In recent years, almost everyone has heard of an antigen test – mainly because of the coronavirus pandemic. But what exactly is an antigen test, how does it work and why is it so useful in laboratory medicine?

What is an antigen test?

An antigen test looks for certain proteins – known as antigens – that are typical of a pathogen such as a virus or bacterium. In contrast to tests that detect antibodies or the DNA of a pathogen, the antigen test is aimed directly at the “fingerprints” of the intruder. It is often carried out with a swab – for example from the throat or nose – and sometimes also with blood or other samples. The result is usually obtained within minutes to hours, which makes it significantly faster than many other laboratory tests.

How does the antigen test work?

The antigen test is like a detector that is programmed to a specific signal. This is how it works:

1. Take a sample: A sample is taken with a cotton swab, for example from the nasopharynx.
   
2. Application: The sample is mixed with a liquid and placed on a test strip – similar to a pregnancy test.
   
3. Reaction: Antibodies are waiting in the test strip that are specifically “tuned” to the antigen being sought. If the antigen is present, it binds to these antibodies.
   
4. Result: A chemical reaction produces a visible line or another signal. One line usually means “negative”, two lines “positive” – depending on the test.

The whole process often only takes 15 to 30 minutes. There are also professional antigen tests for the laboratory that are somewhat more accurate, but the principle remains the same.

What is the antigen test used for?

Antigen tests are mainly used when things need to be done quickly. Their main task is to detect acute infections. Examples:

• Corona: Rapid tests for SARS-CoV-2 were in use everywhere during the pandemic – in schools, companies and at home.
  
• Influenza: They help to distinguish flu viruses from other colds.
  
• Streptococci: If you have a sore throat, an antigen test can show whether bacteria are the cause, which must be treated with antibiotics.
  
• Malaria: In some countries he checks whether there are parasites in the blood.

In laboratory medicine, antigen tests complement other methods such as the PCR test, which is more accurate but slower.

Why is the antigen test important?

The antigen test has a firm place in laboratory medicine because it has several major advantages:

• Speed: Results are almost instantaneous – ideal when you need to decide quickly whether someone is contagious or needs treatment.
  
• Simplicity: It does not require expensive equipment and can also be carried out outside a laboratory, for example in doctors’ surgeries or pharmacies.
  
• Cost: Antigen tests are cheaper than many laboratory tests, which makes them practical for a wide range of applications.

The test is particularly valuable in pandemics or outbreaks: it helps to stop infections early by allowing infected people to be isolated quickly.

What are the limits?

The antigen test is not perfect. Its greatest weakness is its accuracy:

• False negative: If the amount of the pathogen in the sample is too low – for example at the very beginning of an infection – the test sometimes misses it.
  
• False positive: Rare, but possible if the test reacts to something similar that is not a pathogen.

This is why a PCR test, which is more sensitive, is often added for important diagnoses. The antigen test is more of an initial indication – like a smoke detector that sounds the alarm but does not tell you exactly where the fire is.

The antigen test in Germany

In Germany, antigen tests became known primarily due to coronavirus. During the pandemic, they were available free of charge at test centers and many people took them themselves at home. Today, health insurance companies only cover them in certain cases, such as hospital stays. For other purposes, you pay for them yourself – around 3 to 10 euros per test. They have remained a standard tool in laboratory medicine, especially for infectious diseases that need to be detected quickly.

Conclusion

The antigen test is a practical aid in laboratory medicine. It provides quick answers, is easy to use and doesn’t cost much – perfect when it comes to keeping an eye on infections. Even though it is not as accurate as a PCR test, its speed makes it unbeatable. Whether for corona, flu or other diseases: The antigen test shows how modern medicine can be – fast, direct and accessible to almost everyone.

Editorial office: X-Press Journalistenbüro GbR

Gender note. The personal designations used in this text always refer equally to female, male and diverse persons. Double/triple references and gendered designations are avoided for the sake of better readability ected.