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CLAIM
“Dr. Anthony Fauci appeared to acknowledge that a large number of positive COVID-19 cases may result from hypersensitive tests that detect simple fragments of the virus rather than active and viable infections. If this is true, many patients may have received false positive test results ”
DETAILS
Incorrect: Regardless of whether a person tests positive with a high or low viral load, a positive test indicates that the person is or has been infected with the virus, which qualifies them as a COVID-19 case. The high number of COVID-19 cases reported in the United States is due to a large number of people infected, not the sensitivity of the PCR test.
KEY HOLD
PCR tests to detect viral diseases that have a high level of sensitivity can produce a positive result even if a person only harbors traces of viruses or non-infectious viruses, such as when patients recover. Therefore, a positive test result from a PCR test without additional viral load information cannot be used to determine whether an infected person should self-isolate or if their contacts should be traced. Even though a positive test on its own won’t tell if the person is contagious, it can confirm if the person is infected and is useful in monitoring the spread of the virus. It is therefore appropriate to count a person with a positive result as a COVID-19 case.
FULL CLAIM: “Dr. Anthony Fauci appeared to recognize that a large number of positive COVID-19 cases may result from hypersensitive tests that detect simple fragments of the virus rather than active and viable infections. If this is true, many patients may have received false positive test results – causing a lot of anxiety and unnecessary disruption in daily life – while the number of COVID-19 cases reported by health authorities public and major COVID tracking websites could be grossly overstated.
REVIEW
An article published by Just the News on November 8, 2020 claims that “many patients may have received false positive test results” and that “the number of COVID-19 cases reported by public health authorities and major COVID tracking websites could be grossly overkill. To support these claims, the article quotes statements by Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases, during a July 16, 2020 scientific podcast hosted by Vincent Racaniello, virologist and professor at Columbia University.
The podcast discussed the COVID-19 test and the value of the PCR test in educating those tested on what to do next. The PCR test detects the presence of the virus by amplifying a small part of the genetic material of the virus. The number of cycles of amplification required to arrive at a level considered to be a “positive” result is also called the cycle threshold value (Ct).
The Ct value depends on the amount of virus in a sample. The more virus present, the fewer cycles of amplification it takes to reach the level of a positive result, while a low viral load requires more cycles of amplification to reach that same level. Having a high or low Ct determines whether contact tracing and self-isolation measures would be helpful. This is because a high viral load (low Ct value) probably indicates that a person is infectious, while a low viral load (high Ct value) probably indicates that a person is not infectious or has low transmissibility. The video below, produced by Cold Spring Harbor Laboratory, provides a simple explanation of how PCR works in COVID-19 testing.
During the podcast, Fauci highlighted the problem with positive PCR tests with high Ct values, that many people with such results may no longer be contagious. This issue calls into question whether PCR tests are a practical way to inform a person infected with COVID-19 what actions to take after their diagnosis, especially if they are contagious and need to self-isolate. This consideration is also relevant in assisting public health authorities in determining whether contact tracing for that person is necessary.
Other experts have also expressed these concerns, as noted in this New York Times article. Michael Mina, epidemiologist and assistant professor at Harvard TH Chan School of Public Health, explained in the article that relying solely on the PCR test to inform people tested for COVID-19 what to do next may not be reliable. This is due to the high number of infections in the United States and the time taken for the PCR test to return a result:
“People infected with the virus are most contagious from a day or two before symptoms appear until about five days after. But at current testing rates, “you’re not going to do it often enough to have a chance of really capturing someone in that window,” Dr. Mina added.
Highly sensitive PCR tests appeared to be the best option for tracking the coronavirus at the start of the pandemic. But for the epidemics raging now, he said, it’s coronavirus tests that are fast, cheap and plentiful enough to frequently test anyone who needs it – even if the tests are less sensitive.“
However, several media outlets, including Just the News, have misinterpreted this information to suggest that the high sensitivity of the PCR test is responsible for the swelling number of COVID-19 cases reported in the United States and the actual number of infections. is lower than the reported figures indicate. . This inaccurate interpretation circulated in September 2020 and is based on New York Times article, which Just the News also cites. Health Feedback reviewed the complaint previously and found it to contain flawed reasoning.
As explained in the previous review, this claim does not distinguish between the test’s ability to confirm a COVID-19 infection – which the number of cases is measuring – and the test’s ability to determine contagiousness, which is the key issue that podcast and New York Times item address. The two categories are distinct. For example, recovering COVID-19 patients may still test positive for some time, as South Korea’s Center for Disease Control shows. This is because the PCR test cannot distinguish between infectious and “dead” (non-infectious) viruses.
the New York Times The article also states that when recovering patients, “tests with such high thresholds can detect not only live viruses, but also genetic fragments, remnants of infection that pose no particular risk.” Fauci also refers to these patients with the statement: “So I think if someone comes in with [a Ct value of] 37, 38, even 36, you have to say, you know, that’s just dead nucleotides, period. According to New York Times article, “Most tests put the limit at 40, a few at 37. This means you are positive for the coronavirus if the testing process took up to 40 cycles, or 37, to detect the virus.” However, the experts interviewed found that this figure was too high and that a better threshold for a positive result would be between 30 and 35, or even less.
Alternatively, the New York Times The article also points out that low viral loads can be detected by PCR tests on people who are in the early stages of infection, “The FDA has noted that people can have a low viral load when they are newly infected. infected. A less sensitive test would miss these infections. But these people could become infectious later when the viral load increases as the infection progresses.
It is incorrect to qualify these high Ct positive results as “false positives”. The term “false positive” indicates that a person has tested positive but does not have the disease[1]. However, a person who is or has been infected if their test is positive, whether the test has a high or low Ct value. It also means that it is appropriate to consider a person with a positive result and a high Ct value as a COVID-19 case.
Therefore, the sensitivity of the PCR test is not responsible for the high number of COVID-19 cases in the United States. Simply put, the number of COVID-19 cases is high because there are a lot of people infected. This indicates a high level of transmission of the virus in the community and public health measures, such as physical distancing and locks, are effective and important in reducing the number of COVID-19 infections and protecting the community.[2,3].
Apoorva Mandavilli, the reporter who wrote the New York Times article, also made this point in a Twitter thread, noting that “people who test positive but with an elevated CT * were * contagious, just earlier. They are no longer * contagious *. This does not mean that they have never been infected, so it does not affect the number of cases. “
To those who twist the PCR article to think that’s why the US numbers are lower: a big NOPE. People who test positive for PCR are infected, they simply may not be infectious.
– Apoorva Mandavilli (@apoorva_nyc) September 3, 2020
In summary, the claim that the number of COVID-19 cases in the United States is inflated due to the sensitivity of the PCR test is based on an inaccurate and misleading confusion of contagiousness with the presence of infection. The podcast and the New York Times The report highlights concerns about whether the results of PCR tests are useful in practice in determining whether a person is contagious, which has implications for the need for contact tracing and self-isolation. . The article and podcast also note that a potentially large proportion of positive PCR test results for COVID-19 occur in people with low viral loads who are unlikely to be contagious.
But the podcast and report do NOT say that people with positive test results and high Ct values have been misdiagnosed as cases of COVID-19. Regardless of whether the Ct value is high or low, a positive test indicates that the person is or has been infected with the virus, which qualifies them as a COVID-19 case.
In short, the high number of COVID-19 cases seen in the United States is due to a high number of people infected in the community, not the sensitivity of the PCR test. Therefore, public health measures, such as physical distancing and locking, are important in reducing the rate of infection in the community. Given the testing bottlenecks in the United States, the number of COVID-19 cases is much more likely to be underestimated, rather than overestimated, as these videos and articles claim.
REFERENCES
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