Block B

Question 1

What is the basis of many modern pregnancy tests?

Answer 1

The detection of increased levels of HCG (Human Chorionic Gonadotropin) in blood and urine.

Question 2

What is the A-Z test?

Answer 2

A test where urine was injected into an immature rat or mouse. If the animal showed an estrous reaction (went into heat), the urine was from a pregnant woman.

Question 3

Name three immunoassays used to detect pregnancy.

Answer 3

Inhibition of latex agglutination, radioimmunoassay (RIA), and dip-stick tests.

Question 4

Describe how the inhibition of latex agglutination test works in pregnancy testing.

Answer 4

Rabbit anti-HCG is mixed with the urine sample. If HCG is present, it binds to the anti-HCG. Latex beads coated with HCG are added. No agglutination indicates a positive result (pregnancy) because the anti-HCG is already bound to the HCG in the urine.

Question 5

How does a Radioimmunoassay (RIA) work for pregnancy detection?

Answer 5

Rabbit anti-HCG is mixed with the sample. Radio-labelled HCG is added. If HCG is present in the sample, the radio-labelled HCG cannot bind to the anti-HCG. Low radioactivity is a positive result (pregnancy).

Question 6

Describe how a dip-stick test works to detect pregnancy.

Answer 6

Coloured latex beads coated with anti-HCG are on the dipstick. If HCG is present in the urine, it binds to the anti-HCG on the beads. The beads move up the filter paper and are captured at a line of immobilised anti-HCG, creating a coloured line. A second line appears as a positive control. Two lines indicate a positive result (pregnancy).

Question 7

What are some disadvantages of using animals in pregnancy tests?

Answer 7

Animal use is expensive, unreliable, poses ethical concerns, and is time-consuming.

Question 8

What are the advantages and disadvantages of the inhibition of latex agglutination test?

Answer 8

Disadvantages: It is time consuming, relies on visual interpretation and it’s not quantitative.

Question 9

What are the advantages and disadvantages of the Radioimmunoassay (RIA) test?

Answer 9

Advantages: Can be easily automated and easily quantified. Disadvantages: Produces radioactive waste.

Question 10

What are the advantages and disadvantages of the Dip-stick test?

Answer 10

Advantages: Very simple to use. Disadvantages: Not quantitative.

Question 11

What is a digital pregnancy test?

Answer 11

It uses the same test strip as a regular dipstick test, but a spectrophotometer measures the absorbance of the test area and a computer program calculates the HCG concentration and displays the appropriate message.

Question 12

Name three conditions besides pregnancy where HCG levels might be elevated.

Answer 12

Some tumours, incomplete abortions and the absence of HCG in ectopic pregnancies.

Question 13

What does HIV infect?

Answer 13

CD4+ T cells.

Question 14

How is the progression of HIV infection to AIDS monitored?

Answer 14

By monitoring the decline in the number of CD4+ T cells.

Question 15

What are the main components of a flow cytometer?

Answer 15

A laser beam, forward scatter detector, side scatter detector and fluorescent photon multiplier tubes.

Question 16

What is the principle behind using a flow cytometer?

Answer 16

Cells in suspension are passed through a laser beam, and the light emitted is measured to determine the size, granularity and presence of fluorescent labels.

Question 17

What is measured by the forward scatter and side scatter detectors in a flow cytometer?

Answer 17

Forward scatter: Cell size. Side scatter: Cell granularity and complexity of surface topography.

Question 18

How is flow cytometry used to monitor CD4+ T cell counts?

Answer 18

Fluorescently labelled antibodies against CD3 and CD4 are used to identify and quantify different cell populations.

Question 19

What are some limitations of using fluorescent microscopy to quantify T Helper cells?

Answer 19

It is time consuming, can only count a small number of cells and is dependent on the operator’s interpretation.

Question 20

Name three symptoms of an immediate hypersensitivity reaction.

Answer 20

Sneezing, mucus secretion, itchy and teary eyes, coughing and constriction of airways.

Question 21

Describe the steps of a Passive Cutaneous Anaphylaxis test.

Answer 21

Rats are injected with Evans blue dye intravenously. They then receive a serum sample from the patient intravenously. Different allergens are injected intradermally. A blue area appears at the injection site where mast cell degranulation occurs.

Question 22

What does the RIST assay measure?

Answer 22

The total amount of IgE in a sample.

Question 23

What does the RAST assay measure?

Answer 23

The amount of IgE specific to particular allergens in a sample.

Question 24

What is the advantage of RAST over RIST?

Answer 24

RAST can determine which allergens a person is responding to, whereas RIST only determines if a person has elevated IgE.

Question 25

What is the advantage of using protein and bead arrays for allergy testing?

Answer 25

It enables the testing of hundreds of different antigens on a single platform with fluorescent labels, allowing automation.

Question 26

What is a benefit of using bead arrays?

Answer 26

It is adaptable and can be used as a capture system too.

Question 27

How do antihistamines work?

Answer 27

They block the release or action of histamines.

Question 28

What is Therapeutic Drug Monitoring (TDM)?

Answer 28

Monitoring the level of drug concentrations in a patient's serum to ensure the correct dosage for maximum therapeutic benefit while preventing unwanted side effects.

Question 29

Why is TDM important?

Answer 29

It helps to determine the correct dosage of drugs and ensure patients receive adequate levels of the drug while minimizing toxic effects, as well as overcoming issues of variable patient compliance and unique patient considerations.

Question 30

What is the principle behind a Fluorescence Polarization Immunoassay (FPIA)?

Answer 30

FPIA uses polarized light to excite a fluorescently labeled drug, and measures how much the emitted light remains polarized, which is based on the drug binding to antibodies.

Question 31

How does FPIA work to measure drug concentrations?

Answer 31

If a drug is present in high concentration in a sample, the labelled drug will be free to rotate and lose polarization. If drug is present at low concentration, the labelled drug will remain bound to antibodies and conserve polarization.

Question 32

What are the advantages of using FPIA for TDM?

Answer 32

It is accurate, quick, and easy to measure drug concentrations in serum.