False positive nasal swabs when testing for covid

https://journals.asm.org/doi/pdf/10.1128/spectrum.01695-22

This is an interesting journal article. Back in 2020, they tested lab participants that had worked with covid specimens and lab reagents associated with covid, they were asymptomatic, and they looked at what the results were of their nasal swabs. They were looking specifically at whether or not these lab workers were testing positive for COMMUNITY covid, of the DNA plasmid vector E-Coli associated with lab reagents used in testing. What they found was interesting.

“Asymptomatic laboratory workers who tested positive for SARS-CoV-2 for days to months were found to harbor a laboratory plasmid vector containing SARS-CoV-2 DNA, which they had worked with in the past, in their nasal secretions. While prior studies have documented contamination of research personnel with PCR amplicons, our obser- vation is novel, as these individuals shed the laboratory plasmid over days to months, including during isolation in their homes. This suggests that the plasmid was in their nasal tissues or that bacteria containing the plasmid had colonized their noses.” These participants tested positive for covid for weeks on end. But they did not have covid. It was a FALSE POSITIVE TEST due to colonized E Coli in their nasal passages from working in the lab.

“While plasmids are generally safe, our detection of plasmid DNA in the nasal secretions of laboratory work- ers for weeks after they had stopped working with the plasmid shows the potential for these reagents to interfere with clinical tests and emphasizes that occupational exposures in the preceding months should be considered when interpreting diagnostic clinical tests.”

Hmm. How many times have we suggested that the PCR testing for covid was inaccurate? Positive tests were not necessarily accurate. The PCR testing is used for so many different illnesses that false positives are quite common and it is not responsible to assume the positive swab was indeed covid.

In this experiment, we KNOW that the positive covid tests were false positive. “The coworkers had no known exposures to pandemic SARS- CoV-2. All subjects underwent 10 days of isolation in their homes and had home visits, with specimens collected aseptically by study personnel. The study participants remained asymp- tomatic throughout follow-up. SARS-CoV-2 antibodies were not detected in plasma from enrollment in any of the five cases or after 4 weeks of follow-up in the four coworkers.”

“SARS-CoV-2 was amplified from longitudinally collected nasal specimens from five asymptomatic individuals, four coworkers and one of their household members, which suggested person-to-person transmission of pandemic coronavirus. However, after the study team learned that a plasmid vector had been used in the month prior to enroll- ment by all four case coworkers in the laboratory outbreak, additional studies were performed to differentiate SARS-CoV-2 RNA from virus circulating in the community from DNA from the laboratory plasmid. Our inability to amplify regions of SARS-CoV-2 RNA outside the nucleocapsid that serve as targets in other diagnostic assays (1) did not support the presence of the pandemic SARS-CoV-2 in these nasal swabs.”

“Plasmid vectors, commonly used in research, can contaminate laboratory reagents (7) and biological samples (8), leading to false scientific claims (8, 9) or diagnostic results (2–4), which can create emotional stress for patients and divert health care resources to further tests. While plasmids are regarded as safe laboratory reagents, personnel handling plasmid solutions should use PPE and dedicated laboratory areas physically separated from spaces used for sample collection, processing, or nucleic acid amplification. Our novel documenta- tion of plasmid DNA in nasal secretions for weeks following exposure highlights the poten- tial for these reagents to interfere with molecular diagnostic tests performed on research personnel and emphasizes that occupational exposures occurring weeks to months in the past should be considered when interpreting diagnostic clinical tests.”

My question is this: how many “things” out in the environment that are breathed into our nasal passages could trigger a false positive covid test? How many covid positive tests were never covid but some other particulate or plasmid? If an individual has colonized MRSA in their nasal passages (many of us do), if they took a covid test would it trigger a false positive? My hypothesis is the PCR testing was never accurate to begin with, and it was something else triggering a positive among asymptomatic people taking a covid test. It did a great job spreading the fear factor though.