Questions about COVID-19

Thursday, 05 March 2020 | Dr. Hendrik Borucki

Who is particularly at risk?

Persons over 60 years of age and patients with chronic diseases (e.g. high blood pressure, diabetes, cardiovascular diseases, chronic respiratory diseases, tumours) are at high risk of a severe course.

Children have a very low risk of severe courses.

Which smear kit should I use? With transport medium?

PCR swabs for nasopharyngeal smears are ideal. However, if necessary, you can use sterile cotton swabs and transfer them into sterile tubes.

Not suitable: Swabs with more than 2 ml of liquid culture medium, Q-tips and handkerchiefs.

Limited suitability: Swabs in gel medium because of reduced sensitivity.

"Mixed applications" - gel swabs for pathogen/resistance and influenza virus and/or coronavirus: both requirements from one material are not possible. Preference is currently given to viral detection.

You cannot request the PCR from a bacterial swab that has already been processed.

How do we store the sample until collection?

Please store the PCR samples at 4-8°C until collection. Room temperature is sufficient for transport.

Should we pack the samples specially for transport?

The normal outer packaging of the PCR swab tube in a leak-proof bag is sufficient, a special note on the bag is not necessary. The samples are transported by trained drivers.

How long does it take to obtain results?

As a rule, we inform you of the results within 24 hours. This time may be longer in individual cases if a sample has to be repeated. In general, the time needed for the results is longer if the sample volume is very high.
There is no obligation to notify us if only a differential diagnostic clarification is required.

A positive pathogen detection is reported by our laboratory (according to §7 IfSG).

How useful are the corona rapid tests now offered on the Internet?

These rapid tests are not suitable for the rapid and precise clarification of a suspected infection - for these reasons:

They indicate too late: Because these rapid tests measure antibodies against SARS-CoV-2, whereas the smear test detects the virus directly. Antibodies in a measurable amount are not produced by the body until a few days or weeks after infection. Detailed information on SARS-CoV-2 is not yet available.
They create false positives: a negative rapid test does not mean that the person tested does not spread the pathogen. Until his antibody level in the blood rises measurably, an infected person could therefore continue to spread the viruses.
They do not support the obligation to report: COVID-19 is a notifiable disease. A conspicuous rapid test result would have to be retested in the laboratory anyway before the health authorities receive the important notification of a new case. Valuable time may be lost. 

Pathogen detection by PCR remains the gold standard until more information is available on the sensitivity and accuracy of antibody rapid tests.

Does the so-called "pooling" of swab samples offer a relief with regard to reagent bottlenecks?

At least not the hoped-for one. Let's distribute 100 patient smears to 20 pools of 5 samples each and assume a positive rate of 10%. Then we use 20 tests instead of 100.

If the positive 10% are evenly distributed, every second pool would be positive and would have to be "dissolved", i.e. the swab samples would have to be re-examined individually. So measuring 10 pools with 5 swabs each again consumes another 50 tests. With the 20 pool tests before, the total number of tests is 70 instead of 100, so we do not save 80 percent of the number of tests, but only 30 percent.

Creating the pools and selecting the individual samples for re-testing is done manually. This is logistically demanding, error-prone, delays the notification of findings and requires a lot of working time. However, this is missing in departments that have to examine several thousand samples every day. In addition, it has not been conclusively clarified whether pooling does not lead to a loss of sensitivity under otherwise unchanged test conditions, especially when processing the samples.