On Feb. 4, the COVID-19 Core Team sent out a campus wide email stating that ten samples from Week 4’s random surveillance testing were cross-contaminated and falsely identified as positive for COVID-19. The tests included eight students, one faculty member, and one staff member. All were notified of their false positive result within 48 hours.
The false positives were a result of cross-contamination at the University of Minnesota Genomics Center (UMGC), which processes PCR tests sent in from Carleton. The COVID-19 Core Team explained via email that “false positives on PCR tests are very rare but can occur when there is an error at the lab.”
When Carleton’s samples are sent to the UMGC, they are “initially processed in pools of five, and when a positive is detected in a pool, those samples are reprocessed individually to detect true positives.” The lab communicated that the cross-contamination and subsequent misidentification of the ten positive tests “likely occurred on the deck of the machine, resulting in not only the true positives being detected, but 10 negative samples on the same plate receiving low levels of positive signal from those positive samples.”
After testing on Monday, those who received false positives were notified on Wed., Feb. 8 of their positive results and moved into isolation that day. Sawyer Blair ’23, one of the students who received a false positive, was moved into a suite in the Alumni Guest House with another student who received an accurate positive test. “I moved into the same suite as one of my close friends who was already isolating and was very symptomatic. Nobody in the suite wears a mask because we all already have COVID-19, so what good is a mask?” said Blair. “I spent a lot of time in very close proximity to someone with COVID-19 who was coughing in my presence. We actually joked about me being asymptomatic saying that if I did somehow get a false positive, I definitely have COVID-19 now after spending time with her in isolation.”
Blair relayed that he was surprised to get the call that his COVID-19 test came back positive because he was “totally asymptomatic and wasn’t closely contacted in any capacity.”
Another student who received a false positive test, Madi Smith ‘22, was also surprised to receive a positive test: “I’m on the swim and dive team, so I’m regularly tested. I also try to reduce my exposure in order to be able to swim each week. So it was super surprising. Especially since all my roommates had negative PCR tests.”
Smith lives in an off-campus house and was not required to move into a separate isolation space after receiving the positive COVID-19 test. After self-isolating for two days, Smith received a call from Dean Livingston informing her that her test was a false positive. Smith said “Dean Livingston called me herself to let me know they re-ran my PCR. I felt relieved that I was free to be in isolation, but also frustrated that I was out there in the first place.”
Blair also received a call from Dean Livingston to learn his test was false-positive: “I got a personal call from Dean Livingston which was pretty sweet, actually.” Blair expressed confusion about how to react to the news: “I really didn’t know how to react or express my doubts. I didn’t want to stay longer in isolation if I didn’t need to, but I felt like I had been sent to isolation to get COVID-19 and then return to campus. It almost would have been easier if I had truly been positive, I wouldn’t have had to deal with the emotional rollercoaster of being positive, then not positive, but maybe still positive?”
Blair was just getting settled into his isolation space when he got the news of the cross contamination.
“The 48 hours in isolation was just enough time to get used to the idea that I had COVID-19, get all my stuff unpacked and moved in, figure out how to microwave the food so it wasn’t nasty and get settled into a new routine,” Blair said. “I was just about to start getting to the point where I could be academically productive when I got the call and was once again moving all my belongings across campus and trying to deal with the new plot twist in my story.”
Despite the relief of not actually having the virus, those sent into isolation because of the cross contaminated tests were emotionally and academically stressed by the experience. Blair explained the conflicting feelings of relief and confusion after finding out he didn’t actually have COVID-19.
“I feel academically derailed by the false positive — the stretch of days spent packing, moving, and adjusting were days I couldn’t do much schoolwork,” Blair said. “But since it was a false positive and I never had COVID-19, I feel pressured to be on top of my schoolwork like nothing ever happened, like I never was sent into isolation, like those lost days were ones in which I could have been productive. I’m now very behind on schoolwork, in a way that I definitely would not have been if my initial test had been negative, and in a way that I don’t think I would have either had I actually had COVID-19.”
After taking into account the ten false-positive tests and recalibrating the campus COVID-19 data, the College recorded 40 new cases of COVID-19 for the week of Jan. 29 to Feb. 4. 800 random surveillance tests were administered with an overall positivity rate of 1.54%. The 14-day campus positive rate dropped to 2.29%, a slight decrease from the week before.
Random Surveillance Testing will continue in the upcoming weeks in accordance with the Decision-Making Framework developed by the COVID-19 Core Team. The UMGC lab communicated that there has not been evidence of cross-contamination of Carleton samples before this incident and “assured [the College] that its procedures would catch future errors should they occur.”