Laboratory Director at the Best-dos Santos Lab, Songee Beckles, has explained how the lab determines a positive test from the thousands of samples received on a daily basis, during the COVID-19 pandemic.
Ms. Beckles was responding to a query raised by Prime Minister Mia Amor Mottley regarding retesting samples due to the inconclusive nature of the first tests, during a media briefing at Ilaro Court to update the nation on the COVID-19 pandemic.
The Laboratory Director reasoned that the method used by lab officials involved a screening test and a confirmatory test and in the case of a test which may appear to be positive, a repeat is done on that test as well as on the confirmatory gene to ensure that it is a “true positive”.
She also clarified the testing range of the samples to give a better understanding about why some COVID-19 positive patients were asymptomatic, and still testing positive for the virus.
“What we look for from the PCR – we are looking for fluorescents. So, the virus, if it is present, is tagged to a fluorescent signal and in the machines that we use at the laboratory, it actually then detects that signal. For a person to become positive or to show up as being positive in our system, there is a cut off or a mark at which we say that the test is positive and then it is negative.”
Ms. Best continued: “That range of cut off means that the persons must come before what we consider the cycle or a cut off of 38. Once anyone is past that 38, it means any slight signal is actually a false signal or a negative. So for us, any person that comes up between 0 and 38 usually happens between 15 and 38 we would consider that person being positive for COVID-19. So, it can range from if we have persons that are doing very well or mildly ill, or even recovering, their actual cut off may be closer in the 30s – 35,38 – which means they are near recovery stages of the infection.”
For those persons in the acute phase of infection, Ms. Beckles said those persons usually showed up a lot earlier and in some instances, the lab has had persons who “show up as early as cycle 15 or cut off 15 then we consider them to be in the acute stage of infection.
In that stage you would expect that means they have a fairly high amount of virus in their system at that time”.
“For the majority of the persons that we have tested throughout and over the weekend, most of those persons were in the area of greater than 30 which means that we perhaps, picked them up as they are recovering and so they are actually more likely to be in recovery phases of the infection for most of them,” the Best-dos Santos Laboratory Director underlined.