USC case finds glitch in conference testing system

The Pac-12 season has been a series of cautionary tales, but the latest installment caused us to do a triple take here at Hotline HQ.

Last week, USC announced four positive COVID-19 cases, which was both surprising and expected. Expected, because Los Angeles is experiencing 5,000 new cases per day, and USC is an urban campus in the middle of the inferno.

Surprising, because the Trojans — and UCLA — have done remarkably well navigating the pandemic and keeping their players safe. The Trojans conduct eight tests per week (six antigen, two PCR) and are as transparent as any program in the conference with regard to sharing relevant results.

The first of several news releases last week issued by the athletic department — all leading to a canceled game against Colorado and this week’s game against Washington State pushed back from Friday to Sunday — provided details on USC’s first positive of the season and gave the Hotline plenty to ponder.

“We were informed last night that a single football player tested positive for COVID-19 on Monday, Nov 23.

“That individual had traveled with us to Utah for Saturday’s football game, and he had tested negative three times within 36 hours of travel and again on game day. All other test results on Monday were negative ... The individual is symptomatic and has been quarantined.”

Think that through for a moment. Three negative tests over 36 hours prior to travel, a negative test on game day, and then positive and symptomatic by Monday — which likely means the player was symptomatic by Sunday afternoon or evening.

Typically, the amount of virus that’s detectable by testing precedes by 24-to- 48 hours the amount of virus that’s required for symptoms. Yet the USC player tested negative repeatedly through Thursday, Friday and Saturday morning ... and then was symptomatic by Sunday evening.

Had he been tested a few hours later, it might have shown up. Either way, that’s a narrow window for him to have turned positive — narrow enough that I wondered if the Trojans had been hit by a false-negative: Could the player actually have been positive on Saturday morning as the game-day tests were being conducted?

The Hotline turned to an expert who has helped us throughout the pandemic: Dr. George Rutherford, an epidemiologist, biostatistician and the director of UCSF’s Public Health Group.

Here’s the testing cadence for the USC player:

Thursday morning: antigen test/negative

Thursday morning: PCR test/ negative (result available Friday)

Friday morning: antigen test/ negative

Saturday morning: antigen test/negative

Sunday: no test Monday morning: symptomatic and positive

So we asked Rutherford about the potential for a false-negative on game day — an antigen test that would have been administered by SafeSite, the Pac-12’s third-party testing operator.

Rutherford was skeptical of the theory and pegged Wednesday as the likely infection point. With that as Day Zero, Rutherford explained, the player would have turned positive on Day Three — Saturday — via the ultra-sensitive PCR testing technology.

But PCR tests typically require a 24-hour turnaround and aren’t feasible on game day. The conference uses rapid-response antigen tests on Saturdays, but they are less sensitive. Rutherford estimated that the player’s antigen test would have turned positive late Saturday or sometime Sunday (Day Four), with the symptoms appearing by Monday (Day Five).

“This is a pretty standard timeline,” he said.

Our takeaway: The Pac-12 tests more than any conference in the country, but the cadence still might be vulnerable to midweek infections. If a player becomes infected on Wednesday, then he’s likely to remain negative through the late-week and pregame testing, but possibly turn positive — and contagious — on Saturday afternoon, evening or night.

For road teams that test late morning or early afternoon and then play night games and fly home, this is particularly risky. With a Wednesday infection, the day-of-game testing might be too soon; the Monday morning testing might be too late.

The closer pregame testing is to kickoff, the better — of course, that depends on the turnaround time required by SafeSite. Taking that a step further: Teams should consider testing the travel party on Sunday, back on campus.

To this point, Sunday has been a test-free day, because players are off. But the conference’s official protocol states: “Daily pointof-care testing on each day of full practice, higher-risk of transmission activity, travel, and games.”

Technically, Sunday could be considered a day of “higher-risk transmission activity” because the post-night game flights home are invariably in the wee hours.

Yes, it’s another strain on the football program’s infrastructure. But theoretically, it would seal off a transmission window on Sunday, when players gather outside of football activities.

And if a player tested positive, it would allow for more immediate contact tracing than if the teams waited for Monday testing. USC was unlucky with the timing of the positive case but might have been fortunate with the damage.

As far as we know, no infections have been traced to that player, which suggest he was not contagious until sometime Sunday (whether or not the gameday test was a true or false negative). To make the Trojans’ situation even more fraught, they were the victims of a false-negative antigen test during the week and several false positives, according to a conference source.

Whether that player then infected others isn’t clear at this point. The antigen tests are known to generate false positives, and the Pac-12 has accounted for that possibility with the requirement that teams perform confirmatory PCRs in those instances.

But false negatives? That’s like trying to counter an eight-man blitz with five blockers: Someone’s getting through — it’s only a matter of how much damage is caused.