• Frequently asked questions on SARS-CoV-2 and the COVID-19 diagnostics

Below you will find the answers to frequently asked questions about SARS-CoV-2 and EUROIMMUN's tests for the diagnosis of COVID-19.


Do the test results of the EURORealTime SARS-CoV-2 and the Anti-SARS-CoV-2 ELISA (IgA and IgG) and Anti-SARS-CoV-2 NCP ELISA (IgG) allow drawing conclusions on infectiousness or immunity?

As long as the virus can be detected in the secretions of the respiratory tract by means of PCR, the patient is assumed to be infectious.

Unfortunately, the ELISA technique cannot show whether the detected antibodies have a neutralising effect on the pathogen. Such a finding can usually only be obtained by neutralisation test. Whether the IgG results obtained by ELISA may allow drawing conclusions on the immunity of a patient is currently investigated by scientific research. Generally, it can be assumed that immunity is associated mainly to class IgG antibodies as are detected by our Anti-SARS-CoV-2 ELISA (IgG). This is also indicated by the recently published results from the “Heinsberg Study” by the University of Bonn. The study underlines the high quality of the Anti-SARS-CoV-2 ELISA (IgG) and shows that the ELISA correlates very well with neutralisation assays.

Are the EUROIMMUN tests approved?

Both the EURORealTime SARS-CoV-2 and the Anti-SARS-CoV-2 ELISA (IgA and IgG) and the Anti-SARS-CoV-2 NCP ELISA are CE-marked and can be used for COVID-19 diagnostics. The Anti-SARS-CoV-2 ELISA (IgG) was also approved by the US American food and drug administration (FDA) through an emergency use authorization (EUA) for use by authorised laboratories, and by the Brazilian Health Regulatory Agency ANVISA.

Can the tests distinguish SARS-CoV-2 infection from infections with other coronaviruses?

EURORealTime SARS-CoV-2: Due to the detection of two specific gene sequences of the virus, SARS-CoV-2 infections can be reliably identified and delimited from other coronavirus infections.

Anti-SARS-CoV-2 ELISA/Anti-SARS-CoV-2 NCP ELISA: In the validation of the ELISAs, no cross-reactions to antibodies against worldwide distributed coronaviruses were detected. Cross-reactions with antibodies against the closely related SARS-CoV(-1), however, cannot be completely excluded. Nevertheless, it can be assumed that antibodies against SARS-CoV(-1) – the virus has not been circulating in the general public since 2003 – are no longer present to a significant amount in the population.

Can private persons perform our tests?

Please note that our tests are not rapid tests and can thus not be used for at-home testing. Our Anti-SARS-CoV-2 ELISAs (IgA and IgG) and the Anti-SARS-CoV-2 NCP ELISA (IgG) are designed for investigation of large sample numbers and require a laboratory infrastructure. Our PCR test EURORealTime SARS-CoV-2 is also designed for use in the laboratory. Cassette-based rapid tests for at-home use may present technical limitations such as reduced sensitivity or specificity. We do not offer rapid tests.

If you suspect to be infected with SARS-CoV-2, please ask your physician for a laboratory diagnostic test.

What are the application areas for the PCR and the ELISAs?

Direct pathogen detection via PCR is the method of choice to detect acute COVID19 infections. PCR allows for detection a few days after infection as well as in subclinical/asymptomatic infections. The virus can be detected up to 14 days after onset of symptoms. However, when the immune reaction starts and the viral load diminishes, the sensitivity of direct detection tests decreases. The pathogen can then no longer be detected in every patient.

Serological testing expands the diagnostic window over the first one to two weeks. By means of serology, those persons can be identified who present a persisting (no longer acute) or past infection with SARS-CoV-2.

Where can you buy our tests for COVID-19 diagnostics?

EUROIMMUN was one of the first companies to offer CE-marked test systems for the detection of antibodies against SARS-CoV-2 already in March 2020, i.e. the Anti-SARS-CoV-2 ELISAs (IgA and IgG). Our range of antibody tests for COVID-19 diagnostics has now been extended by the CE-marked Anti-SARS-CoV-2 NCP ELISA (IgG). Our EURORealTime SARS-CoV-2 test is also CE-marked. Both the ELISAs and the PCR test are designed to be used in diagnostic laboratories and are currently only despatched for this cause. They are not rapid tests for at-home testing.

If you would like a quote for our tests, please contact your local distributor.

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Which RNA extraction methods can be used for the EURORealTime SARS-CoV-2?

RNA extraction can be performed by any method (automatic or manual) which is suited and validated for the sample materials. The EUROrealTime SARS-CoV-2 test was validated with the QIAamp Viral RNA Mini Kit (Qiagen), the NucleoMag® VET Kit (Macherey-Nagel) and the CMG-2015 Prepito Viral DNA/RNA200 Kit (Chemagen).

Which laboratory equipment is required for performance of the SARS-CoV-2 ELISAs (IgA and IgG), the Anti-SARS-CoV-2 NCP ELISA (IgG) and the EURORealTime SARS-CoV-2?

Anti-SARS-CoV-2 ELISA/Anti-SARS-CoV-2 NCP ELISA: Photometer, 37°C incubator. For serological testing, we offer the CE-marked Anti-SARS-CoV-2 ELISAs for separate detection of the immunoglobulin classes IgA and IgG. The test kits include a 96-well ELISA plate (individual break-off wells, enabling adjustment to the actual number of samples to be analysed) and contain all reagents and control materials required for the test performance. Depending on the number of sera investigated per test run, up to 93 patient samples can be analysed with one test kits. Like other ELISAs, the test kits can be performed manually. Of course, the ELISAs can be also processed fully automatically on our EUROIMMUN Analyzer I and I-2P (Analyzer I: up to 7 microplates, up to 180 samples per test run, duration until the last result: 4:20h for IgG detection) and the EUROLabWorkstation ELISA (up to 15 microplates, up to 696 samples per test run, duration until the last result 3:28h for IgG detection).

EURORealTime SARS-CoV-2: The test is compatible with the standard equipment (real-time PCR thermocycler) present in most of the molecular-diagnostic laboratories. The EURORealTime SARS-CoV-2  was validated on the following real-time-PCR cycler: 7500 Fast Real-Time PCR Instrument (Applied Biosystems), LightCycler® 480 II (Roche), CFX 96 Touch (Bio-Rad). If customers want to use another cycler, they must validate it themselves.

Which antigen is applied in the Anti-SARS-CoV-2 ELISAs (IgA and IgG) and the Anti-SARS-CoV-2 NCP ELISA (IgG)?

The Anti-SARS-CoV-2 ELISAs (IgA and IgG) are based on the S1 domain of the spike protein (S) which is produced in a sophisticated procedure with a human cell line. This procedure allows representation of complex three-dimensional structures and post-translational glycosylations. Therefore also antibodies can be detected which exclusively react with authentic epitopes of SARS-CoV-2. Due to the use of this antigen, the Anti-SARS-CoV-2 ELISA detects antibodies with high sensitivity and specificity – cross-reactions with other circulating coronaviruses are significantly reduced. Moreover, the S1 domain contains the receptor binding site (RBD) of SARS-CoV-2 via which the virus binds to the human cells. Several publications describe that antibodies against this domain can probably prevent an infection with the virus. A positive antibody results could therefore indicate protection against reinfection with SARS-CoV-2.

The Anti-SARS-CoV-2 NCP ELISA (IgG) is based on a modified variant of the particularly immunogenic viral nucleocapsid protein (NCP). Antibodies against the nucleocapsid protein are typical markers for infections with SARS-CoV-2. The nucleocapsid protein in its full length, however, presents many homologies within the coronavirus family, which is why the occurrence of unspecific (false-positive) reactions with antibodies against other worldwide circulating human pathogenic coronaviruses cannot be excluded. Therefore, EUROIMMUN’s Anti-SARS-CoV-2 NCP ELISA (IgG) is based on a designer antigen in which unspecific conserved regions are eliminated, instead of the complete protein.

Which sample materials can be used for the EURORealTime SARS-CoV-2?

Validation of the EURORealTime SARS-CoV-2 test was based on RNA preparations of pharyngeal swabs. Other sample materials / sources of RNA can be used as well, but have to validated by the customer.

How long does it take to get the results?

Here, the shipping times of the sample to the laboratory and the capacities of the laboratory must be taken into account. The sole test performance is around 2 hours with the Anti-SARS-CoV-2 ELISAs (IgA and IgG) and the Anti-SARS-CoV-2 NCP ELISA and 1.5 hours with the EURORealTime SARS-CoV-2.

At what time after infection can the RT-PCR or the ELISAs be applied?

 

The WHO estimates an incubation period of 1 to 14 days for SARS-CoV-2, in most cases, it is approximately 5 days. This is the time that passes between the contact with the virus and the onset of first symptoms.

Even if there are no extensive studies available yet, it is assumed that the virus can be detected directly after symptom onset, in swabs of the lower respiratory tract, by means of RT-PCR.

In viral infections, antibodies are generally only produced at least one week, frequently two weeks after onset of symptoms and are detectable only then. Specific IgG antibodies can be detected with high sensitivity using the Anti-SARS-CoV-2 ELISA (IgG) or the Anti-SARS-CoV-2 NCP ELISA (IgG) approximately two weeks after symptom onset. A positive result confirms an assumed virus contact that took place some time ago. The Anti-SARS-CoV-2 ELISA (IgA) is suitable for monitoring of a developing immune response after positive direct detection.

Where can you get tested?

Our tests are exclusively performed in the laboratory. The required samples (blood, swabs...) are taken by a physician, e.g. your GP, and then sent to the respective laboratory in charge.

If you are interested, please get in touch with the Clinical Immunological Laboratory Prof. Dr. med. Winfried Stöcker (Seekamp 31, D-23560 Lübeck) which is performing the tests.

Can humans become infected by animals?

Several known coronaviruses circulate in animals without being transmitted to humans. All human pathogenic coronaviruses known so far are of animal origin. It seems that bats are a zoonotic reservoir of SARS-CoV-2.

How can I protect myself from the infection?

As with other respiratory infections, you should practice good hand hygiene, cover your mouth and nose, e.g. with a face mask, and keep a distance from infected persons. In view of the flu epidemic, these rules should basically always be followed.

Is there any specific medication or a vaccine available?

Currently, there is no proven medication or vaccine available against infection with the virus. Similar to the flu the symptoms of infected persons are treated.

Where do I find further information on SARS-CoV-2 and COVID-19?

World Health Organisation (WHO) https://www.who.int/

European Centre for Disease Prevention and Control (ECDC) https://www.ecdc.europa.eu/en/home 

What are coronaviruses?

Coronavirus constitute a large family of viruses which can infect humans as well as animals, for example birds and mammals. Coronavirus infection can lead to a simple cold, but also to severe or even fatal disease. The two highly pathogenic viruses SARS-CoV and MERS-CoV cause severe respiratory syndromes in humans. Infections with the other four human pathogenic coronaviruses (HCoV-NL63, HCoV-229E, HCoV-OC43 and HKU1) mainly only result in mild diseases of the upper respiratory tract. In babies, infants and elderly people, however, the infection can take a severe course.

How is SARS-CoV-2 transmitted?

SARS-CoV-2 is mainly transmitted via aerosols during coughing or sneezing or at close contact with an infected person. Health care personnel and family members are among the high-risk populations.

What are the symptoms of COVID-19?

The symptoms of SARS-CoV-2 infection are fever, coughing, breathing difficulties and fatigue. Most patients suffer from a mild febrile illness with irregular lung infiltrates. Some patients, particularly elderly or chronically ill persons, develop severe acute respiratory distress syndrome (ARDS), which is fatal in three percent of cases. In February 2020, the disease caused by SARS-CoV-2 was named COVID-19 (coronavirus 19) by the WHO.

How can COVID-19 be differentiated from other diseases such as influenza?

Due to the similarity of the symptoms it can be difficult to identify the disease based on the clinical picture alone. For this reason, laboratory tests are required that can reliably confirm suspected cases of COVID-19.

Which regions are currently affected by COVID-19?

The new coronavirus originated in the Chinese city of Wuhan, Hubei province. After the outbreak, the infection has spread rapidly over the country. For the latest information and case numbers, please refer to the WHO homepage.

What is the incubation time?

At present, there is only little information available on COVID-19 with respect to the time between infection and onset of the first clinical symptoms. Given current data, however, it can be assumed that the incubation period is three to seven, maximally 14 days.

How is a person tested for COVID-19?

Laboratory tests for the diagnosis of SARS-CoV-2 infection include polymerase chain reaction (RT-PCR) with smears from the upper and lower respiratory tract (bronchoalveolar lavage fluid, tracheal secretion, sputum, nasopharyngeal secretion, oropharyngeal secretion, etc.) for direct detection of the virus. The test is used for primary laboratory diagnostic examination of patients with suspected SARS-CoV-2 infection. Additionally, there are serological tests for the detection of antibodies against SARS-CoV-2 in the blood. The antibody test is the ideal supplement to direct detection. It supports the diagnosis of SARS-CoV-2 infection and helps to confirm the RT-PCR results. Moreover, the determination of antibodies is relevant for the clarification of suspected cases of SARS-CoV-2 without symptoms or with negative results in direct detection. In addition to their importance for diagnostics, serological tests can also be used to gather epidemiological data and for outbreak control. 

Can I become infected by an asymptomatic person?

It has lately been reported that persons infected with SARS-CoV-2 may already be infectious before showing the first significant symptoms. There were also reports about persons who became infected by patients with unspecific symptoms. Based on current data, mainly symptomatic persons are disease spreaders.