How SARS-CoV2 Antigen Rapid Tests work (Covid-19 Testing)

Summary

Antigen rapid tests are essential tools in diagnosing COVID-19, providing results in about 15 minutes. Unlike PCR tests, they use lateral flow technology, similar to pregnancy tests, to detect specific viral proteins. The test works by applying a sample onto a pad where antibodies react with the virus, creating visible lines that indicate a positive or negative result. Three types of antibodies—primary, secondary, and immobilized—are used to bind to viral proteins and display the results. This simple, fast process is crucial for quick detection and public health efforts during the pandemic.

Takeaways

• 😀 Antigen rapid tests are a key tool in detecting COVID-19, providing results in about 15 minutes.
• 😀 These tests typically use lateral flow mechanisms, similar to pregnancy tests, to deliver results quickly.
• 😀 The tests detect a surface protein of the coronavirus to determine whether a person is positive or negative.
• 😀 A visible result is shown through test and control lines: two lines indicate a positive result, while one line signals negative.
• 😀 Antigen rapid tests rely on antibodies, including primary, secondary, and immobilized antibodies for virus detection.
• 😀 Primary antibodies are often labeled with gold particles to bind specifically to the virus’s surface protein.
• 😀 Immobilized antibodies on the test pad capture virus particles as the sample flows across the test area.
• 😀 Secondary antibodies bind to the primary antibodies, forming a visible red line if the test is positive.
• 😀 If no virus is present, no primary antibody binding occurs, resulting in no red test line, only a control line.
• 😀 The flow of the sample through the test pad, driven by capillary action, allows for the detection of viral proteins.
• 😀 The presence of a control line alone signals a negative result, ensuring that the test was performed correctly.

Q & A

What is the main advantage of antigen rapid tests compared to PCR tests?

Antigen rapid tests can provide results in about 15 minutes, whereas PCR tests take longer and require laboratory processing.

How do antigen rapid tests detect the presence of COVID-19?

Antigen rapid tests detect the presence of surface proteins of the coronavirus in a sample, which are identified using antibodies.

What is the basic principle behind how antigen rapid tests work?

Antigen rapid tests use a lateral flow mechanism, where a sample is applied to a test pad, and through capillary flow, it interacts with antibodies that either capture or pass over the test lines, producing a visible result.

What is the purpose of the test and control lines in antigen rapid tests?

The test line signals whether the sample is positive by showing a visible red line, while the control line confirms the test worked properly. A positive result shows both lines, and a negative result shows only the control line.

How do the antibodies in antigen rapid tests function?

The antibodies are used in three variants: primary antibodies that bind the virus, immobilized antibodies on the test pad that capture the virus, and secondary antibodies that detect the primary antibodies, making the result visible.

Why are gold particles used in antigen rapid tests?

Gold particles are used to label the primary antibodies because they provide a clear visual signal (such as a red line) when they bind to viral proteins.

What happens when a sample is negative in an antigen rapid test?

In a negative result, the primary antibodies do not bind to any viral proteins, and only the secondary antibodies bind, showing a signal at the control line but no signal at the test line.

What role does capillary flow play in the antigen rapid test?

Capillary flow allows the sample to move along the test pad, carrying the virus and antibodies to the test and control lines, where reactions can be observed.

What does the appearance of two lines on the antigen test result indicate?

Two lines on the test result—one at the test line and one at the control line—indicate that the sample is positive for COVID-19.

Why is it important to have both primary and secondary antibodies in the test?

Primary antibodies bind to the viral proteins, while secondary antibodies help detect the primary antibodies. Together, they enable the visual confirmation of the test result.