COVID-19 Total Antibodies
COVID-19Total antibody

COVID-19 Total Antibodies

October 2, 2020


At Melio, we strive to offer you the best possible test on the market with the highest possible sensitivity and specificity. The Siemens Atellica IM COV2T test that Melio offers, was shown to be the most accurate, and the only one to meet MHRA's Target Product Profile (TPP), in a head-to-head comparison published by Public Health England in July 2020

Please note that it is not yet known if, or to which degree, COVID-19 antibodies can offer protection against future infection, or for how long any potential immunity will last. You should also know that some people may have recovered from a COVID-19 infection without having detectable levels of antibodies in their blood.

What are COVID-19 Total Antibodies?

A COVID-19 antibody test, also known as a serology test, does not detect the presence of the virus itself, but rather the response of our immune system against it. There are different types ('classes') of antibodies generated by our immune system after contracting COVID-19, the two most important ones are:

  • IgM: typically appears in the first week after exposure and disappears later

  • IgG: appears approximately 2 weeks after exposure and lasts for months or possibly even years.

The Siemens total antibody test gives you a combined IgM and IgG result, which means you'll find out if antibodies were detected, but not which class they belong to.

As of today, there is unfortunately not enough evidence that can guarantee that people who have recovered from COVID-19 and have antibodies are protected from a second infection. However, most experts expect that the presence of antibodies should at least provide “some level of protection”. Studies with respect to duration and strength of the protection conferred by antibodies are still ongoing.

The Siemens antibody test offered by Melio detects antibodies against the receptor-binding domain (RBD) of the S1 spike protein. The S1 RBD is currently the most common target of vaccine development as antibodies against S1 RBD can block virus entry into cells and therefore have a high likelihood of being neutralising (i.e. protective). As vaccine development is targeting S1 RBD, it is possible that to determine immunity, future blood tests post-vaccine may look at the presence of these antibodies.

Why is this test important?

Many people are curious to find out whether or not they've already had COVID-19. The most common symptoms, such as fever, dry cough and tiredness, are also common in many other infections. If you're curious to find out whether you've already had COVID-19, an antibody test is the best way to find that out.

Knowing if one previously was infected with COVID-19 is not only of interest to the tested individual, but also important from a public health point of view. As WHO Director General Tedros Adhanom Ghebreyesus said, “test, test, test” - testing is crucial in slowing the advance of the coronavirus pandemic. One of the strategies being employed by the NHS is to have widespread antibody testing amongst healthcare staff to determine whether immunity has been established in this cohort. Testing helps epidemiologists and policy makers better understand the prevalence, spread and contagiousness of the disease and tailor policies accordingly.

If you test positive for COVID-19 antibodies, you may also be able to help in the fight against COVID-19. The NHS needs people with antibodies to donate blood plasma (on a voluntary basis!) as part of a national effort against the virus. Right now the NHS is conducting clinical research to evaluate different treatments agains COVID-19, testing how effective convalescent plasma (plasma from people who’ve recovered from COVID-19) is for treating patients who are still ill. If you want to learn more about this initiative, click here.


What does a positive COVID-19 antibody test result mean?

A positive result could mean a past, recent, or even a current COVID-19 infection that has been going on long enough for antibodies to develop. The medical report that you receive from one of our doctors helps you interpret your test results in combination with your responses to the COVID-19 questionnaire that you fill out when you buy your test. If the test is taken as recommended, i.e. 3 weeks after symptom onset, it is most likely that a positive result will show recovery from a past COVID-19 infection.

The Siemens total antibody tests that Melio offers have a high specificity, which means that the risk for false positive results are minimal. Please note that it is not yet known if, or to which degree, COVID-19 antibodies can offer protection against future infection, or for how long any potential immunity will last.

What does a negative COVID-19 antibody test result mean?

A negative result for COVID-19 antibodies could mean that a person has never had COVID-19, or that they were only recently infected and antibodies have not had time to develop. You should also know that some people may have recovered from a COVID-19 infection without having detectable levels of antibodies in their blood.

When should you test your COVID-19 Antibodies?

Due to the relatively long time it takes for the body’s immune system to produce antibodies, the COVID-19 antibody test is not suitable to diagnose an acute infection. The purpose of this test is to find out if one has had COVID-19 in the past.

One week after the appearance of symptoms, antibodies can be detected in the blood in about 50% of COVID-19 patients. At 10 days after symptom onset, 75% of patients have detectable levels of antibodies in their blood. For the most accurate results, it is recommended to wait 3 weeks or more after the symptoms started, before taking an antibody test.

Other Considerations

  • No test can be 100% accurate, and false results are possible. At Melio, we strive to offer you the best possible test on the market with the highest possible sensitivity and specificity to avoid problems with false positive and false negative results.

  • A false positive results means that the result turns out positive even though the person does not have COVID-19 antibodies. This can for instance happen if there is a cross-reaction with other antibodies, such as antibodies against another coronavirus. A high specificity means that the test is highly specific to the COVID-19 antibodies, and that the risk of a false positive results is low.

  • A false negative result means that the person may have antibodies against COVID-19, but the test results still turned out negative. A high sensitivity means that the test is highly sensitive to detecting the antibodies it is testing for, and that the risk of a false negative result is low.

  • To interpret the results of the COVID-19 antibodies, it is important to take into account the symptoms, which is why we ask you to fill out a questionnaire about your symptoms and exposure. It may sometimes be necessary to complement an antibody test with an RT-PCR swab test.


What is COVID-19?

COVID-19, short for “coronavirus disease 2019”, is a respiratory infection caused by the virus SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2). SARS-CoV-2 belongs to the large family of coronaviruses, and was first discovered in Wuhan (China) in December 2019. The number of confirmed cases of COVID-19 has then been rising every day since.

COVID-19 presents with flu-like symptoms similar to SARS (Severe Acute Respiratory Syndrome) and MERS (Middle East Respiratory Syndrome Coronavirus), which are two other coronavirus-caused diseases that caused global outbreaks in 2003 and 2012 respectively. Although COVID-19 is much less fatal than SARS and MERS, it’s global spread is unprecedented.

The spectacular spread of COVID-19 around the world has led the World Health Organisation (WHO) to declare the COVID-19 outbreak as a global pandemic on March 11, 2020. As of June 7, 2020, there have been 6 799 713 confirmed cases and 397 388 COVID-19-related deaths reported globally (

Moreover, it is estimated that the “real” number of cases is significantly higher than those diagnosed. Calculations published by the Imperial College COVID-19 Response Team in April 2020 showed that infection rates vary between 0.5% of the population in Norway (with the lowest estimate) and 15% in the population in Spain (with the highest estimate).

The pandemic of a new virus that we still know little about poses a tremendous challenge to the global community. The UN Secretary General António Guterres calls the COVID-19 outbreak “the biggest challenge for the world since World War Two”.

Natural progression of COVID-19

COVID-19 is mainly transmitted through droplets generated by coughing and sneezing, but also when we talk. We can also catch COVID-19 by touching contaminated surfaces. Exactly how long the SARS-CoV-2 virus can survive outside the body is unknown, but other coronaviruses have been previously been shown to survive from a couple of hours to a week, depending on the material of the surface if not disinfected.

After infection, it can take from 2-14 days before symptoms appear. This is called the incubation period. The most common symptoms of COVID-19 are the following:

  • Cough

  • Fever

  • Difficulty breathing

  • Runny nose

  • Blocked nose

  • Sore throat

  • Headache

  • Nausea

  • Muscle and joint pain

It is also fairly common to lose one’s sense of smell and taste for a period of time. Diarrhoea has also been reported as a symptom.

According to the WHO-China joint mission report in February 2020, 80% of laboratory confirmed COVID-19 patients have mild to moderate disease, that is to say a flu-like presentation and does not require hospitalised care, while 13.8% has severe disease, with difficulty breathing and 6.1% has critical disease with respiratory failure, septic shock and/or multiple organ dysfunction.

Some people infected with the SARS-CoV-2 virus do not experience any symptoms at all. However, the exact proportion of asymptomatic carriers in the population and their role in the transmission of the infection is still unclear. Asymptomatic carriers of COVID-19 can only be revealed through testing.

There is currently no treatment that is fully effective or specific for the novel coronavirus, and those currently being used are either experimental or only partially effective.


Report from the American Society for Microbiology COVID-19 International Summit, 23 March 2020: Value of diagnostic testing for SARS–CoV-2/COVID-19. Patel R, Babady E, Theel ES, Storch GA, Pinsky BA, St. George K, Smith TC, Bertuzzi S. 2020., mBio 11:e00722-20.

Detection of antibodies against SARS‐CoV‐2 in patients with COVID‐19. J Med Virol. 2020;1–4. DOI: 10.1002/jmv.25820

The epidemiology and pathogenesis of coronavirus disease (COVID-19) Outbreak., Hussin A. Rothan. Journal of Autoimmunity.

Estimating the number of infections and the impact of non-pharmaceutical interventions on COVID-19 in 11 European countries. Department of Infectious Disease Epidemiology, Imperial College London; Imperial College COVID-19 Response Team. 30 March 2020

Coronavirus disease 2019 (COVID-19): Epidemiology, virology, clinical features, diagnosis, and prevention., Kenneth McIntosh, MD. UpToDate Apr 30, 2020

Performance characteristics of five immunoassays for SARS-CoV-2: a head-to-head benchmark comparison. The National SARS-CoV-2 Serology Assay Evaluation Group. Published Online September 23, 2020. Lancet Infectious Disease.

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