Hygiene in context with corona

Dr. Schumacher’s online portal is aimed at hygiene managers and specialists working in healthcare facilities. Contributions from research and practice are intended to provide well-founded information during the current COVID-19 pandemic – for better implementing hygiene and infection prevention measures.


What is the difference between PCR test, antigen test and antibody test?

In Germany, the main test used to detect SARS-CoV-2 is the PCR test. However, other tests are now available, such as antigen and antibody tests. The various tests differ in terms of how they are carried out, how long they take and how reliable they are.

PCR test
Polymerase chain reaction (PCR) is considered the gold standard among coronavirus testing methods. The PCR laboratory test is the most reliable method for diagnosing a SARS-CoV-2 infection. It has the highest sensitivity and specificity for detecting the novel coronavirus.

For the PCR test, a swab is taken from deep inside the mouth, nose or throat. As an alternative to the swab, the so-called gargle test can be used. The person being tested gargles with a special solution for approximately 30 seconds so that particles from the throat get caught in the solution. The sample material obtained from the swab or gargle test is multiplied and analyzed in the laboratory. Using special stains, the virus material can be made visible and the virus concentration can be determined. The test procedure itself takes approximately four to five hours. However, given the time it takes to transport the tests to the laboratory, the preparation time in the laboratory and the waiting time due to the large volume of samples, it can be several days before the test result is available.

Rapid PCR test
Instead of being sent to a laboratory, the polymerase chain reaction can also be carried out in a rapid procedure using a cartridge. The results of this test procedure are available in about two and a half to three hours, but rapid PCR tests are considerably more expensive and less reliable than laboratory tests.

Antigen test
The antigen test detects the protein structures of SARS-CoV-2 and works in a similar way to a pregnancy test. It involves taking a swab from deep within the mouth, nose or throat, or alternatively a gargle test. The sample material is placed on a test strip. If there is viral material in the sample, the protein components of the virus react with the test strip causing it to change color.

The test result is available in less than 30 minutes and the cost of the test is comparatively low. In addition, the test procedure is easy to do without needing the services of a laboratory. However, antigen tests are generally less sensitive than PCR tests, which means that a larger amount of virus is necessary to indicate a positive result.

Furthermore, rapid antigen tests are less specific than PCR tests. In other words, a positive result is often indicated even if the person tested is not infected (false positive). Consequently, a positive antigen test result needs to be confirmed by a PCR test.

Antibody test
The antibody test detects the immune system’s response to SARS-CoV-2. If viruses enter the body, the immune system produces antibodies after a few days, and they fight the virus. These virus antibodies can be detected in the blood. Since this test reflects the delayed body reaction, it is not suitable for detecting an acute infection. Antibody tests can be carried out in the laboratory or as rapid tests.

Bundesministerium für Gesundheit, Die nationale Teststrategie – Coronatests in Deutschland, 7. Dezember 2020, https://www.bundesgesundheitsministerium.de/coronatest.html(Letzter Zugriff am 14.12.2020).
Robert Koch-Institut, Hinweise zur Testung von Patienten auf Infektion mit dem neuartigen Coronavirus SARS-CoV-2, Stand: 30.11.2020, https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Vorl_Testung_nCoV.html;jsessionid=3A72B0757FBFD2F5BCCC1240F72C4977.internet101#doc13490982bodyText5(Letzter Zugriff am 14.12.2020).

Do surface disinfectants that are used to kill COVID-19 have to contain certain concentrations of active ingredients?

No. Any proven “limited virucidal agent” is sufficient for reliably inactivating enveloped viruses such as SARS-CoV-2. Evidence based on test methods according to the German Association for the Control of Virus Diseases (DVV) or EN 14476 or EN 16 777 (for products without mechanical/spray disinfection) proves that these surface disinfectants reduce viruses by at least 4 log-10 units under the standard conditions that were tested. This means that out of 1 million virus particles, a maximum of 100 remain. The Robert Koch Institute also recommends using limited virucidal agents against COVID-19.

All marketable products that are labeled accordingly achieve the required effectiveness. The fact that the formulations and mixtures of active ingredients may be very different and also contain different concentrations of active ingredients does not make a difference to the effectiveness.

However, if pure active ingredient solutions are used instead of marketable products, certain concentrations have been identified as necessary. This has been shown by a review that evaluated 22 studies. These studies mainly used pure active ingredients in aqueous solution and no marketable products were used. None of the alcohols mentioned in the studies that were examined had a lower or medium active substance content, meaning no statement could be made about their effectiveness against coronaviruses.

With this in mind, the German research team came to the conclusion that when using pure active ingredient solutions, the following concentrations must be used in order to inactivate coronaviruses: Ethanol: 62–71%, hydrogen peroxide: 0.5% or sodium hypochlorite 0.1%. The studies showed that other agents such as 0.05–0.2% benzalkonium chloride or 0.02% chlorhexidine digluconate were less effective.

Conclusion: The review of the studies does not allow conclusions to be drawn about products on the market: Disinfectants available on the market are often have formulations that are much more complex than pure active ingredient solutions in water and are optimized for the individual usage conditions. For example, certain formulations may also contain small amounts of benzalkonium chloride and yet the product is still effective due to the entire formulation. Therefore, it’s not a specified active substance content that makes a marketable surface disinfectant suitable for inactivating SARS-CoV-2, but rather evidence of the limited virucidal agent documented by current test methods and standards.

How to process medical devices that have been in direct contact with COVID-19 patients?

The Robert Koch Institute (RKI) recommends that all medical devices, such as stethoscopes or electrodes, that have been in direct contact with COVID-19 patients should always be used in on a patient-specific basis.

The medical devices must be disinfected after use. During transport, care should be taken to ensure that the transport containers are closed properly and are disinfected on the outside. Thermal disinfection methods are preferred for processing medical devices. According to the RKI, the thermal processes used in washer-disinfectors offer more reliable efficacy, such as reduced impairment due to residual contamination for example.

If thermal processes are not possible, the RKI recommends the use of disinfectants where the limited virucidal agent has been proven to be effective at least.

Robert Koch Institute, recommendations from the Robert Koch Institute on hygiene measures in the treatment and care of patients with a SARS-CoV-2 infection, as of 04/01/2020.
https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Hygiene.html (Last accessed on 04/07/2020)
Robert Koch Institute, hygiene requirements for the processing of medical devices, October 1st 2012.
https://www.rki.de/DE/Content/Infekt/Krankenhaushygiene/Kommission/Downloads/Medprod_Rili_2012.html (Last accessed on 04/07/2020)

How can laundry and textiles from COVID-19 patients be safely reprocessed?

It is possible to safely reprocess laundry and textiles from COVID-19 patients by following the recommendations of the Robert Koch Institute using a disinfecting laundry disinfection procedure according to the RKI list.
The list describes the different processes and active substances such as the required concentrations of disinfectants and detergents as well as liquor ratio, temperature and exposure time. It is important to remember that the washing machines used for this purpose should also comply with the required parameters. This means that the washing machines must be operated in accordance with the operating instructions, be serviced regularly and checked to ensure they function properly.
COVID-19 patients should use disposable tissues as handkerchiefs. It is recommended that covers that can be disinfected by wiping are used for beds and mattresses.

RKI. List of disinfectants and disinfection methods tested and approved by the Robert Koch Institute. As of: October 31st 2017 (version 17). https://www.rki.de/DE/Content/Infekt/Krankenhaushygiene/Desinfektionsmittel/Downloads/BGBl_60_2017_Desinfektionsmittelliste.pdf (Last accessed on 04/07/2020)
Recommendations from the Robert Koch Institute on hygiene measures in the treatment and care of patients with a SARS-CoV-2 infection.
https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Hygiene.html (Last accessed on 04/07/2020)

What are the criteria for visitation regulations in care homes and nursing homes during the COVID-19 pandemic?

In principle, the following applies: Whether and under what conditions a care home or nursing home should allow visitors is decided by the home itself, depending on the local situation and possibly in consultation with the public health department.

However, the following aspects should be considered in general:

  • It is preferable that social contact is made via telecommunications, such as telephone calls, and not through personal visits.
  • If someone is displaying signs of a cold, they should stay away from the home. The same applies to people who have been in contact with someone who is infected with COVID-19.
  • If a home decides to permit visitors, each visit must be registered (visitor’s name, date of visit, name of the resident visited). Furthermore, visits should be kept to a minimum and visitors should be informed about the necessary protective measures. This includes maintaining a minimum distance of 1.5 to 2 meters from the resident, wearing protective gowns as well as a face covering and disinfecting your hands when leaving the resident’s room.

Robert Koch-Institute, Prevention and management of COVID-19 in care homes and nursing homes and facilities for people with disabilities, Recommendations for care homes and nursing homes and facilities for people with disabilities and for the public health service, status: 4/14/2020. https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Alten_Pflegeeinrichtung_Empfehlung.pdf?__blob=publicationFile

„Hygiene in context with Corona“
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