Bisson: The Myth of Universal Testing

April 21, 2020

The Myth of Universal COVID-19 Testing

by Ken Bisson, M.D.

I did not vote for Trump in 2016 and I will not vote for Trump or Biden in 2020. I am a medical doctor with no allegiance to Republicans or Democrats. If leaders of either of these parties get something right, I rejoice. When either of these parties get something wrong — unfortunately far too often — I call them out.

As a physician, I have struggled to help my patients understand the scientific limitations of all medical testing. The public wishes to believe that test results are 100 percent accurate. That is never the case, and wishing it were so is dangerous. Using only tests that are 100 percent accurate would mean using no medical tests — zero.

Instead, we use tests that have fairly high accuracy and cautiously try to interpret the imperfect results we get. Physicians have to use the best tests available in the wisest manner. From my medical school days we were cautioned to “Treat the patient. Do not treat the test result.” The first thing to do when a test result did not agree with what we could see in our patient, was “repeat the test.” It was never 100 percent accurate.

Today I am frustrated that our public health experts are not frankly refuting claims that universal testing for Covid-19 is essential “before we reopen the economy.” Our Indiana State Health Commissioner avoids the difficult math behind the truth about universal testing by simply saying, “We have plenty of tests for those who truly need them.” That is true but is incomplete. The chief medical officer for the Indiana State Department of Health (ISDH), Dr. Lindsay Weaver, told physicians this week that today’s best RT-PCR test (for the presence of the Coronavirus that causes Covid-19) has a sensitivity of 70 percent among patients ill enough to need hospitalization. Among people who have mild or no symptoms, it is perhaps only 30 percent sensitive.

Simply put, the best laboratory test we have for identifying the SARS-CoV-2 virus misses 70 percent of all infected people tested when used for anyone other than the most ill.

How can that be? Stay with me for one simple example. The ISDH trending data suggest that the virus has infected perhaps 2 percent of all Hoosiers (remember, our documented cases represent only the fraction of all infected who became ill enough to be tested). If we employed universal testing for every 1,000 healthy-feeling Hoosiers, 20 would actually be infected. Of those 20 with the virus in their system, six would test positive and 14 would show a false negative result. The six with positive results will self-isolate for 14 days to limit the spread. The 14 with a false negative result will continue spreading the virus, just as they would have done with no testing. Perhaps they will even abandon social distancing after being misled by their universal testing false negative.

The low accuracy of the Covid-19 test is a relatively small problem when its use is restricted to people who are sick enough to be admitted to a hospital. Independent of their test results, all of these patients will be treated as if they are infected and all will eventually test positive on repeat tests done days later. However, the test’s low accuracy is a massive problem when used to test the healthy general public. Among the general public, it is likely only 30 percent sensitive. Are you ready to have nurses expend scarce personal protective equipment to insert an eight-inch swab far enough into your nose to reach the back of your gagging throat, to obtain a test result that will miss your infection far more often than it detects it? How many of these expensive tests should be purchased for 6.7 million Hoosiers? How many times do you wish to test every Hoosier to obtain such misleading results — weekly, daily?

All of this is explained well by Bayes’ Theorem of Mathematics. Only highly specific and sensitive tests qualify for screening a population that has a low probability of a positive test. (For math geeks, Google “Bayes’ Theorem — Math is Fun.” You can then contemplate the additional problem caused by the dozens of false positive results produced for every 1,000 tested.)

Again, testing healthy individuals with the best Covid-19 tests we have is worthless (or worse). Getting a negative test result means nothing when you are feeling well — tomorrow you may be ill and have a virus level high enough to possibly give a positive result. Many of today’s demands for universal testing seem to be politically motivated attacks — not based on scientific reality.

We repeatedly hear, “How can we open the economy before every American can be tested?” The medical reality is this: The most reliable evidence of Covid-19 activity in your community is whether there are currently folks becoming ill. As long as there are infected people in a community, a few of them will become sick enough to need the hospital. When no one is showing up for admission to the hospital with Covid-19 illness, your community has no active virus infections (at the moment).

So what is a governor to do? The proper role of our elected officials from the president down to county commissioners is to pass along the best advice of our health experts and let individuals make their own decisions. No president has enough information to dictate what is best for every state. No governor is wise enough to dictate what is best for every county. Only the individuals who know their own family needs and their own available resources can choose what is best for their family.

Hoosiers must not remain in lockdown until the false “magic bullet” of universal testing occurs. It never will be done because it cannot provide meaningful results among the general population. We can resume activity most safely by being vigilant to identify each new case of Covid-19 when one of us becomes ill, and then isolating all known recent contacts. Targeted testing of these individuals, along with healthcare workers and others in higher risk jobs, is necessary. Whenever Covid-19 activity has fallen for 14 days (as may be the situation in Indiana now) we must cautiously get back to work and monitor for every new case. Masks and social distancing will be with us for some time as we get back to work.

Dr. Ken Bisson, a founding adjunct scholar of the Indiana Policy Review, earned his bachelor’s degree in chemistry at Indiana University, Bloomington, and moved to Steuben County in 1980 to establish his medical practice after completing medical school at I.U. He raised four children in Angola and has 10 Hoosier grandchildren.


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