How does the coronavirus screening test work? Is the test accurate? Read on to learn about the science behind the coronavirus screening test…

The science behind the coronavirus screening test

“Testing, testing, testing” was the mantra repeated again and again by World Health Organization Director-General Tedros Adhanom Ghebreyesus. Laboratory-based diagnostic testing and immunoassay screening devices that identify active coronavirus infections in people are vitally important for public health efforts, as well as individuals’ health concerns. Widespread diagnostic testing, along with isolation and quarantining of those infected, seems to have been key in South Korea’s work to suppress the spread of the virus.

Polymerase chain reaction (PCR) is the most commonly used test for the laboratory detection of coronavirus (SARS-CoV-2) because it is highly accurate. The PCR test starts with sampling, which usually involves using a nasopharyngeal swab, which looks like a long cotton bud that draws mucus from the back of a patient’s nasal cavity where it meets the throat.

“PCR has high sensitivity and selectivity”, which means it correctly spots almost all the positive cases and correctly rules out almost all the non-infected cases, says Steven Wolinsky, an infectious diseases physician at Northwestern University in Illinois, USA. “That makes PCR a really good diagnostic test.”

However, the turnaround time for results from the PCR test is a huge disadvantage. Each test takes about 4 hours once a sample reaches a testing laboratory, with the time split between sample preparation and the actual PCR test. With transport and queues, getting a result can take 2–4 days. In that time, infected people may have spread the virus to many others.

Rapid immunoassay antibody screening for Coronavirus

Recent studies suggest that a high percentage of patients show no or few clinical symptoms. This means that they may be unwittingly spreading the virus. For this reason, a rapid screening method has been developed.

The AlphaBiolabs IgM-IgG Combined Antibody Rapid Test works by detecting both early and late marker IgG/IgM antibodies in human finger-prick blood samples. Results can be made available within 15 minutes of taking the test. This accurate test is similar to the type that was widely used in China by the Chinese CDC to help identify COVID-19 infections. Screening for COVID-19 IgM and IgG antibodies is an effective method for the rapid diagnosis of COVID-19 infection. It can also provide information on the stage of infection, so for example, if you currently have the coronavirus infection, if you have had the infection in the previous 6 weeks, or if you haven’t had it at all.

How does the coronavirus screening test work?

Immunoglobulin M (IgM) is the body’s largest antibody. As the figure shows, it is also the first antibody to appear in response to an initial exposure to an antigen (a toxin or other foreign substance), which induces an immune response in the body. IgM provides the first line of defence during viral infections, followed by the generation of adaptive, high affinity Immunoglobulin G (IgG) responses for long-term immunity and immunological memory.

This means that:

  • Detection of IgM antibodies tends to indicate a recent exposure to COVID-19.
  • Detection of IgG antibodies indicates a later stage of infection.

The results are displayed in the detection window of the testing device. There is no need to send any samples away for testing.

The AlphaBiolabs IgM-IgG Combined Antibody Rapid Test is available on our website. Alternatively, please contact our Customer Services team on 0333 600 1300, or email