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CLINICAL CHEM > Immunoassays > Flashcards

Immunoassays Flashcards

(100 cards)

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1
Q

who proposed that antigen combined with pre-existing side-chains on cell surfaces.

A

ehrlich

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2
Q

what is the basis of immunoassays

A

specific binding between Ag and corresponding Ab

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3
Q

what kind of bond is Ab-ag

A

non covalent

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4
Q

is the binding of Ab and Ag reversible

A

yes

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5
Q

def? the initial force of attraction that exists between a single Fab site on an antibody molecule and a single epitope site on the corresponding antigen

A

affinity

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6
Q

def? the overall strength of antigen-antibody binding and is the sum of the affinities of all the individual antibody-antigen combining sites.

A

avidity

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7
Q

what is cross reactivity

A

ab reacting with ag that is structurally similar to the homologous ag

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8
Q

what kind of immunochemical method is precipitation and light scattering

A

direct

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9
Q

what kind of immunochemical method is label methods

A

indirect

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10
Q

what immunoassays fall under the precipitation category

A

immunodiffusion and immunoelectrophoresis

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11
Q

what immunoassays fall under the light scattering category

A

nephelometry and turbidimetry

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12
Q

what immunoassays fall under the label method category

A

non competitive, competitive, heterogeneous, homogeneous

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13
Q

Immunoassays that detect antigen-antibody complex formation directly without labels are known as _____ or _______ immunoassays

A

direct; non labeled

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14
Q

is a label involved in precipitation immunoassays

A

no

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15
Q

are precipitation assays qualitative or quantitative

A

both

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16
Q

major components of direct assays

A

solution, gel, instrument

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17
Q

where are ag and ab in a direct immunoassay

A

diffusing into the solution

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18
Q

what factors affect solubility

A

size, charge, temp, and solvent ionic strength

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19
Q

describe the prozone

A

ab is in excess

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20
Q

describe the zone of equivalence

A

ab and ag are equal

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21
Q

describe the postzone

A

ag is in excess

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22
Q

does precipitate form in the prozone and postzone

A

no

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23
Q

A patient’s sample contains equal amount of Ab and Ag, but the reaction in a test system containing antigen is negative (no ppt). What has happened?

A

low specificity

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24
Q

t or f: Precipitation reactions in gel are not commonly performed in the clinical laboratory today

A

T

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25
what is gel made out of
dilute agarose
26
what kind of buffer is used for gel electrophoresis precipitation
aqueous
27
what kind of medium is gel considered
semisolid
28
what kind of assay do immune complexes separate more easily
gel
29
in double diffusion radial immunodiffusion does the Ab or Ag diffuse into the gel
both
30
where is the Ag placed in double radial immunodiffusion
center well
31
where is the Ab placed in double radial immunodiffusion
in the wells surrounding the center well
32
what kind of diffusion technique is radial immunodiffusion
double diffusion and single
33
is double radial immunodiffusion qualitative or quantitative
qualitative
34
what does single radial immunodiffusion quantitatively determine
Ag
35
where is the Ab in single radial immunodiffusion
incorporated into liquefied agar
36
where is the Ag in single radial immunodiffusion
well
37
how is the amount of Ag quantified in radial immunodiffusion
by the amount of diffusion
38
how is the amount of Ag quantified in single radial immunodiffusion
diameter of ppt ring
39
what math equation can you use to determine conc of Ag in single radial diffusion
standard curve
40
what are the Y and X axis of the standard curve
Y axis: diameter of the ring X axis: conc of Ag
41
Which part of the double immunodiffusion (RID) test system contains the antisera?
outer well
42
Which part of the single immunodiffusion (RID) test system contains the antisera?
gel
43
Why would we want to combine immunodiffusion with electrophoresis? (electroimmunodiffusion)
speed and specificity
44
what kind of diffusion technique is electroimmunodiffusion
single electro-immunodiffusion technique
45
where is the Ab located in electroimmunodiffusion
in gel
46
T or F: the pH of the electroimmunodiffusion gel is at a pH that immobilizes the Ab
T
47
where is the Ag located in electroimmunodiffusion
wells
48
what moves negatively charged antigens into the agar in electroimmunodiffusion
electric current
49
what can happen if an electroimmunodiffusion gel is read during the initial phase and why
no ppt because there is excess Ag; the more the Ag migrate the more Ab they encounter
50
do Ag migrate towards the anode or cathode in electroimmunodiffusion
anode
51
what shape ppt forms in electroimmunodiffusion
rocket shaped
52
what is proportional to the amount of Ag conc in electroimmunodiffusion
area under rocket shaped ppt
53
what part of immunoelectrophoresis provides separation
Electrophoresis
54
what part of immunoelectrophoresis provides detection
Immunoprecipitation
55
what is the main advantages of immunoelectrophoresis
the number of antigens can be identified in serum and more specific
56
what test would you use to find the identification and approximate quantization of various proteins present in the serum
immunoelectrophesis
57
Immunoelectrophoresis is used in patients with suspected _______ and ________ gammopathies.
monoclonal and polyclonal
58
what are the 2 phases of immuno electrophoresis
electrophoresis and fixation
59
what is applied to the serum in immunofixation electrophoresis
serum
60
do the serum proteins in immunofixation electrophoresis move towards the anode or cathode
cathode
61
what is inoculated with the serum proteins in immunofixation electrophoresis
antiserum
62
what is present if ppt forms in the fixation phase of immunization electrophoresis
Monoclonal proteins
63
what is done to the gel after ppt forms
washed, stained, destained, and dried
64
when would you use immunofixation electrophoresis in a clinical setting
identify abnormal bands seen on serum or urine protein electrophoresis
65
what does immunofixation electrophoresis determine
type of Ab/immunoglobulin present
66
what is an example of immunization electrophoresis
western blot
67
what Two analytical methods are based on light scattering
Turbidity and nephroticelometery
68
how is Ag conc determined using immunoturbidimetric assay
sample absorbance is compared to known Ag conc absorbance
69
what do immuno complex cause to change in immunoturbidimetric assay
absorbance
70
what does the angle of scattered light tell you
size of the immuno complexes and the wavelength of the incoming light 
71
what is a disadvantage of immunoturbidimetric assay
analytical device can be a source of errors
72
what is measured in nephelometry
scattered light
73
what is measured in turbidimetry
transmitted light
74
in nephelometry what angle is scattered light measured at
90
75
in turbidimetry what angle is transmitted light measured at
180
76
what is the detector in nephelometry
PMT
77
what is the detector in turbidimetry
photocell
78
what do indirect/labeled immunoassays detect
labels attached to reactants
79
advantages of radioisotopes
Flexibility Sensitivity Size
80
disadvantages of radioisotopes
Toxicity Shelf life Disposal costs
81
advantages of enzyme labels
Diversity Amplification Versatility
82
Disadvantages of enzyme labels
Lability Size Heterogeneity
83
advantages of florescent labels
Size Specificity Sensitivity
84
Disadvantages of florescent labels
Hardware Limited selection Background
85
an assay that combine chemiluminescence technique with immunochemical reactions
Chemiluminescence immunoassay
86
what kind of labels does Chemiluminescence immunoassay
luminescent
87
in a competitive immunoassay how much labeled ag is added
small amount
88
how much pt ag is in a competitive immunoassay
lots
89
the competitive ELISA relies on the competition between antigen of _____ and ______ antigen towards the _____ amount of antibodies. 
interest, reference, limited
90
what does noncompetitive immunoassays use excess of
ab
91
in noncompetitive immunoassays the Concentration of antigen is directly proportional to
bound labeled ab
92
what kind of ELISA is best for measuring low amounts of Ag
competive
93
what kind of ELISA does not depend on the number of antigens present in a sample
noncompetitive
94
what kind of assay requires a separation step and will produce an inverse relationship between the signal and analyte concentration
competitive heterogeneous immunoassay
95
A noncompetitive heterogeneous immunoassay uses
Excess reagent and requires a separation step
96
Ag∙Ab∙Ab* sandwich assay measures
Ab
97
Ab∙Ag∙Ab* sandwich assay measures
Ag
98
A laboratory is evaluating an enzyme-linked immuno sorbent assay (ELISA) for detection an antibody to cyclic citrullinated peptide (CCP), which is a marker for rheumatoid arthritis. The laboratory includes serum from healthy volunteers and patients with other connective tissue diseases in the evaluation. These specimens determine which factor of the assay:
Specificity
99
What comprises the indicators system in an ELISA for detecting antibody?
Enzyme-conjugated antibody+chromogenic substrate
100
What outcome results from improper washing of a tube or well after adding the enzyme-antibody conjugate in an ELISA system?
Result will be falsely increased

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