Imagine you go to the doctor because you’ve been feeling tired for weeks. You suspect that there may be something wrong with your thyroid gland. A blood sample is taken and a short time later the doctor knows whether your hormone levels are within the normal range. This is made possible by a procedure called immunoassay – an inconspicuous term that plays a huge role in laboratory medicine.

What is an immunoassay?

An immunoassay is a method used by doctors and scientists to detect certain substances in the body – for example hormones, vitamins, pathogens or drugs. The word “immuno” already indicates this: The test uses the principle of the immune system, or more precisely the ability of antibodies to specifically bind to certain substances. Antibodies are like tiny detectives that only search for what they know – be it a thyroid hormone or a virus protein.

The idea is simple: you mix a sample – usually blood, sometimes urine or saliva – with special antibodies that react to the substance you are looking for. If this substance is present, the antibody binds to it and this connection is made visible, for example through color changes, light signals or electrical impulses. The result shows: Is the substance present, and if so, how much of it? There are different types of immunoassays, such as the ELISA (enzyme-linked immunosorbent assay) or the chemiluminescence immunoassay, but the basic principle remains the same.

How does this work in practice?

Let’s take the example of the thyroid gland. The doctor wants to know whether you have too little or too much of the hormone TSH (thyroid-stimulating hormone) in your blood. In the laboratory, your blood sample is mixed with antibodies that only bind to TSH. These antibodies are often labeled with a marker – such as an enzyme or a glowing molecule. As soon as they find TSH, they trigger a reaction: In an ELISA, the sample changes color; in a chemiluminescence test, it glows. A device measures these signals and says: “Yes, TSH is present and the concentration is X.” All this often takes just hours – sometimes even less.

Why is the immunoassay so important?

In Germany, the immunoassay has become an integral part of laboratory medicine because it is fast, accurate and versatile. It is used everywhere: in hospitals, doctors’ surgeries and large laboratories. It is used particularly frequently in the diagnosis of hormonal disorders (such as thyroid or diabetes), infections (such as hepatitis or HIV) and even cancer by measuring tumor markers such as PSA (prostate-specific antigen). It is also worth its weight in gold in emergency medicine: an immunoassay can show within minutes whether someone is having a heart attack by detecting troponin in the blood.

A big plus point is its sensitivity. Immunoassays can find minute amounts of a substance – often in the picogram range (that’s a trillionth of a gram!). This makes them perfect for detecting disease early, before symptoms get worse. In a country like Germany, where prevention and early detection are a high priority, this is an invaluable advantage.

Significance for laboratory medicine

Laboratory medicine in Germany is highly developed, and immunoassays are a central component of this system. They complement other techniques such as mass spectrometry, which is even more precise but often more expensive and time-consuming. Immunoassays, on the other hand, are relatively inexpensive and can be carried out in large numbers – ideal for comprehensive care in a country with over 83 million people.

Automated immunoassay systems have long been standard in hospitals and laboratories. These machines can analyze hundreds of samples per hour, which makes diagnostics efficient. This is particularly important when it comes to routine tests, which are often billed under statutory health insurance. Immunoassays also play a role in research: they help to find new disease markers or monitor therapies, for example by checking whether a drug has the right concentration in the blood.

Opportunities and limits

The advantages are obvious: immunoassays are fast, accurate and flexible. In the pandemic, they have shown what they can do – antibody tests for corona were often immunoassays. They make it possible to test many people in a short space of time, which is crucial during waves of infection. They are also a key tool for personalized medicine, which is becoming increasingly important in Germany, because they can accurately measure individual values.

But there are also limits. Not every immunoassay is perfect – sometimes antibodies react with similar substances and give false results. This is called cross-reactivity. They are also dependent on known substances: When a new virus appears, a suitable antibody must first be developed. And with very complex analyses, they reach their limits – here the laboratory often takes over with other methods.

Looking ahead

The future of immunoassays in Germany looks promising. New technologies are making them even more sensitive and faster. Some devices will soon be able to test several substances at the same time – such as hormones and inflammation levels in one run. Digitalization is also helping: results are transmitted directly to the hospital network, which speeds up treatment.

In a healthcare system that focuses on quality and efficiency, the immunoassay remains an indispensable tool. It brings laboratory medicine closer to the patient, makes diagnoses more precise and faster – and ensures that doctors can make informed decisions. Whether in the emergency room or at the GP’s, the immunoassay is a silent hero that improves lives every day.

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.