Chapter 5: Immunoassays

Question 1

Antibodies

Answer 1

Immunoglobulins capable of binding specifically to natural and synthetic antigens

Question 2

Polyclonal antibodies

Answer 2

Derived from different plasma cell lines or clones

Question 3

Monoclonal antibodies

Answer 3

One plasma cell line or clone (more specific)

Question 4

Antigens

Answer 4

Any material capable of reacting with an antibody; does not need to be capable of inducing antibody formation

Question 5

Immunogen

Answer 5

Chemical substance capable of inducing an immune response

Question 6

Haptens

Answer 6

Capable of producing antibodies; can synthesize an antibody specific to itself when conjugated to an immunogenic carrier

Question 7

Immunoassay labels

Answer 7

Used as detectors in immunoassays; chemically bonded to the antigen through a series of chemical reactions

Question 8

Enzyme label

Answer 8

Absorbance spectroscopy method

Question 9

Fluorescein label

Answer 9

Fluorescence method

Question 10

Acridinium esters label

Answer 10

Chemiluminescence method

Question 11

Competitive immunoassay

Answer 11

Measuring unknown antigen in the patient’s sample; begins with the addition of patient sample to a mixture with a known antigen and the corresponding antibody

Patient sample (unknown Ag) + Rgt 1 (known Ag*) + Rgt 2 (known Ab)

More assay signal = less sample analyte (patient concentration)

Question 12

Homogenous immunoassay

Answer 12

No physical separation of the bound and free forms or phases (no wash step)

Question 13

Heterogeneous immunoassay

Answer 13

Physical separation of bound from free forms (wash step to remove unbound Ag/Ab)

Question 14

Noncompetitive sandwich (immunometric assay)

Answer 14

Label is attached to a second antibody; antigen must have two binding sites (epitopes) to complex both antibodies

Patient sample (unknown Ag) + Rgt 1 (known Ab) + Rgt 2 (known Ab*)

More assay signal = more patient concentration

Question 15

Microparticulate enzyme immunoassay (MEIA)

Answer 15

Uses latex microparticles coated with an analyte-specific antibody; second antibody is labeled with ALP; analyte in patient sample binds to both

Question 16

Chemiluminescent enzyme immunoassays (CL-EIA)

Answer 16

Provides methods to measure therapeutic drugs, hormones, and tumor markers; uses a chemiluminescent substrate that can react with an enzyme to produce light

Question 17

Enzyme multiplied immunoassay technique (EMIT)

Answer 17

Developed to screen urine samples for drugs of abuse; now includes therapeutic drugs

Question 18

Substrate-labeled fluorescent immunoassay (SLFIA)

Answer 18

Can be used to measure therapeutic drugs, hormones, and immunoglobulins

Question 19

Fluorescence polarization immunoassay

Answer 19

Uses fluorescein (excites at 490 nm and reemits fluorescence at 520 nm)

Question 20

Chemiluminescent immunoassays (CLIA)

Answer 20

Commonly used label is acridinium ester

Question 21

Electrochemiluminescent immunoassay (ECLIA)

Answer 21

Uses a chemical label that can generate light via an electrochemical reaction

Question 22

Hook effect

Answer 22

As the concentration of analyte begins to exceed the amount of antibody, the dose-response curve will flatten; curve may become negatively sloped with further increases in analyte (hook effect or high-dose hook effect)