The science behind COVID-19 tests that could save the season

The Pac-12’s return to competition depends on one unexpected development solving two momentous problems.

The late September arrival of rapidresponse antigen tests — two months earlier than anticipated — will allow football teams to test players for COVID-19 immediately before practice and games, thereby preventing

on-field transmission by presymptomatic or asymptomatic players.

Those same antigen tests, courtesy of a partnership with San Diego-based Quidel Corp., are central to clearing the other hurdle: Convincing health officials in Oregon and

California to lift state restrictions and allow the six teams to move forward with practice and competition.

The three NFL teams in California long ago received exemptions from the state, in large part because of their ability to test players on a daily basis. The Pac-12’s testing plan, however, isn’t identical to the NFL model.

It’s better.

“From a theoretical perspective, it’s a very high bar, and you could argue that what we’re doing is a higher bar” than the NFL, said Dr.

Kimberly Harmon, a University of Washington football physician and key member of the Pac-12’s medical advisory team. “The near-daily testing should keep the athletes safe.”

The Pac-12 would be wise to make that very case to authorities in Oregon and California — the sooner the better — in order to avoid getting left behind in what could be a costly race.

The Big 12 and ACC are playing. The SEC gets underway in two weeks. The Big Ten is on the brink of restart

ing its season, possibly in the middle of October.

At that point, the Pac-12 would be the only member of the Power Five on the sideline. The perception of the conference nationally, already poor, would deteriorate further.

“That’s on top of everyone’s minds,’’ commissioner Larry Scott told KJR radio in Seattle last week. “But health and safety take precedence.”

The rapid-response antigen tests are an escape hatch for the Pac-12— a means of keeping the players safe and salvaging the conference’s reputation. They’re expected to arrive by the end of the month, for use on a daily basis by athletes in six contact sports: football, men’s and women’s basketball, men’s and women’s water polo and wrestling.

Harmon believes implementation could take several days, at least. Each school must train staff members to administer the tests, record the results and report the data to local health agencies.

Waivers must be signed. Testing space must be created. Protocols must be established.

“It’s not as simple as going

to the drug store and buying a pregnancy test,’’ she said.

If the antigen tests are in place by early October, the conference could begin an abbreviated season in early-to-mid November -- but only if Oregon and California lift their restrictions.

(Scott told KJR that it was “highly unlikely” the conference would proceed without all 12 teams.)

While Oregon Gov. Kate Brown and her staff have hinted they would not let the Beavers and Ducks get left behind the rest of the conference, the political challenge in California isn’t so much about clearing a hurdle as it is climbing El Capitan.

Example No. 1: The Rams opened their season at home Sunday afternoon, but seven miles away, USC cannot congregate in groups of more than 12 players.

Example No. 2: The 49ers opened at home on Sunday afternoon, but 15 minutes up the road, Stanford is prohibited from having more than two players touch the ball on any given play.

The key difference in the level of state restrictions, Hotline sources believe, is the testing: With their immense resources, NFL teams can conduct daily PCR tests to prevent the spread or the virus. In contrast, the

Pac-12 teams have been unable to test players daily. But that will change when the Quidel antigen tests arrive.

Harmon’s comparison of the Pac-12 testing plan to the NFL’s model required a qualifier — “from a theoretical perspective” — because the rapid-response antigen tests aren’t as sensitive as the PCR tests and haven’t been in use for as long.

But according to data from the medical experts’ presentation to the presidents in August, the antigen tests should be more effective than the PCR tests in driving down the rate of infection.

That information is based on research by a handful of scientists that included Colorado assistant professor of computer science Daniel Larremore and Michael Mina, an epidemiologist and immunologist at the Harvard School of Public Health. In a preprint of their paper published earlier this summer — it had not been peer reviewed at the time — the authors determined that “testing frequency was found to be the primary driver of population-level epidemic control.”

Frequency, not sensitivity, is the key to containment because of the rate the virus grows once it enters the body. Scientists believe that infectiousness occurs

when there are approximately one million copies of the virus (per milliliter) in the body, Harmon said.

But unless a contagious person coughs in your face for 10 minutes, a typical COVID-19 exposure doesn’t instantly produce one million copies — it could be more like 50,000 or 100,000 copies. Because of exponential growth, that initial figure could become one million copies within 24 or 48 hours.

Now, overlay that growth rate with the different testing protocols.

The PCR tests used by the NFL have a 24-hour turnaround time because of the need for a reagent to amplify the DNA and RNA, and for a laboratory machine to process the sample.

Depending on the time the PCR test is administered to an NFL player, his viral load at that moment and the time required for results to become available, a player could unknowingly take the field with an infectious level of virus.

It’s not likely, but it’s possible — hence the 98 percent reduction in infectiousness assigned to the daily PCR testing regimen by the Larremore and Mina study.

“There’s a little window when it can sneak in,’’ Harmon said.

The antigen tests made by

Quidel are not as sensitive as the PCR tests — they don’t detect the virus until higher loads levels have been reached. But they’re more effective in reducing infectiousness because of the 15-minute turnaround time.

Here’s how the antigen tests, in theory, would prevent viral spread across the Pac-12:

Let’s say a player is tested before practice and is positive. That’s easy: He’s held out and isolated. If the player tests negative, that could mean 1) he’s truly negative (no virus in the body) or 2) he’s infected, but not at a level that would register on the antigen test.

And that’s OK, because if the viral load doesn’t register on the test, it’s not significant enough to be infectious. Immediately after the negative test, the player could participate in a full-contact practice (or game) without risking transmission because the virus won’t reach the one million copies threshold during the window of close contact.

“In the four hours I’m playing,” Harmon said. “I’m not infectious.”

The next day, that same player would have enough copies to test positive, and the isolation process would begin. The 15-minute turnaround time, in theory, eliminates a contagious player from suiting up.