Serology Exam 1

Where does complement attach to the immunoglobulin molecule?

Fc region

What role does complement play in the immune response?

group of proteins that work together to eliminate pathogens

Last steps in complement activation result in the formation of _____

membrane attack complex (MAC)

How is complement on a patient’s sample inactivated?

heating the serum for 30 minutes at 56°C.

What is a monoclonal antibody?

An identical antibody produced from one B-cell clone that binds to one specific epitope.

How are monoclonal antibodies made?

fusing antibody-producing B cells with myeloma cells to form hybridomas that produce identical antibodies.

Why are monoclonal antibodies important?

They are identical copies of a single antibody that bind to one specific target antigen, making them exceptionally precise for medical treatments, lab testing, and disease detection

What is seroconversion?

the time when the body starts producing enough specific antibodies to a pathogen (like HIV) so that they become detectable in a blood test after an infection or vaccination

What is an antibody titer and what is considered a diagnostic increase in titer?

type of blood test that determines the presence and level (titer) of antibodies in the blood.

A four fold increase in titer is considered diagnostic of a recent infection

When should the convalescent specimen be drawn for serological testing?

2 to 4 wks

In serological testing what is meant by the “window period”

The period between exposure to the antigen, a development of detectable antibody, if serological testing is done during this period, a false negative reaction will occur

When an antibody is present in the blood of a newborn, how can one determine if it is
passively acquired maternal antibody or antibody produced by the baby?

Check the antibody class: IgG can be passively acquired from the mother, while IgM indicates the baby produced the antibody because maternal IgM does not cross the placenta.

Which antibody class may require the use of an enhancement technique to visualize the
reaction in the lab?

IgG

What is a hapten?

small molecule that cannot cause an immune response by itself (immunogenic) but can when attached to a larger carrier protein.

Active vs passive immunity

Active = you make it. Passive = you receive it.

What is the difference between quality control and quality assurance?

Quality control (QC): Checks that test results are accurate and reliable and helps prevent defects/errors

Quality assurance (QA): Monitors the entire testing process to ensure overall laboratory quality.

List and give examples of the three phases of quality assurance.

1. The Preanalytical phase: test ordering by clinicians , patient preparation/identification, specimen collection, transport, processing.
2. The analytical phase: test analysis, quality control, reagents, calibration, preventive maintenance.
3. Post-analytical phase: verification of calculations and reference ranges, review/reporting of results, procedures for notification of critical values, test interpretation by physician, follow-up patient care.

In which phase of testing do most errors occur?

preanalytical phase

Define Positive predictive value

the likelihood that someone who tests positive actually has the disease

Define Negative predictive value

likelihood that someone who tests negative does NOT have the disease

Define Analytical sensitivity

the ability of a test to detect small amounts of a substance being measured.

Define Clinical/diagnostic sensitiv-ity (sensitivity)

The ability of a test to correctly identify individuals with a disease

Define Analytical specificity

the ability of a test to measure only the intended substance without interference from other substances.

Define Clinical/diagnostic specific-ity (specificity)

the ability of a test to correctly identify individuals who do not have a specific disease or condition

Define Accuracy

how close a measurement is to the true value of the quantity that was measured

Define Precision

measure of how close a series of measurements are to one another, irrespective of the actual value

Define Solute, solvent, solution

Salt = solute | Water = solvent | Saltwater = solution

Solute: The substance being dissolved.
Solvent: The substance that does the dissolving.
Solution: The mixture of the solute and solvent

Define Cross reactivity

an antibody reacts with an antigen other than its intended target because the antigens are similar.

According to CAP how often must quality control statistics be calculated

Monthly

What is the name of a sample which is chemically and physically similar to the unknown?

Which is tested in the same manner as the unknown to monitor the precision of the test system?

Control

For quantitative tests, at least 2 levels of control should be run at least once each day of patient testing. For quantitative tests, a positive and negative should be included with each run of patient specimens.

Who should run controls?

Personnel who routinely perform patient testing.

When should results of control be verified for acceptability?

Before patient results are reported

Which part of a quality management program involves the use of external controls?

Analytical

Define an Antigen

Any substance (typically a large protein or polysaccharide) that triggers an immune response and is capable of binding specifically to antibodies

What is a Epitope?

The specific part of an antigen where an antibody binds.

What is antibody?

A protein made by B cells/plasma cells that specifically binds to an antigen.

What is affinity?

The strength of binding between one antibody binding site and one epitope.

What is Avidity?

The overall strength of all antibody-antigen bonds together.

What is direct agglutination?

Antibodies directly cause naturally occurring particles or cells to clump together.

What is passive agglutination?

Soluble antigens are attached to particles (such as latex beads) to detect antibodies.

What is agglutination inhibition?

No clumping = positive result because the substance being tested prevents agglutination.

What is reverse passive agglutination?

Antibodies are attached to particles to detect antigens.

What is Hemagglutination?

Clumping of red blood cells caused by antibodies.

What is Hemagglutination inhibition?

Prevention of RBC clumping, often used to detect antibodies that block hemagglutination.

Compare precipitation vs agglutination

precipitation involves a soluble antigen that turns into an insoluble complex, while agglutination involves a particulate or cell-bound antigen that forms visible clumps

Compare nephelometry and turbidimetry

In nephelometry the intensity of the scattered light is measured, while, in turbidimetry, the intensity of light transmitted through the sample is measured.

Compare Ouchterlony vs Radial immunodiffusion

Radial Immunodiffusion measures the size of a precipitation zone as for Ouchterlony demonstrates lattive formation in gel

Ouchterlony= Qualitative

Radial Immunodiffusion= Quantitative

REMEBER

Precipitation Curve

Define

Identical

Define

Partially Identical

Define

Non-Identical

What are some sources of error in the ouchterlony/radial immunodiffusion technique

procedural mistakes during well preparation, improper incubation conditions, and measurement inaccuracies

What type of antibodies can cause false positive reactions in hemagglutination tests?

Heterophile antibodies

What must be present in the serum for tests based on hemolysis of RBCs?

Complement must be present in the serum for tests based on hemolysis of red blood cells (RBCs).

Which is more sensitive precipitation or agglutination?

Agglutination

What happens if you rotate your agglutination card for more than the recommended time?

Can cause drying and create of false postitve

Rank the following methods in order of lowest to highest sensitivity (Agglutination,
Precipitation, Immunoassay)

Precipitation, agglutination, immunoassay.

Compare labeled and unlabeled immunoassays

differ primarily by the inclusion of a tracer molecule to detect antigen-antibody reactions

Compare competitive vs non competitive, homogeneous vs heterogeneous, which is most
sensitive?

• Competitive: Patient antigen competes for binding → more antigen = less signal.

• Noncompetitive (sandwich): Antigen is sandwiched between antibodies → more antigen = more signal.

• Homogeneous: No wash/separation step required.

• Heterogeneous: Wash/separation step required.

Most sensitive: Noncompetitive heterogeneous immunoassay.

In a competitive immunoassay, is the amount of signal inversely or directly proportional to the amount of patient's antibody?

Inversely

In a non-competitive immunoassay, is the amount of signal inversely or directly proportional to the amount of patient's antibody?

Directly

What step is required in a heterogeneous immunoassay that is not required in a homogeneous immunoassay?

Separation (washing) step

Sources of error in ELISA testing

incorrect sample dilution, pipetting errors, not washing the wells thoroughly, using expired reagents, and not adhering to the incubation times and temperatures.

First types of immunoassays used what label?

radioactive isotopes (Radioimmunoassay)

Why are enzyme immunoassays (EIA) replacing most radioimmunoassays?

no radioactive hazardous waste

What enzyme labels are commonly used in EIA procedures?

horseradish peroxidase (HRP) and alkaline phosphatase (AP)

What is measured in enzyme immunoassays?

specific antigens or antibody reactions in a patient sample

What can cause a false positive result in enzyme immunoassays?

Inadequate washing can cause a false positive because unbound enzyme-labeled antibodies remain behind, producing color even when the target is not present.

Bands in serum protein electrophoresis, which band travels farthest toward the anode?

Albumin

What band do antibodies migrate to in serum protein electrophoresis?

Gamma

What is Immunofixation Electrophoresis (IFE) useful for?

detection, identification, and characterization of monoclonal immunoglobulins (M-protein)

Define

Monoclonal Gammopathy

Define

Polyclonal Gammopathy

What type of immunoassay would be best used for point-of-care?

Lateral flow immunoassay (LFIA)

What additional quality control is required for tests with built-in controls?

External positive and negative controls

Which methods are most often used on automated immunoassay analyzers?

Chemiluminescence and fluorescence immunoassays

What is Chemiluminescence?

refers to the emission of light (electromagnetic radiation) during a chemical reaction, distinct from heat production.

Name a disease that can cause false-positive results in latex agglutination tests because
of an antibody in the serum that reacts with IgG?

Rheumatoid arthritis