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Questions over rapid testing kits

Testing for the coronavirus at a laboratory in the United States

Grenada is to begin deploying several strategies for conducting mass testing among the population in its fight against COVID19.

Coordinator for the country’s National COVID19 response, Dr George Mitchell has said that there will be random testing of people who show up at health clinics and those who call the COVID19 hotline.

He said that Grenada is now in possession of 3000 Rapid Test Kits, a gift from Venezuela.

“We are going to be deploying several strategies to maximise the testing among the population,” said Dr Mitchell at a press conference Monday.

The objective, according to Dr Mitchell is to find out “what percentage of the population has been affected”.

Grenada has recorded 14 laboratory confirmed cases of COVID-19 out of 92 PCR lab tests.

In a scientific brief published on its website on April 8, the World Health Organisation (WHO) said the following, regarding the rapid test kits now being used by many countries: “In response to the growing COVID-19 pandemic and shortages of laboratory-based molecular testing capacity and reagents, multiple diagnostic test manufacturers have developed and begun selling rapid and easy-to-use devices to facilitate testing outside of laboratory settings.

“These simple test kits are based either on detection of proteins from the COVID-19 virus in respiratory samples (e.g. sputum, throat swab) or detection, in blood or serum, of human antibodies generated in response to infection.”

However, this means of testing has not been fully endorsed by researchers nor the WHO.

The scientific brief went on to say: “At present, based on current evidence, WHO recommends the use of these new point-of-care immunodiagnostic tests only in research settings. They should not be used in any other setting, including for clinical decision-making, until evidence supporting use for specific indications is available.”

Rapid diagnostic tests based on antigen detection and rapid diagnostic tests based on host antibody detection that detects the presence of antibodies in the blood of people believed to have been infected with COVID-19 which appears to be the method Grenada issuing.

The WHO said: “How well the tests work depends on several factors, including the time from onset of illness, the concentration of virus in the specimen, the quality of the specimen collected from a person and how it is processed, and the precise formulation of the reagents in the test kits.

“Based on experience with antigen-based RDTs for other respiratory diseases such as influenza, in which affected patients have comparable concentrations of influenza virus in respiratory samples as seen in COVID-19, the sensitivity of these tests might be expected to vary from 34% to 80%.

“Based on this information, half or more of COVID-19 infected patients might be missed by such tests, depending on the group of patients tested.”

There are other difficulties with rapid test kits. Hundreds of thousands of kits purchased from Chinese manufacturers are being found to be defective and in some cases the accuracy of the test is as low as 30 percent.

Countries such as Spain and Britain have recalled more than a million kits.

It is not known whether the rapid test kits being used in Grenada came from Chinese manufacturers and a question regarding this which was posted to the Ministry of Health Facebook page by a journalist was deleted by the page administrator without an answer being provided.

One of the companies which supplied the defective kits is Shenzen Bioeasy.

In response to complaints, a company spokesperson blamed the incorrect results on “a failure to collect samples or use the kits correctly,” adding that the company had not properly communicated with buyers on how the kits worked.

The Chinese government, which has been positioning itself as the saviour of the world, donating medical supplies to 120 countries, has tried to limit the damage, pointing out that the company in question has no license to export test kits, but Bioeasy claims that its products are certified for sale in Europe.

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