Precipitation and Agglutination

Question 1

Measure of turbidity or cloudiness in a solution

Answer 1

Turbidimetry.

Question 2

Principle of turbidimetry

Answer 2

Measures reduction in light intensity due to reflection, absorption, or scatter.

Question 3

Unit of measurement in turbidimetry

Answer 3

Absorbance unit; ratio of incident light to transmitted light.

Question 4

Principle of nephelometry

Answer 4

Measures light scattered at a specific angle.

Question 5

Information derived from light scattering in nephelometry

Answer 5

Indicates solution’s concentration.

Question 6

Concentration units in nephelometry

Answer 6

Milligrams per deciliter (mg/dL) or international units per milliliter (IU/mL).

Question 7

Type of precipitation in a solid medium

Answer 7

Immunodiffusion.

Question 8

Advantage of passive immunodiffusion

Answer 8

No electrical current, cheap, simple.

Question 9

Disadvantage of passive immunodiffusion

Answer 9

Longer turnaround time (TAT).

Question 10

Factors affecting rate of diffusion in immunodiffusion

Answer 10

Particle size, temperature, gel viscosity, hydration.

Question 11

End product of Single Diffusion, Single Dimension (Oudin Test)- semiquantitative

Answer 11

Precipitin line.

Question 12

Interpretation of line thickness in Single Diffusion, Single Dimension

Answer 12

Thicker line indicates higher antigen concentration.

Question 13

Result of Single Diffusion, Double Dimension (Radial Immunodiffusion)

Answer 13

Precipitin ring.

Question 14

Relationship between diameter and concentration in Radial Immunodiffusion

Answer 14

Diameter is directly proportional to concentration.

Question 15

Method used in Radial Immunodiffusion for quantitative measurement

Answer 15

Fahey and McKelvey method (Kinetic Diffusion).

Question 16

Time and measurement principle in Fahey and McKelvey method

Answer 16

19 hrs; diameter is proportional to log concentration.

Question 17

Method used in Radial Immunodiffusion for end-point measurement

Answer 17

Mancini method.

Question 18

Time for IgG and IgM in Mancini method

Answer 18

IgG = 24 hrs, IgM = 50-72 hrs.

Question 19

Classification of diffusion in Double Diffusion, Double Dimension

Answer 19

Qualitative.

Question 20

Diffusion directions in Double Diffusion, Double Dimension

Answer 20

Both horizontal and vertical through semisolid medium.

Question 21

Result of identical epitopes in Double Diffusion, Double Dimension

Answer 21

Arc formation (serological identity).

Question 22

Result of non-identical epitopes in Double Diffusion, Double Dimension

Answer 22

Crossed lines (non-identity).

Question 23

Key characteristic of antigen in passive immunodiffusion

Answer 23

Soluble.

Question 24

Technique used to separate molecules using electrical current

Answer 24

Electrophoresis.

Question 25

Effect of direct current in electrophoresis

Answer 25

Forces antigen, antibody, or both to migrate.

Question 26

Result of antigen-antibody migration in electrophoresis

Answer 26

Distinct precipitin bands form.

Question 27

Disadvantage of electrophoresis

Answer 27

Expensive and complex.

Question 28

Type of electrophoresis in Rocket electrophoresis (Laurell Technique)

Answer 28

One-dimensional electroimmunodiffusion.

Question 29

Combination technique used in Rocket electrophoresis

Answer 29

RID + electrophoresis.

Question 30

Relationship between antigen migration and concentration in Rocket electrophoresis

Answer 30

Distance of migration and precipitation is directly proportional to antigen concentration.

Question 31

Interpretation of distance in Rocket electrophoresis

Answer 31

Distance from the starting well to the front of the rocket-shaped arc correlates with antigen concentration.

Question 32

Procedure in Immunoelectrophoresis (IEP)

Answer 32

Double diffusion + electrophoresis.

Question 33

Procedure in IEP for separating proteins

Answer 33

Serum electrophoresed, and a trough is cut parallel to the separation line.

Question 34

Disadvantage of Immunoelectrophoresis (IEP)

Answer 34

Difficult interpretation.

Question 35

Difference between Immunofixation Electrophoresis and IEP

Answer 35

Immunofixation Electrophoresis: applied directly to the gel surface: quicker immunodiffusion and higher resolution.

Question 36

Use of Immunofixation Electrophoresis

Answer 36

Identify and characterize serum/urine proteins.

Question 37

Key feature of Immunofixation Electrophoresis

Answer 37

Highly sensitive and specific; identifies monoclonal proteins.

Question 38

Effect of hypogammaglobulinemias in Immunofixation Electrophoresis

Answer 38

Faintly staining bands.

Question 39

Effect of polyclonal hypergammaglobulinemias in Immunofixation Electrophoresis

Answer 39

Darkly staining bands in the gamma region.

Question 40

Result of monoclonal antibody presence in Immunofixation Electrophoresis

Answer 40

Dark, **narrow bands** in a specific lane.

Question 41

Type of test in Counter Immunoelectrophoresis (CIE)

Answer 41

Qualitative.

Question 42

Procedure in Counter Immunoelectrophoresis (CIE)

Answer 42

Ag and Ab are placed in wells opposite each other; Ag migrates to anode, Ab to cathode.

Question 43

Result of Ag-Ab interaction in CIE

Answer 43

Precipitin line forms where Ag and Ab meet.

Question 44

Use of Counter Immunoelectrophoresis (CIE)

Answer 44

Detect bacterial Ags in fluids for rapid response.

Question 45

Year when Gruber and Durham described agglutination reactions

Answer 45

1896

Question 46

*Particulate antigen aggregates to form larger complexes* in the presence of specific antibody.

Answer 46

agglutination

Question 47

Term for antibodies that cause agglutination

Answer 47

Agglutinins.

Question 48

Two steps in agglutination reactions

Answer 48

Sensitization (no clumping) and lattice formation (visible agglutination).

Question 49

Type of agglutination where antigens are naturally present on particles

Answer 49

Direct agglutination.

Question 50

Examples of direct agglutination tests

Answer 50

Blood typing, Kauffman and White serotyping, Widal test, Weil-Felix, Cold agglutinin test.

Question 51

Process where **soluble antibody (agglutinin)** forms a **lattice** with an *insoluble particulate or cellular* antigen.

Answer 51

Agglutination

Question 52

Reaction where **soluble antigen** combines with **soluble antibody** to produce visible insoluble complexes.

Answer 52

Precipitation

Question 53

A technique where **antigen is attached to a particulate carrier, detecting antibodies** to viruses such as rotavirus, rubella, HBV, HIV.

Answer 53

Passive Agglutination

Question 54

A technique where **antibodies are attached to particulate carriers with active sites facing outward**, used to detect pathogens like Group B Streptococcus.

Answer 54

Reverse Passive Agglutination

Question 55

A process where antibodies are bound to a particle (e.g., bacterium) to enhance the visibility of agglutination.

Answer 55

Co-agglutination

Question 56

A test where the absence of agglutination indicates a positive reaction, used to detect secretor status and viral antibodies.

Answer 56

Agglutination Inhibition

Question 57

A technique that measures non-agglutinating particles by counting them with an optical particle counter, applied in Nephelometry.

Answer 57

Particle-Counting Immunoassay (PACIA)

Question 58

A **specific type of precipitation** that occurs over a **narrow range of antigen** concentrations and involves **fine particles clumping together in a positive reaction**.

Answer 58

Flocculation

Question 59

Examples of tests using flocculation.

Answer 59

Nontreponemal tests: VDRL and RPR.

Question 60

A test measuring the ability of a patient's antibody to neutralize infectivity and protect cells from infection.

Answer 60

Neutralization

Question 61

Types of neutralization tests.

Answer 61

Toxin Neutralization (Schick test, Dick Test, ASO Titration) and Virus Neutralization.

Question 62

Characteristic of precipitation and agglutination assays.

Answer 62

Unlabelled assays; no marker label is needed to detect the reaction.

Question 63

Limitation of precipitation and agglutination assays.

Answer 63

Relatively insensitive, requiring high antigen concentration to visualize the reaction.