Immunoassay

Question 1

Heterogeneous immunoassay

Answer 1

Those that require physical separation of bound and unbound reactants

Question 2

Homogeneous immunoassay

Answer 2

Those that require no separation. Homogenous assays are often used in automated instrumentation

Question 3

Immunoassay methods: Heterogeneous
Competitive binding technique

Answer 3

Native and labeled drug compete for sites on a drug specific antibody
Label concentration measured is inversely proportional to the concentration of native drug
Frequently used in drug testing

Question 4

Immunoassay Method: Heterogeneous
Sandwich Technique

Answer 4

Native antigen (drug) reacts with an antibody specific to the drug attached to a solid phase
A second antibody with a tag is attached to the antigen (drug) in the second step
Concentration of drug in patient is directly proportional to the concentration of native drug

Question 5

Immunoassay Method: Heterogeneous
Double Antibody Technique

Answer 5

This technique is not used in drug testing
It is used only for antibody detection
Antibody from patient reacts with a solid phase antigen.
In the second step an antibody with a tag is attached to the native (patient) antibody.
The concentration of tag is directly proportional to the concentration of antibody in the patient’s serum

Question 6

Immunoassay: Homogeneous
Fluorescence Polarization Immunoassay

Answer 6

Bound is distinguished from unbound because the bound particle is heavier and moves more slowly in solution and lines up with a polarizing lens so the light signal from the tag can be detected

Question 7

Immunoassay: Homogeneous
Enzyme Multiplies Immunoassay

Answer 7

Bound is distinguished from unbound because the bound enzyme stops a color change from occuring
In this assay, the amount of tag measured is inversely proportional to the concentration of the drug present in the patient’s serum