AUSTIN (KXAN) — On Monday morning, the term “Space Karen” trended across Twitter after one doctor took aim at Tesla CEO Elon Musk for complaints he made about recent COVID-19 test results.

Last week, Musk tweeted that ‘something extremely bogus’ was happening after he took four COVID-19 rapid antigen tests. He reported that two of the tests returned positive results, the other two were negative.

“Same machine, same test, same nurse,” Musk elaborated in the tweet.

But in a reply that same day, Dr. Emma Bell, who according to her Twitter bio is a bioinformatics postdoc at the De Carvalho Lab in Toronto, laid out Musk’s claims, saying: “Rapid antigen tests trade sensitivity for speed. They return a result in <30 minutes, but can only detect COVID-19 when you’re absolutely riddled with it. What’s bogus is that Space Karen didn’t read up on the test before complaining to his millions of followers.”

Bell followed up her argument with a piece on her blog, titled, “No, Elon Musk is not about to blow this COVID-19 testing thing wide open.” There, she explained that rapid antigen tests — which the FDA approved in April and likened to at-home pregnancy tests — are only accurate during a certain window of time.

According to Bell, these tests work by detecting a protein found on the surface of virus particles — but these particles (and proteins) peak as people begin to experience symptoms. She says that outside of this peak, it’s likely a rapid antigen test can provide a negative result.

“Thus, a rapid antigen test may well return a false negative when an infected person most needs to isolate. The White House’s over-reliance on rapid antigen testing may have contributed to their super-spreader events,” Bell writes.

She concluded by saying: “The three types of COVID-19 test available — PCR, antibody, and rapid antigen — each have their limitations. They ask the question “Is there evidence of COVID-19 in this sample?” in different ways. It’s important we understand those limitations and differences when interpreting results.”

Meanwhile, Twitter went wild with Bell’s Musk moniker.