Rapid tests for virus the best way forward

I am a dad with two teenage boys who are about to go back to school. Like all other parents, I have anxiety about sending them to school these days. Even with the masks, social distancing and all other new protocols, there is little certainty that they will be safe.

But perhaps unlike most fathers, I am also a physician and a public health expert. I have traveled to Texas and Arizona at the peak of the pandemic to set up COVID19 test centers. Since March, I have spent hours providing consultation to various industries, from federally qualified health centers to mining and film studios, to advise them on testing, safe reopening and operations.

But no safe reopening strategy is more frustrating, or hits closer to home, than those of high schools. This September, my sons must meet an additional health requirement: a negative COVID-19 test measured by a test called rRT-PCR (realtime reverse transcription polymerase chain reaction).

It requires an advanced lab, trained personnel and a lot of time. The virus genetic material is extracted, then copied or amplified through many cycles of heating and cooling that take on average 6-8 hours.

Since no laboratory can perform and deliver these test results sooner than 48-72 hours, most schools accept the results from a test done two to three days earlier.

However, the scientific evidence does not suggest that this protocol is effective at all in detecting the infected cases.

This pandemic has created a public health crisis because the virus can spread from individuals with pre-symptomatic, symptomatic and asymptomatic infections.

That is why only a robust and reliable detection protocol, with a test that has a rapid turn-around time, is key here. The rRT-PCR, what everyone calls “the gold standard,” has been falsely billed. It is true that it outperforms other tests and has higher sensitivity. However, the sensitivity of this test during the first days of infection when there are no symptoms and the load of virus in the child’s nose may be low could be far from perfect.

In fact, several studies suggest that in the early days of the illness, its rates of false negative results could be as high as 29%, and a subsequent false sense of security.

Certain improvements on this test are under way. A simpler, cheaper and less invasive saliva test, or the “spit test,” has recently received FDA emergency use authorization. This is a step in the right direction. But the delayed reporting of the test results remains. Labs will have yet to develop capacity for the high volume of these tests.

The next issue is the three-day window between the time the student is tested and the time he/she will have the results. A lot could happen in that period, including new exposures.

More importantly, the child could have had a low viral load that was undetectable at the time of testing. A new study from South Korea shows that children under the age of 18 with COVID-19 cannot be identified by symptoms alone.

Twenty-two percent of the children who participated in the study never had symptoms during their entire course of infection, and another 66% had unrecognizable symptoms before diagnosis.

Such high prevalence of “silent COVID19 infection in children” means testing everyone at the beginning of the school year, then waiting for symptoms to test again, is not the right approach.

But what choice does the institutional policymaker have when the available PCR test is expensive and takes 2-3 days, in some cities up to 5-6 days, for the results?

Studies suggest that once the virus is replicating in the body, the viral load can go from several million to several tens of millions in a matter of hours. Therefore, the sensitivity of any test becomes less important.

Given the pattern of viral load and the “silent” nature of COVID-19 in children, the most effective test is one that can be done often, cheaply, with rapid turnover.

Several rapid tests are already available, and many more will soon be available. It is becoming increasingly clear that our control of this pandemic will rest upon the frequent use of rapid tests. Neither the strategy of no testing, nor testing only once at the start of the school year, is the right strategy.

The best strategy would be to use rapid tests on the first day of school, and as frequently as possible as dictated by a community’s prevalence data.

When it comes to choosing a test, the responsible thing to do is to prioritize accessibility, frequency and speed of reporting over all else.