Health: COVID-19 update |03 July 2020
More than 900 people tested so far
To date, the public health laboratory has tested a total of 954 people for the coronavirus using the polymerase chain reaction test.
Out of the 954 persons, 47% were suspected cases of COVID-19, 22% were those who needed to be tested before leaving quarantine, 17% were persons who needed to take the test prior to exiting Seychelles and 11% were persons who undergo ongoing screenings such as health workers.
Dr Emelyn Shroff, research director at the public health lab, disclosed these statistics yesterday in a press conference alongside Leon Biscornet, director of the public health lab.
Although 954 persons undertook the polymerase chain reaction (PCR) test, the public health lab conducted 1,040 PCR tests in total, which accounts for instances in which patients had to repeat the tests, either when their results came up inconclusive or if they were being monitored.
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.
Aside from the PCR test, which is used as the confirmative test for COVID-19, the health authorities also employ the rapid antibody test and, most recently, the rapid antigen test to screen for the virus.
A rapid antibody test detects the presence or absence of the antibodies Immunoglobulin G (IgG) and Immunoglobulin M (IgM), which are the human body’s response to the coronavirus.
On the other hand, the rapid antigen test uses nasal swabs to look for antigens (foreign substances that induce an immune response in the body) that are found on or within COVID-19.
“To date, the public health laboratory has done 1,092 rapid antibody tests […] and we have conducted around 100 rapid antigen tests since we only received it some three weeks ago,” Dr Shroff explained.
Mr Biscornet noted that the public health lab presently has the capacity to conduct around 100 tests for COVID-19 per day as it only has one machine.
“We are hoping to calibrate and fix a second machine after which we will be able to do some 250 tests, and a new machine, recently procured through the national disaster relief fund, might allow us to reach 1,000 tests per day,” he added.
In regards to the three false positive cases last week, Mr Biscornet noted: “We were made aware that these three persons were about to travel and in cases of travels, the lab uses two test kits to test for the virus whilst in the cases of patients who are sick we use three test kits. The level of accuracy is higher when we use three kits.”
“When we detected these three positive, using our screening algorithm, we had to re-confirm with new samples and by using three test kits. This is when all of their results came out negative.”
He noted that the public health lab’s capacity to detect COVID-19 is 98% efficient with a 2% margin of error.
“But I think we can all appreciate this fact; you would most likely take a test that has 98% efficiency. Additionally, in Seychelles, we use three test kits during the confirmation test which increases the level of sensitivity and provides higher accuracy.”
Mr Biscornet further explained that diagnostic tests are dynamic and are not only based on the test kits being used and their accuracy but also on the situation in a country.
“Based on the present situation in Seychelles, we expect to get cases of false positives. If we had a lot of positive cases in the country, using the same PCR algorithm, we would see that cases of false positives would decrease and we would get a lot of false negatives instead. This is the reality in countries like USA. And it is much better to have cases of false positives than false negatives,” he said.
Mr Biscornet noted that the public health lab never recorded a case of false negative among the initial 11 COVID-19 positive patients, who have already recovered.
As for the 70 seafarers who tested negative prior to their arrival in Seychelles and then tested positive on entry, Mr Biscornet highlighted that an investigation is underway to find out which tests the seafarers took at the two ‘Institut Pasteur’ labs located in Abidjan, Ivory Coast and Dakar, Senegal.
“The situation with the false positives has been a wake-up call for people in the society to realise that we should not be letting our guard down, we should continue to practice all the guidelines given by the health department,” Mr Biscornet provided as his concluding remarks.