https://www.nytimes.com/2020/08/29/h...s-testing.html

Your Coronavirus Test Is Positive. Maybe It Shouldn’t Be.

By Apoorva Mandavilli
Published Aug. 29, 2020
Updated July 3, 2021

Some of the nation’s leading public health experts are raising a new concern in the endless debate over coronavirus testing in the United States: The standard tests are diagnosing huge numbers of people who may be carrying relatively insignificant amounts of the virus.

Most of these people are not likely to be contagious, and identifying them may contribute to bottlenecks that prevent those who are contagious from being found in time. But researchers say the solution is not to test less, or to skip testing people without symptoms, as recently suggested by the Centers for Disease Control and Prevention.

Instead, new data underscore the need for more widespread use of rapid tests, even if they are less sensitive.

“The decision not to test asymptomatic people is just really backward,” said Dr. Michael Mina, an epidemiologist at the Harvard T.H. Chan School of Public Health, referring to the C.D.C. recommendation.


“In fact, we should be ramping up testing of all different people,” he said, “but we have to do it through whole different mechanisms.”

In what may be a step in this direction, the Trump administration announced on Thursday that it would purchase 150 million rapid tests.

The most widely used diagnostic test for the new coronavirus, called a PCR test, provides a simple yes-no answer to the question of whether a patient is infected.

But similar PCR tests for other viruses do offer some sense of how contagious an infected patient may be: The results may include a rough estimate of the amount of virus in the patient’s body.

“We’ve been using one type of data for everything, and that is just plus or minus — that’s all,” Dr. Mina said. “We’re using that for clinical diagnostics, for public health, for policy decision-making.”



But yes-no isn’t good enough, he added. It’s the amount of virus that should dictate the infected patient’s next steps. “It’s really irresponsible, I think, to forgo the recognition that this is a quantitative issue,” Dr. Mina said.


The PCR test amplifies genetic matter from the virus in cycles; the fewer cycles required, the greater the amount of virus, or viral load, in the sample. The greater the viral load, the more likely the patient is to be contagious.

This number of amplification cycles needed to find the virus, called the cycle threshold, is never included in the results sent to doctors and coronavirus patients, although it could tell them how infectious the patients are.

In three sets of testing data that include cycle thresholds, compiled by officials in Massachusetts, New York and Nevada, up to 90 percent of people testing positive carried barely any virus, a review by The Times found.

On Thursday, the United States recorded 45,604 new coronavirus cases, according to a database maintained by The Times. If the rates of contagiousness in Massachusetts and New York were to apply nationwide, then perhaps only 4,500 of those people may actually need to isolate and submit to contact tracing.


One solution would be to adjust the cycle threshold used now to decide that a patient is infected. Most tests set the limit at 40, a few at 37. This means that you are positive for the coronavirus if the test process required up to 40 cycles, or 37, to detect the virus.

Tests with thresholds so high may detect not just live virus but also genetic fragments, leftovers from infection that pose no particular risk — akin to finding a hair in a room long after a person has left, Dr. Mina said.

Any test with a cycle threshold above 35 is too sensitive, agreed Juliet Morrison, a virologist at the University of California, Riverside. “I’m shocked that people would think that 40 could represent a positive,” she said.

A more reasonable cutoff would be 30 to 35, she added. Dr. Mina said he would set the figure at 30, or even less. Those changes would mean the amount of genetic material in a patient’s sample would have to be 100-fold to 1,000-fold that of the current standard for the test to return a positive result — at least, one worth acting on.


“It’s just kind of mind-blowing to me that people are not recording the C.T. values from all these tests, that they’re just returning a positive or a negative,” one virologist said.Credit…Erin Schaff/The New York Times

The Food and Drug Administration said in an emailed statement that it does not specify the cycle threshold ranges used to determine who is positive, and that “commercial manufacturers and laboratories set their own.”


The Centers for Disease Control and Prevention said it is examining the use of cycle threshold measures “for policy decisions.” The agency said it would need to collaborate with the F.D.A. and with device manufacturers to ensure the measures “can be used properly and with assurance that we know what they mean.”

The C.D.C.’s own calculations suggest that it is extremely difficult to detect any live virus in a sample above a threshold of 33 cycles. Officials at some state labs said the C.D.C. had not asked them to note threshold values or to share them with contact-tracing organizations.

For example, North Carolina’s state lab uses the Thermo Fisher coronavirus test, which automatically classifies results based on a cutoff of 37 cycles. A spokeswoman for the lab said testers did not have access to the precise numbers.

This amounts to an enormous missed opportunity to learn more about the disease, some experts said.

“It’s just kind of mind-blowing to me that people are not recording the C.T. values from all these tests — that they’re just returning a positive or a negative,” said Angela Rasmussen, a virologist at Columbia University in New York.


“It would be useful information to know if somebody’s positive, whether they have a high viral load or a low viral load,” she added.

Officials at the Wadsworth Center, New York’s state lab, have access to C.T. values from tests they have processed, and analyzed their numbers at The Times’s request. In July, the lab identified 872 positive tests, based on a threshold of 40 cycles.

With a cutoff of 35, about 43 percent of those tests would no longer qualify as positive. About 63 percent would no longer be judged positive if the cycles were limited to 30.

In Massachusetts, from 85 to 90 percent of people who tested positive in July with a cycle threshold of 40 would have been deemed negative if the threshold were 30 cycles, Dr. Mina said. “I would say that none of those people should be contact-traced, not one,” he said.

Other experts informed of these numbers were stunned.

“I’m really shocked that it could be that high — the proportion of people with high C.T. value results,” said Dr. Ashish Jha, director of the Harvard Global Health Institute. “Boy, does it really change the way we need to be thinking about testing.”


Dr. Jha said he had thought of the PCR test as a problem because it cannot scale to the volume, frequency or speed of tests needed. “But what I am realizing is that a really substantial part of the problem is that we’re not even testing the people who we need to be testing,” he said.

The number of people with positive results who aren’t infectious is particularly concerning, said Scott Becker, executive director of the Association of Public Health Laboratories. “That worries me a lot, just because it’s so high,” he said, adding that the organization intended to meet with Dr. Mina to discuss the issue….

I remember when I went to the hospital for an appendectomy, I was tested Covid negative when I entered the hospital and just before surgery, I was tested again and it came out positive. For two days I was put in an isolated Covid ward and I could have no visitors.

This is an old article and it's misleadingly used by Covid denialists.

The test needs you to have enough of a viral load for reliable detection. So the false tests would tend to be false negatives, not false positives. False positives would be rare since if you test positive, you would be pretty much guaranteed to have the virus if the test is done properly.


Thing is too OP, if these were really false positives, that means Covid is actually now a much deadlier disease since the fatality rate is now a bigger proportion of the actual cases. If 90% are false positives that means that Covid has a fatality rate similar to a much deadlier disease, like smallpox. And that is assuming it is treated, so untreated Covid would be even more dangerous.

That would actually justify the very aggressive responses towards Covid that were taken.


Obviously BS, but it shows the implications of 90% false positive tests (article in OP is full of fuk).

Uhh millions of people died, bro. LMFAO. The only scam was you dumbasses being scammed out of protecting yourselves.

Try to understand the argument. If there were a huge number of false positives and still that many excess deaths, it would mean covid was far more fatal. We have excess death data and also, when people die from covid, they die in stereotypical ways.

Try to understand the argument. If there were a huge number of false positives and still that many excess deaths, it would mean covid was far more fatal. We have excess death data and also, when people die from covid, they die in stereotypical ways.

It's basic math…Do I need to explain it?

Ok I will try to reduce it to your level.

Hurr durr. Fraction have number up top and number below. If make number below smaller, that make fraction bigger. Hurr durr.

When basic arithmetic is considered so elite as to be hubris, we have truly failed as a civilization. Wow.

When basic arithmetic is considered so elite as to be hubris, we have truly failed as a civilization. Wow.

We've already established you are retarded so let me explain again.

fatility rate = # of dead/# of infected. Now, we know a certain number of excess deaths happened from covid. But if the false positives are super high, and we overestimated the number infected, then that reduces the denominator, thereby making the FATALITY rate BIGGER.

Not overconfidence, just plain fuking arithmetic. Dipchit.

Excess deaths. Try to keep up. Something else? Like what, retard? You can't argue vaccines because we saw the excess deaths long before the vaccines came out. What was it? The jews?

Yes, I am sure your CrItIcAl ThInKiNg is on full display here. Go ahead and publish your stunning revelations about covid.

Excess deaths. Try to keep up. Something else? Like what, retard? You can't argue vaccines because we saw the excess deaths long before the vaccines came out. What was it? The jews?

Yes, I am sure your CrItIcAl ThInKiNg is on full display here. Go ahead and publish your stunning revelations about covid.

Excess deaths. Try to keep up. Something else? Like what, retard? You can't argue vaccines because we saw the excess deaths long before the vaccines came out. What was it? The jews?

Yes, I am sure your CrItIcAl ThInKiNg is on full display here. Go ahead and publish your stunning revelations about covid.

Pretty sure he’s Jewish lol

I remember when I went to the hospital for an appendectomy, I was tested Covid negative when I entered the hospital and just before surgery, I was tested again and it came out positive. For two days I was put in an isolated Covid ward and I could have no visitors.

I don't care if you're jewish. What do you want? A medal? Go suck some baby dick or genocide some Palestinian kids then.

It is also well known that tons of people did actually die to the fuking virus. It's a total mindfuk that you meatheads think you understand epidemiology better than people who do this chit for a living. Take the baby dick out of your mouth, and try going to college and actually passing a few classes before you open your uneducated trap.

Correct, people did die from the virus, but not as many as you think because you possess a weak and feeble mind, unfortunately. Also, my information is coming from world-class physicians. Sounds like YOU are the uneducated dumbass who has zero comprehension of epidemiology here.

FFS OP, a small amount of something is not nothing.
If a doctor told you had cancer, but only a little bit, so basically didn't have cancer and could just go home, would you buy that?
Actually you probably would. If you even believe in cancer this week.

The test needs you to have enough of a viral load for reliable detection. So the false tests would tend to be false negatives, not false positives. False positives would be rare since if you test positive, you would be pretty much guaranteed to have the virus if the test is done properly.

FFS OP, a small amount of something is not nothing.
If a doctor told you had cancer, but only a little bit, so basically didn't have cancer and could just go home, would you buy that?
Actually you probably would. If you even believe in cancer this week.