GARDEN ROUTE | HESSEQUA | KAROO NEWS - The backlog in Covid-19 testing in South Africa is due to a shortage in reagents, the main ingredients of the test kits used in the PCR (polymerase chain reaction) tests conducted on the nose and throat swab samples taken daily from thousands of citizens.
Wide-ranging testing has aided countries like South Korea to keep tabs on the spread of the novel coronavirus (Sars-CoV-2) that causes Covid-19.
According to Prof Gerhard Walzl, head of the Biomedical and Human Genetics Division of Stellenbosch University, the entire South Africa imports reagents from a few suppliers overseas.
"Although PCR tests can be produced in South Africa, the basic reagents need to be imported and these are just not sufficiently available. The tests have to undergo extensive validation and we cannot base clinical decisions on so-called in-house tests."
Testing instruments
Walzl said GeneXpert instruments (on which Covid tests are conducted) are readily available in South Africa as they are used for tuberculosis testing. Cepheid, the US manufacturer, has produced a Covid-19 testing cartridge that has several major advantages. The GeneXpert combines two steps of the PCR test (namely RNA extraction and PCR reaction) in one closed cartridge, it does not need a molecular biology lab or highly trained staff, and delivers results in under an hour.
However, the US government has restricted the export of cartridges and reagents.
The GeneXpert express test has one disadvantage. GeneXpert instruments available in South Africa are not particularly "high-throughput", says Walzl.
"Many instruments measure 1, 2, 4 or 16 tests at a time, although there are new instruments available that could do up to 2 300 tests per day, but these are not available here. I believe Cepheid is setting up production facilities outside the US to assist with the worldwide demand."
Cobas machines
South Africa also uses the Cobas system which Walzl says is a "high-throughput", automated test registered for emergency use due to the recent development of the CoV test. "There are different versions available which can each do 96 results in three hours, and depending on the instrument, 384 or 1 056 tests in eight hours. I am aware of one such instrument at the NHLS (National Health Laboratory Service) in Cape Town. The disadvantage is that samples have to be brought to the central lab before they can be assayed - a significant logistical challenge."
Closed borders
Walzl says test kits / reagents can be ordered from China, India or other Asian suppliers, but because of the grounding of flights and closed borders, they cannot get the material imported effectively. "So, it is all about a sudden and massive increase in demand worldwide, coupled with decreased production and transport of goods due to global lockdowns, import issues, and political decisions to restrict exports from countries like the US."
PathCare George testing up to date
Delene Brink of the PathCare George laboratory said their work schedule is "rough", but is going well.
"We have supply in reagents and are up to date with the Covid PCR tests that we are doing in George."
Related article: Backlog of 1000s in Covid testing
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