What is rapid testing for coronavirus? Will it make Big Ten football safer? A (real) doctor explains.

The Big Ten will, you may have heard, attempt to hold a 2020 football season.

While the answer of “why?” is, of course, money, the justification Big Ten officials are using publicly is the ability to deploy daily rapid testing for student-athletes football players.

Rather than just nod at “rapid testing” like I had a clue what it means, I decided to reach out to a friend who is, unlike me, a real doctor: A doctor of infectious diseases, with degrees from a pair of Big Ten universities.

They were kind enough to offer me, so as to protect themselves and their employer, an anonymous but incredibly thorough overview of rapid testing for coronavirus.

The statements below are of a trained and licensed MD, not by a member of the Off Tackle Empire staff or SBNation.

The general idea: Could you go over the points of rapid testing?

Thanks for having me! I’ll start by noting this is a surface level overview meant to provide some context and background information to the readers. None of this is meant to influence policy (or politics).

And, finally, this is a new disease, and we are learning new things all the time, so things will certainly change as the science evolves.

The tests that have been most commonly used during this pandemic are Nucleic acid amplification tests (NAATs), which use a method called PCR to detect the nucleic acid (RNA) of the virus.

In general, these are great tests. When they give you a positive result you can feel confident it is a true positive (i.e., a low false positive rate), and the false negative rates are in general low as well. One major drawback of these tests is that you need a lab to run it, and a given lab may not have enough reagents/equipment to meet the testing demands. This is often what is happening when you read about people in the community getting a test but it takes days for them to get results (maybe you have experienced this yourself).

The “rapid” testing mostly refers to antigen testing. Instead of detecting nucleic acid from the virus, this detects a protein (“antigen”) that is found on the virus. The big advantage here is you don’t need to send it to a lab with PCR capabilities. You run the test [a swab or saliva sample] locally, often on a small machine, you get results quickly, often within an hour. Presumably, football facilities will have all the equipment available: everyone shows up and gets tested each morning, and they wait for the results before starting practice.

How effective are these tests?

PCR tests work quite well! The main drawbacks are the time, cost, and utilization of lab resources to make it happen, especially on a wide scale basis. If it takes someone five days to get their test result, that could be five days where they are at peak infectivity to others. Another drawback is because they detect nucleic acid, they may actually detect particles of “dead” virus that are no longer infectious (i.e., your body has cleared the infection but you still test positive because there is still some RNA hanging around).

With rapid antigen tests you eliminate (or significantly decrease) the time/cost concerns. Also, when a rapid antigen test is positive, this can generally be trusted — false positive rates are so far reported to be low.

False negatives are more of a concern. The CDC reports a sensitivity of 84-97% when compared to PCR — this means that out of 100 people with COVID-19 who take the test, you will accurately diagnose 84-97 of them, leaving 3-16% with a negative result. Likely, this data will evolve over time as it is used more.

While the potentially concerning rate of false negatives doesn’t sound great, one potential glimmer of hope is the distinction between “contagious” and “non-contagious” COVID-19. A current school of thought among some infectious diseases experts is that, if you have enough virus to be detected by the rapid antigen test, then you have enough virus to be contagious.

Whereas, if you are a “false negative”? Yes, you may have the virus, but likely you are not contagious. This has not reached the level of scientific consensus yet, but there have been some modeling studies that suggest that screening on a regular basis using antigen testing could be effective in limiting spread in congregate settings when combined with social distancing, masking, etc.

This 5 minute video is fairly helpful (caveat: some bias, made by a group that is a proponent of rapid testing for all):

The issue of follow-up testing for positive cases has been mentioned. What particular problems do false negatives create for Big Ten teams, and do you see any issues in the 5% threshold that could apparently shut down a team?

If I read the press release correctly, the B1G plans to confirm any positive rapid antigen tests with a PCR test. Hopefully the teams will first isolate all those with positive antigen tests, rather than just cross their fingers and wait on a PCR to be negative. In general, the PCR test is more tried and true, so trying to confirm makes some sense. However, rather than false positives, the larger question with the rapid testing is the false negative rate. As said above, the hope is that those with false negatives won’t be contagious, and they will just get caught on the next day’s test before becoming contagious. But have we tested this approach on a wide scale yet? Not really.

More broadly, I think out of all the available options (short of an NBA-style bubble), the B1G plan has probably the best chance of success in terms of preventing a large scale outbreak. But we are diving into unknown territory. I can’t say with 100% certainty that someone who initially has a false negative doesn’t spread the virus around a little before the rapid test picks it up the next day. And of course, daily testing does nothing to prevent them from picking it up around campus, in the community, etc.

Any other thoughts you think it’s important we know about rapid testing, monitoring, and preventing COVID as we move forward?

I think rapid testing is a good thing! For the general public, when the alternative is waiting 5-7 days, or perhaps not getting tested at all, rapid testing is likely a major improvement on a population level, even if there are false negatives.

Does it provide an ironclad fortress to keep COVID out of our football teams? This remains to be seen.

What else is there to say? How about just some bullet points?

• Herd immunity will probably be next to impossible without vaccination. Measles is the most contagious infectious disease known to man, with a reproductive number (Ro) of 12-18 (COVID-19’s is 2-3). In spite of this, we didn’t achieve herd immunity to Measles until mass vaccination started in the 60s (and of course, it has since made a bit of a comeback, but that’s for another day). Measles and SARS-CoV-2 are different viruses, so it isn’t apples to apples, but still a cautionary word worth considering.
• Vaccines will be here at some point, but will take time to produce and distribute.
• As things open up, your basic social distancing toolkit still applies. Masks are effective. The smaller the group size, the better. Outdoors is significantly better than indoors.

I don’t think any health expert would disagree that college kids are, overall, at a low risk for bad outcomes from COVID-19. The concern is that gatherings such as football games and all that comes with them could provide a vector to keep the virus alive in our society for longer.

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Special thanks again to my friend for taking time out of their schedule to answer these questions and clear up some of the uncertainties regarding rapid testing. If you have specific questions, I am happy to pass them on, though I can’t guarantee anything.