COVID-19 testing explained
Social media has been awash with a myriad of views regarding COVID-19 testing using either the Polymerase Chain Reaction (PRC) or the Rapid Diagnostic Test (RDT or rapid test) as the authenticity of test results is being questioned, leading to a decrease in interest by citizens to undergo testing.
Infocus News
To demystify the topic, Infocus News caught up with a Biochemist, Dr. Michael Bhebhe (PhD) who shared that the rapid test results are not conclusive, but play a critical role in screening potential COVID-19 cases before they can be verified through the PCR method which uses the principle of comparing genes of whatever infections found with those of the coronavirus.
“The reasoning behind this test is that the coronavirus has some structures on its surfacesuch that when the virus enters the human body, it triggers the immune system to produce antibodies coded as IgG and IgM.
“The general role of antibodies is to act as alarmists. Once something new finds its way inside the body, the antibodies go and attach on top of specific surfaces of those foreign, invading substances perceived as threats to peaceful body function. Once they attach onto that invader, white blood cells (soldiers of the body) will be alarmed to come as a backup squad to engulf and chew up that invader until it dies,” added Dr Bhebhe.
There are about 5 classes of antibodies, namely IgM, IgG, IgA, IgD, IgE. So far, it has been noted that coronavirus triggers antibodies IgG and IgM.
“If these are found in one’s blood, it might suggest that the individual either has the novel virus or has an infection which has surfaces similar to COVID-19, which may have triggered the circulation of either of these two antibodies IgG and IgM,” reiterated Dr Bhebhe.
Dr Bhebhe cited that when carrying out the rapid test, the cassette that is used for testing is packed with “chemicals” similar to those on the surface of COVID-19 and known to bind with antibodies IgG and IgM.
If either or both of these antibodies are present in the blood sample being tested and they bump onto the “chemicals” on the test cassette, they will bind and form a colour change from the white surface to a pinkish line. Once the pink line appears on either layers for the antibodies, the individual is diagnosed as a positive case (See picture below, cassette no. 32)
If the blank cassette turns from white to a pink line on this layer, it means that the individual being tested has been exposed to some infection (virus, and bacteria) which caused the body to secrete and circulate antibody IgG in the blood.
Dr Bhebhe said it is not ideal to assume that one who is diagnosed positive of these antibodies has COVID-19 until they are proven negative by the PCR method. He added that one should not have a sense of invisibility and security once they test negative.
“The result is only a snapshot of that particular moment, be it a positive or negative outcome. The moment you step out of the testing room, you might get exposed to the virus or your immune system might start manifesting IgG or IgM, such that the next text may come out positive in the nearest future.”
Dr Bhebhe implored citizens to be vigilant in maintaining good hygiene through frequently washing hands with soap and water or to use an alcohol hand rub or sanitizer, practicing social distancing and always wearing a face mask when moving in public places. He further encouraged citizens to ensure that surfaces such as door handles, tables, are cleaned using a disinfectant.
So far, Zimbabwe has recorded over 5000 positive cases.