How pregnancy test kits work (PART II) (FL-Immuno/74)

Summary

This video explains the mechanics of a pregnancy test strip, highlighting the roles of the reaction, test, and control zones. It describes how monoclonal enzyme-conjugated anti-HCG antibodies bind to HCG molecules, leading to color development in the test zone for a positive result. In contrast, a negative result shows only one colored line in the control zone. The process involves capillary action, antibody interactions, and enzyme activation, providing a clear understanding of how pregnancy tests function.

Takeaways

• 😀 The pregnancy test strip has three functional zones: reaction zone, test zone, and control zone.
• 😀 The reaction zone contains monoclonal enzyme-conjugated anti-HCG antibodies that are loosely attached to the strip.
• 😀 The test zone has immobilized polyclonal anti-HCG antibodies and inactive dye molecules.
• 😀 The control zone contains immobilized anti-mouse antibodies that are specific for the reaction zone antibodies.
• 😀 In a positive pregnancy test, the urine sample contains HCG, which binds to the reaction zone antibodies.
• 😀 The reaction zone antibodies travel to the test zone where they form a complex with HCG, leading to color development.
• 😀 Both the test zone and control zone show color development in a positive pregnancy test.
• 😀 In a negative pregnancy test, the urine sample does not contain HCG, so no complex is formed in the test zone.
• 😀 In a negative result, only the control zone develops color, indicating that the test is negative.
• 😀 The enzyme-conjugated antibodies in the reaction zone and test zone play a crucial role in color development based on HCG presence.
• 😀 Capillary action draws the urine sample through the strip, allowing antibodies and urine to move through the zones.

Q & A

What are the three zones in a pregnancy test strip?

The three zones in a pregnancy test strip are the reaction zone, test zone, and control zone.

What is the composition of the reaction zone in a pregnancy test strip?

The reaction zone is composed of monoclonal enzyme-conjugated anti-HCG antibodies, also known as MAOIs, which are loosely attached to the strip.

What is the role of the test zone in the pregnancy test?

The test zone contains immobilized polyclonal anti-HCG antibodies and inactive dye molecules. It binds to the HCG enzyme-conjugated antibody complexes to form a 'sandwich' complex.

How does capillary action contribute to the working of a pregnancy test?

Capillary action helps draw the urine sample up the strip, allowing it to reach the reaction, test, and control zones for the required interactions.

What happens when a pregnancy test detects HCG in the urine sample?

When HCG is present in the urine sample, the enzyme-conjugated antibodies in the reaction zone bind to HCG, and these complexes move to the test zone where the HCG gets 'sandwiched' between the reaction zone and test zone antibodies, leading to color development in both the test and control zones.

What is the significance of the control zone in a pregnancy test?

The control zone contains immobilized anti-mouse antibodies, which bind to the reaction zone antibodies. This results in a colored line in the control zone, confirming that the test is working properly.

What does a positive pregnancy test look like?

A positive pregnancy test shows colored lines in both the test zone and the control zone, indicating the presence of HCG in the urine.

What happens in a negative pregnancy test?

In a negative pregnancy test, there is only one colored line, which appears in the control zone. This happens because there is no HCG in the urine sample to bind to the test zone antibodies.

Why do reaction zone antibodies move along the strip in a negative pregnancy test?

In the absence of HCG, the reaction zone antibodies do not bind to anything and thus move further along the strip by capillary action, passing through the test zone without any interaction.

How is the color development in the test and control zones triggered?

Color development in the test and control zones occurs when the enzyme-conjugated antibodies act on the inactive dye molecules. In the test zone, no color develops if HCG is absent, but the enzyme in the control zone activates the dye, resulting in a colored line.