Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2), the virus causing the novel COVID-19, has killed 40 people in Nigeria and over 200,000 in the world.
While testing has been a challenge, related to the inadequacy of kits, this explainer aims at informing its reader of different ways testing is done across the world.
Nigeria makes use of the Polymerase Chain Reaction (PCR) system in testing. Its West African counterpart, Ghana, uses both the PCR and rapid diagnostic test (RDT).
However, Ghana’s mode of testing has left many puzzled and questioning the accuracy of the method.
Prof. William Ampofo, Head of Virology at the Noguchi Research Institute, said the country tests samples in batches of 100. Therefore, a test of 1,000 results is actually 10 tests of 100 samples each.
“We simply pool the samples, meaning that, if you have 1,000 samples, you put them in groups of 10 and you test 100 pools at a time,” Professor William Ampofo explained.
“So in a short time, instead of testing 1,000 samples, you test 10,000 samples. This method we are using now was derived in 1945 and this very efficient way we have proceeded,” he said.
Dr Chikwe Ihekweazu, Director General of the Nigerian Centre for Disease Control, says that the testing method is not a road Nigeria wants to take despite respecting Ghana’s approach. He said it is better to be slow and get accurate results than rush into it and mess things up.
Below are the different methods of testing:
Rapid Diagnostic Tests based on host antibody detection
This test determines the presence of coronavirus by the presence of antibodies in the carrier’s blood.
This test has been found to be unreliable as antibody response vary by individual dependent on age, nutritional status, severity of disease or drug intake.
Studies have shown that majority produce antibodies two weeks after onset of symptoms. This makes it difficult to determine who is positive or negative.
Polymerase Chain Reaction (PCR)
This involves the testing of respiratory tract samples and is the recommended method for the identification and laboratory confirmation of COVID-19 cases.
PCR tests are used to directly detect the presence of an antigen, rather than the presence of the body’s immune response, or antibodies. By detecting viral RNA, which will be present in the body before antibodies form or symptoms of the disease are present, the tests can tell whether or not someone has the virus very early on.
It is worth noting that PCR tests can be very labour intensive, with several stages at which errors may occur between sampling and analysis. False negatives can occur up to 30% of the time with different PCR tests, meaning they’re more useful for confirming the presence of an infection than giving a patient the all-clear.
Lateral Flow Assay
Canadian firm Sona Nanotech has been attempting to push a completely different kind of rapid screening test for Covid-19 to market. It’s a quick-response lateral flow assay, and the firm says it expects its test to produce results in five to 15 minutes, cost less than $50 and be administrable by untrained individuals. Lateral flow assays have a wide array of applications and can test a variety of samples like urine, blood, saliva, sweat, serum, and other fluids.
Rapid In-clinic Antigen Testing
Bosch has also taken an innovative approach to Covid-19, developing a point of care swab test designed to produce results in under two and a half hours.
Running on Bosch’s pre-existing Vivalytic analysis device, the company says the test is one of the world’s first fully automated molecular diagnostic tests that can be used directly by all medical institutions.
Vivalytic consists of an analyser device and matching test cartridges. There are biological components in each of the cartridges that are used to prove whether a sample contains SARS-CoV-2 or nine other respiratory viruses. This eliminates the need for further tests if a patient doesn’t have Covid-19, but is presenting with one of the nine other infections.
The will be made available in Germany in April, with other European markets to follow.