Covid-19: Re-testing previously diagnosed people before returning to work is ‘nonsense’

• Testing of people previously diagnosed before they can return to work must stop.
• Testing of people who do not fit a strict target testing criteria must stop.
• Whether the backlog of tests should be processed or not is “debatable”.

Testing of people previously diagnosed for Covid-19 to ensure they are no longer infectious before returning to work is “nonsense and must stop”, a top professor says.

Professor Wolfgang Preiser, the head of division of medical virology at the Department of Pathology at the University of Stellenbosch, said from now on, people who did not meet a strict criteria for targeted testing should not be tested.

Preiser is also a member of the Ministerial Advisory Committee (MAC) advising the government on Covid-19.

He said he could not divulge details of the MAC meetings, but added he could comment on issues that were public knowledge.

His comments come amid a heated debate between the Department of Health, Minister Zweli Mkhize and top scientists over the future of the country’s Covid-19 strategy.

The country faces an acute shortage of Covid-19 tests and has a backlog of about 63 000.

Professor Preiser said:

Some scientists, such as Professor Francois Venter an infectious diseases and HIV expert and head of Ezintsha at the University of Witswatersrand, have for weeks argued publicly for the department to stop mass testing and for tests to be reserved for hospitalised patients and healthcare workers. 

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Mkhize told News24 last Friday the country would move towards a more targeted regime, focusing on infection hotspots, hospitalised patients and healthcare workers.

“Going forward, it will be vital to avoid testing patients that do not fulfil the criteria or, even worse, people who are not patients, for example, those who may have been exposed and need to be quarantined,” Preiser told News24.

Exposure

“Here, a single test on day eight after last exposure to [Covid-19] can be done for essential workers like healthcare staff; if negative, the individual has very likely not been infected and can return to work, instead of waiting a full two weeks [before returning to work]; the five or six days saved [by returning to work] are important for highly needed professions.

“Testing of people previously diagnosed as infected, for example before they are allowed back to work, is nonsense and must stop; in uncomplicated cases, two weeks after [the] onset of illness and, in more severe cases, two weeks after coming off oxygen support is sufficient waiting time to make sure the individual is no longer infectious.

“Any testing in this context is unnecessary and wasteful. We have to make sure that tests are used only for those who will benefit from results, and then that they are done as quickly as possible,” he said.

Dr Jeremy Nel, another MAC member and head of infectious diseases at Helen Joseph Hospital, previously told News24 despite some low-yield testing requirements having been dropped, the testing strategy was “not moving fast enough in the right direction”. 

“There still isn’t a clear system in place to prioritise the tests coming from key groups, such as hospitalised patients, and healthcare workers [who need urgent tests so that we know if they can return to the frontlines early].

“This is despite the issue being raised publicly for weeks on end. Despite some reassurances from the NHLS top brass that such systems are in place, they are clearly not broadly operational – I’m not aware of a single hospital or lab in which the promised prioritisation systems are fully functional,” he told News24. 

Backlog

With a prioritised, targeted testing strategy comes the question of what to do about the backlog of tests in laboratories.

Venter and others have argued the backlog should be considered medical waste and disposed of.

Preiser said it was improving in the Western Cape, that urgent cases were being prioritised, although it was “debatable” whether all the samples in the backlog should be tested.

“We are well on our way to clear the so-called backlog here in the Western Cape; the backlog are samples that could not be tested at the time due to various reasons [mainly problems with getting test supplies, which is a problem globally].

“Whether this belated testing is still needed at all is debatable, but we do it while prioritising current specimens [which are urgent so that patients can be managed appropriately] so it does not compete with urgent work,” he added.

Mkhize told News24 the Western Cape’s backlog was being cleared, and the average turnaround time for tests there was 24 hours.

Preiser said, as part of the Western Cape’s recently adopted targeted testing approach, patients suspected of having Covid-19 were not tested if they were younger than 55 and did not have risk factors for severe illnesses.

They are advised to self-isolate at home and be vigilant for danger signs their condition is deteriorating.

Mkhize told News24 the issue of the disposal of samples in the backlog was complex.

“Some people were saying, oh, you need to discard them [the samples] after 14 days; others were saying after four days, others were saying after two days. We have asked the question, what is the basis for that? One argument was, we are wasting resources on the people who have not been tested that are in the backlog.

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“We felt that … we have made a lot of effort to try and cover the backlog by, firstly, asking SAHPRA [the South African Health Products Regulatory Authority] to deal speedily with the licensing of diagnostic tests that could be made available to make sure we have a very broad range of suppliers, to make sure we don’t get limited by the shortages that we are seeing.

“The SAHPRA has processed almost 200 kits to try and find the ones that will to be able to make us to get more access to that [tests]. So, I did say to the clinicians, that we must take this problem of the backlog as a short-term thing that we are going to get over,” he said.

Mkhize added ethical questions arose over how to inform patients who had been sent for testing that their tests would no longer be processed, and how best to inform them.

This would probably have to happen via their doctors, he said.

Turnaround times

Preiser said turnaround tests were not always a good measure to use when assessing the state of the Covid-19 response.

“These averages do not reveal the extremes, nor the spread. For example, while we may have had a few thousand samples a week old or older that yet had to be tested, we were testing others within 24 hours or even within two to three hours if highly urgent.

“The average may have looked bad, the reality on the ground was that we were providing a good service for current patients while we had failed some patients earlier; those who needed a test result that was not forthcoming often had subsequent sample sent as urgent which allowed appropriate clinical management,” he added.

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Nel told News24 the delayed turnaround time for tests was “not just an irritation”.

“It has several profoundly negative consequences in the healthcare system, including: having to open up new wards and beds within the hospital for patients who are awaiting their test results; having to use extra personal protective equipment and other consumables while awaiting test results; exposing staff unnecessarily to potentially infectious patients since more wards are necessary to keep patients who are awaiting results; potentially delaying important decisions about who should be ventilated or sent to ICU until results are available.”

He said the delayed results also made making hospital outbreak investigations almost futile.

“[Because] if results take several days to come back, the patient or healthcare worker may have infected several other people in the intervening time.”