibody
• Colorless substrate

Question 5

Identify the purpose of performing a direct fluorescent antibody (DFA) test vs. an indirect fluorescent antibody (IFA) test

Answer 5

DFA: lights up specific cells or microorganisms

IFA: demonstrates the presence of antibodies against a specific antigen

Question 6

Explain the similarities between direct ELISA/DFA and indirect ELISA/IFA.

Answer 6

Direct: Identify the ANTIGEN

Indirect: Identify ANTIBODIES to the antigen

Question 7

Interpret a precipitin curve - explain the significance of prozone, equivalence zone, and antigen excess zone in determining a positive agglutination test.

Answer 7

Prozone: Antibody excess; high levels of free antibody saturate antigens, but very little cross-linked Ag:Ab complexes (Example ratio would be 1:2)
Low point on bell curve

Equivalence Zone: no free Ag of Ab remains in solution after centrifugal ion — MAXIMAL PRECIPITATION (Example ratio would be 1:16)
Peak on bell curve

Antigen Excess Zone: high levels of free antigen in solution after formation of Ag:Ab complexes; produce very little cross-linked Ag:Ab complexes (Example ratio would be 1:128)
Low point on bell curve