Some of the experts have come up with a new theory saying that up to 90 percent of people who have been tested positive for COVID19, might not be carrying enough traces of the virus to infect others. The study says that it must be because of today’s tests are very sensitive. According to health professionals, widely used PCR diagnostic testing for coronavirus is too sensitive and they need to be changed to rule out those people, who have an irrelevant amount of virus, as they are usually not contagious. The PCR test used for testing COVID19 only examines if the patient is infected, it does not underline the amount of virus in the body.
PCR test examines the genetic matter from the virus in cycles and it usually takes 37 or 40 cycles, which detects even the smallest amount of virus present in the system that might not be a threat to the person. Health professionals have claimed that with less cycle threshold, it will be easy to identify those people who are at greater risk with a high amount of virus in their system. They have advised that extensive use of rapid tests along with an adjusted threshold might be crucial to zero in people with a high risk of infection. However, this suggestion seems to be exactly the opposite of newly altered testing guidelines in the United States. Recently, the US Centers for Disease Control and Prevention (CDC) has updated its testing guidelines saying that people, who do not have any symptoms, do not need to undergo any test unless they are vulnerable folks. However, many health experts have condemned the decision and called it a ‘backward’ choice.
The PCR tests, which are being used now these days have quite a high threshold, it can also detect the live virus. PCR tests can identify a few genetic fragments as well, which are kind of leftovers from a previous infection. That is the reason; experts are finding it difficult to determine high and low-risk patients. By adjusting its cycle approach, it will become convenient for doctors to identify those with a high risk of COVID19 infection. Experts have said that 30 or 35 cycles might be a reasonable cut off for the virus. Scientists have said that 85 to 90 percent of people, who have been tested positive for COVID19 with a cycle threshold of 40, would have tested negative if the threshold cycle were 30. CDC is already examining the use of cycle threshold to make a decision on it.