ISSUES AROUND COVID-19 TESTING

…A typical Covid-19 Drive-thru Test Site

Our president is keeping the US in last place in dealing with Covid-19

If you can believe the screwed-up Covid testing we have in the US, just check out the kind of questions you get when you go to a testing site here in the SF Bay area.

A couple of local residents went to a test site as they were taking the test for screening purposes before spending a week in a shared house with two other couples. Their risk seemed small because they had no symptoms and no known exposures, as did the other couples.

When they got to the test they were asked: “Do you want the faster one or the more accurate one?”  Another friend and local resident had also been asked the same question at their test site:

The faster test would give a result within 24 hours. It had a very low false positive rate but a 20% false negative rate, meaning that if the result was positive, they almost certainly had Covid-19, but if it came back negative, they still had a 20% chance of having the disease. The more accurate test had a very low false and false negative rate, but because of the testing backlog, they wouldn’t get the result for 10 days.

The reality is that the question of “Do you want the faster one or the more accurate one?” , this is the basis of the current United States testing strategy.  That is, if we actually do have a testing strategy.

In the absence of widespread testing that is both fast and accurate, there’s only one question to ask to determine which test you need: What is your risk of Covid-19?

If the risk is low, the fast test is enough. In the case of the first couple, they were taking the test for screening purposes before spending a time in a shared house with other low-risk couples. Their risk was small, because they all had no symptoms and no known exposures.

Their trip was in two days, so a 10-day lag would mean they wouldn’t know anything until after their trip.  And if they had taken the test 10 days before, they would have gotten the result before they left, but they would still have had 10 days to be exposed to the virus.  What they needed was the fast screening test.  If that came back negative, they could be fairly confident that they were okay.

If the risk is high, however, the fast test isn’t enough: You need the accurate one. The fast test however, can still serve as an initial screen.

Now, say there’s an elderly nursing home resident who has fever and a cough. An initial positive test will quickly confirm Covid-19. But the likelihood of the novel coronavirus is so high that the accurate test should still be done if the initial screen were negative.

Someone with a medium risk would benefit from this approach as well.

If a doctor had a patient who was exposed to someone who subsequently tested positive. If the patient felt fine and it was a brief exposure, he may be OK.  But if he has young children at home, it’s not practical for him to isolate from his family for 10 days while awaiting the more accurate test.  He should instead get the rapid test, which if negative, he should also get the more accurate test just in case.

This framework of risk approach is used in medical decision-making all the time.  In screening for cancer, heart disease and much more. Those deemed to be low-risk have a quick screening test. If it’s negative, evaluation usually stops. Those with higher risk will continue with more extensive testing.

But here’s how this approach would apply when it comes to national policy decisions.

The Covid-19 test that we have been depending on is the polymerase chain reaction or the PCR test. This is the more accurate test that requires processing in a laboratory and has long wait times in many parts of the country.  Averages in July were running about four days, and 10% of patients waited 10 days or more, according to a national research survey. 

We can ease the demand for this test by ramping up production of another test: the antigen test. These tests don’t require laboratory processing and can provide results in as little as 15 minutes. Moreover, the PCR test can cost hundreds of dollars, while the antigen test costs at little as $1.

Why not invoke the Defense Production Act to immediately mass produce these less accurate, but much faster and cheaper screening tests? They are already being made available in India and Senegal, and some versions are FDA-approved in the United States. Imagine if we had enough of these tests that, every morning, all children and teachers could take one at home.  Imagine if restaurants and other retail establishments required them as a condition of entry. Imagine if one could take a home test before getting together with extended family. How much safer would we all feel, and be?

But with the current man in the White House, this will never fly.

Some would say that the antigen tests just aren’t accurate enough. But the alternative is people not being tested at all. Catching 80% of asymptomatic cases is a lot better than catching zero.

Others might say that we shouldn’t deny people the more accurate test. But we currently have limited resources and we are rationing tests as I write the article. We shouldn’t leave it to chance to determine who receives what test, or whether people get one at all.

As we have heard for months, the lack of testing is our country’s Achilles’ heel in the fight against Covid-19, and I wonder who’s responsible for that??????

A tiered strategy can help identify far more infections than we do now.

It’s time we get the right test to the right people, but with the current administration, I’m not holding my breath until they get their act together.

Copyright G. Ater 2020