Labeled Immunoassay

Question 1

No separation needed; Enzyme Activity diminished after Ag-Ab complex is formed

No cell washing needed; Less sensitive

Answer 1

Homogenous Assay

Question 2

Separation is needed ; Cell washing (remove free to bound analytes)

Answer 2

Heterogenous assay

Question 3

Used as label since it is Cheap, affordable, readily available

Answer 3

Enzymes

Question 4

Enzymes used in Labeled Immunoassays

Answer 4

Horse Radish Peroxidase (HRP) - most common
Alkaline Phosphatase (ALP)
Glucose Oxidase
B-galactosidase
G6PD

Question 5

Change in absorbance is measured by

Answer 5

Spectrophotometry

Question 6

Labeled antigen competes with patient’s unlabeled antigen

Enzyme Activity is INVERSELY PROPORTIONAL to analyte concentration

Answer 6

Competitive / Direct Immunoassay

Question 7

Secondary antibody does not participate on the initial Ag-Ab complex formation

Enzyme Activity is DIRECTLY PROPORTIONAL to analyte concentration

Answer 7

Noncompetitive / Indirect Immunoassay

Question 8

Antigen captured must have MULTIPLE EPITOPES

Enzyme Activity is DIRECTLY PROPORTIONAL to the Ag concentration

Answer 8

Capture Assay / Sandwich Immunoassay

Question 9

Capture Assay / Sandwich Immunoassay is prone to

Answer 9

Hook Effect

Question 10

Homogenous Assay

Antigen is labeled with Enzyme Tag

Once antibody attaches to the antigenic determinant = active site of enzyme is BLOCKED; LOSS OF ENZYME ACTIVITY

Answer 10

EMIT

Enzyme Multiplied Immunoassay Technique

Question 11

Happens when Ag is present in excess amount.

Unexpected fall in amount of Measured analyte due to the presence of extremely high concentration.

Answer 11

Hook effect

Question 12

Enzymes labels with highest turnover and sensitivity

Answer 12

Horse Radish Peroxidase (HRP)
Alkaline Phosphatase (ALP)

Question 13

Remedy for Hook effect

Answer 13

Serum Dilution
Repeat Test