The Chaos of False Covid Positives By Chris Knight (Florida)
What about false Covid positive tests, which are much more likely than the mainstream lets on, as covered below. The core problem lies in the hyper-sensitivity of the PCR test and the excess number of cycles it goes through. As for the resultant false positives, well, for one thing there is considerable mental anxiety generated. Here is one take on this.
“Far be it for me to care much about what goes on during ABC’s The View, but for the fact that this week provided a nationally televised example of just how much chaos false positive PCR tests can randomly inject into our daily lives.
One moment, it’s a normal day at the office, the next, as co-host Ana Navarro described it this week, “it turn[s] into an episode of Curb Your Enthusiasm.”
In case you missed it because you were watching literally any other show that doesn’t feature Joy Behar’s “sense of humor” as one of its selling points, ABC’s The View was stopped in the middle of live taping this past week when producers awkwardly asked Navarro and fellow co-host Sunny Hostin to step off the desk and leave the studio in the middle of an episode.
Co-host Joy Behar then went to proceed with a planned interview of Vice President Kamala Harris before being notified by her producer that it wasn’t happening.
When Navarro appeared on CNN later in the evening to speak to Anderson Cooper, she revealed that after being pulled off the desk, she tested negative on two separate Covid tests. Navarro took a rapid antigen test and a PCR test, both of which came back negative, she told Cooper. Hilariously, The Hill reported Navarro still couldn’t fly back home to Miami without taking a third test and waiting for a negative result.
“It takes so much work to do an interview like this. We were very proud to have the vice president come on 'The View' and then it turned into an episode of 'Curb Your Enthusiasm,' it was surreal,” Navarro told Cooper.
The incident isn’t one I’d normally care to write about, but for the fact that I exist on the fringe and enjoy asking questions that others won’t. Even though I consider most common sense Covid cautionary measures (like protecting the vulnerable, washing your hands and staying home when you’re sick) to be just fine, I have to ask: have we considered false positive tests when we consider the cost/benefit analysis of all of the combined Covid measures we’re taking?
We’ve talked about the mental health toll of keeping people locked down, we’ve considered the ridiculous nature of mask mandates and we’ve debated the merits of forcing small businesses and churches shut while Targets and Wal-Marts remain open for business.
I do understand the need to be extremely cautious around the Vice President of the United States, but this incident was a good reminder that false positive testing has been an issue that has slipped through the cracks and hasn’t been considered enough when we think about the downsides of our Covid response.
If testing positive for Covid upends your life and the lives of those around you, despite not having symptoms, what threshold would the rate of false positives need to hit in order for our often drastic reactions to be counterintuitive?
With antigen tests, the FDA says that false positives can occur at a range of intervals, between 4% and 70% depending on disease prevalence:
Remember that positive predictive value (PPV) varies with disease prevalence when interpreting results from diagnostic tests. PPV is the percent of positive test results that are true positives. As disease prevalence decreases, the percent of test results that are false positives increase.
For example, a test with 98% specificity would have a PPV of just over 80% in a population with 10% prevalence, meaning 20 out of 100 positive results would be false positives.
The same test would only have a PPV of approximately 30% in a population with 1% prevalence, meaning 70 out of 100 positive results would be false positives. This means that, in a population with 1% prevalence, only 30% of individuals with positive test results actually have the disease.
At 0.1% prevalence, the PPV would only be 4%, meaning that 96 out of 100 positive results would be false positives.
Health care providers should take the local prevalence into consideration when interpreting diagnostic test results.
Another pre-print study shows false positives using PCR tests between 0% and 16.7%
https://www.medrxiv.org/content/10.1101/2020.04.26.20080911v1.full
Abstract
Background Large-scale testing for SARS-CoV-2 by RT-PCR is a key element of the response to COVID-19, but little attention has been paid to the potential frequency and impacts of false positives.
Methods From a meta-analysis of external quality assessments of RT-PCR assays of RNA viruses, we derived a conservative estimate of the range of false positive rates that can reasonably be expected in SARS-CoV-2 testing, and analyzed the effect of such rates on analyses of regional test data and estimates of population prevalence and asymptomatic ratio.
Findings Review of external quality assessments revealed false positive rates of 0-16.7%, with an interquartile range of 0.8-4.0%. Such rates would have large impacts on test data when prevalence is low. Inclusion of such rates significantly alters four published analyses of population prevalence and asymptomatic ratio.
Interpretation The high false discovery rate that results, when prevalence is low, from false positive rates typical of RT-PCR assays of RNA viruses raises questions about the usefulness of mass testing; and indicates that across a broad range of likely prevalences, positive test results are more likely to be wrong than are negative results, contrary to public health advice about SARS-CoV-2 testing. There are myriad clinical and case management implications. Failure to appreciate the potential frequency of false positives and the consequent unreliability of positive test results across a range of scenarios could unnecessarily remove critical workers from service, expose uninfected individuals to greater risk of infection, delay or impede appropriate medical treatment, lead to inappropriate treatment, degrade patient care, waste personal protective equipment, waste human resources in unnecessary contact tracing, hinder the development of clinical improvements, and weaken clinical trials. Measures to raise awareness of false positives, reduce their frequency, and mitigate their effects should be considered.”
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