Prof. Dr. Jürgen Rockstroh's notes and advice on COVID-19 - Part 2: TESTING

  • Ana ŠARIĆ
  • Univadis
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Prof. Dr. Jürgen Rockstroh, an infectious disease doctor from the University Hospital in Bonn and current president of The European AIDS Clinical Society is walking us through the current state about COVID-19 testing.

All right, so let's talk about issues around testing.

So, in Germany we started off with performing swabs, mostly nasopharyngeal swabs or just deep pharyngeal swabs, and then subsequent PCR testing. And this seems to be great if there is clinical suspicion for a COVID-19 or in patients who where you expected they had contact with someone who was definitely positive and maybe in the asymptomatic phase but highly viraemic in the upper respiratory tract. But please note that in the further course of the disease the viral load in the upper respiratory tract tends to decline, ad some patients who come late with pneumonia already present may be negative in the PCR but have CT findings which are suggestive of COVID-19 disease. Clearly here specimens from the deeper respiratory tract are necessary, including, for example, expectorated sputum and a tracheal aspirator or bronchoalveolar lavage in ventilated patients. So that's important to keep in mind.

Now, these tests were available very soon in Germany, and I think one of the big differences in the epidemiology for the German country which is basically a pretty fast rise in found cases, but a very low mortality rate is because a lot of asymptomatic patients with COVID-19 infection were identified. That is really I think one of the good success stories of the German approach that actually by doing testing early you can find people and put them into quarantine and prevent transmission to others, and I think that really is one of the most important messages from the whole testing from Europe where in some countries only patients were tested when they were symptomatic in late stages of the disease and were admitted to the hospital, so obviously you miss all the other ones who have a benign course or are asymptomatic early in their infection and then can transmit to others because they're not isolated. So I think that's one of the very important messages around testing.

There have been attempts to also look at other tests, including rapid tests which obviously would facilitate testing a lot, but there have been some methodological issues, and so far that is not available for routine use. Then there are attempts to develop serologic testing, so that would be done by currently immunofluorescence or ELISA testing, and you would detect antibodies, again, COVID-19. Now, this is not so useful for acute diagnosis, because it takes a while to develop these antibodies. 50% of patients show antibodies after seven days of symptoms, but they do not correlate with viral load, and then obviously the question is, is it still replicating disease or is it a sign of past infection? After 14 days, all subjects studied showed antibodies.

Now, I think the serologic, and this will be important maybe in the near future when you want to assess whether people working in the hospital already have had the infection, because then obviously if they had the infection, that may protect them against another infection, and they may be used more easily in the healthcare setting. Also, people who want to visit potentially relatives or so, knowing whether they had a past infection or not may be helpful, but for the acute diagnosis this is not going to play any role.

The German capacity for testing is relatively good, but clearly still needs to be expanded, because in some places there are not enough tests available, and people have been sent away or had difficulties finding places where they could be tested, despite having, for example, a partner who tested positive, and obviously for further quarantine measures and so forth it's important to know the diagnosis. Currently, around 200,000 tests are performed per week for a population of a size of 83 million inhabitants, and there clearly are attempts to increase testing, particularly in the context of the discussion of loosening the lockdown and making people move around more freely. This may be important, because the more reliably you can test everyone who has the infection, particularly early on and send them to quarantine, the more likely you will be to prevent further onward spread of transmission of the virus.