A new study has found that the chance of getting a false negative after a quick antigen Covid test results in less than 0.1% of all tests.

The University of Toronto in Canada collected data from various workplace testing programs to find out how frequently people who are not carrying the virus might test positive.

While functional antigen tests may be more accurate than PCR tests that are deemed ‘gold standards’, they can still not provide as much information. However, a PCR result can take up to days while antigen testing results may be available in just 15 minutes. 

Rapid tests are popular for school and workplace testing. They can also be used for people who have asymptomatic conditions and want to check before traveling or for major events.  

False positives can have severe consequences for businesses, leaving them without staff or forcing individuals to cancel major travel plans or skip important events due to the virus.

A Canadian research team found that only 0.05% of rapid antigen Covid tests are false positives, and even the ones the found may be a result of a very specific batch of faulty tests that were distributed in one part of the country during the fall. The low likelihood of false positives is a promising sign for workplaces and schools that regularly use the tests. Pictured: A man in Washington D.C. is tested for COVID-19 on January 13

Canadian researchers discovered that only 0.5% of rapid Antigen Covid Tests are false Positives. This is in contrast to the 0.05% that have been found. However, the ones that did not prove positive may just be the result of one batch of defective tests distributed in an area of the nation during fall. For schools and workplaces that use these tests regularly, the low chance of false positives can be a good sign. Pictured: This is a Washington D.C. man who was tested for COVID-19 in January 2013.

The overall false-positive rate for all rapid antigen screenings. [COVID-19]It was quite low, which is consistent with other smaller studies,” researchers stated. 

The findings of the researchers were published in JAMA.

The testing period covered the final parts of Omicron’s last winter’s Covid surge (the largest that the nation has ever suffered before Omicron arrived) and two distinct surges from the Delta variant. 

One hundred and thirteen (or 0.15%) of the tests returned positive results.

People who tested positive for these programs were then given a PCR test and results within a few days.

A false positive is a test that shows a person has had a positive test for antigens but was later negative by PCR.

There were 462 PCR results that came back negative. This means that a third (or more) of the positive antigen test results were false positives. However, only 0.05% of all tested resulted with a false positivity.

Many false positives could also be caused by faulty tests that were distributed to a specific area in a given time frame.

Research showed that 60% of false positives were caused by two workplaces located around 400 miles from one another between September 25th and October 8th. 

These two companies could have received flawed batches of test results from a local distributor. This may have led to false positives. 

Researchers concluded that the false-positive clusters in one batch were likely to be due to manufacturing errors rather than problems with implementation.

Researchers believe false positives are rare, but they are possible. This is why robust PCR testing systems are essential to rapidly screen for positive rapid tests to determine which ones are correct and to identify those that are incorrect.

“The results show the importance to having a detailed data system to rapidly identify possible issues,” they said.

“With batch identification being possible within 24 hours workers can return to work. Problem batches may be discarded and public health officials and manufacturers could be informed.

The data used in this study were from prior to the Omicron variant’s rise, although officials warn that it is easier to detect with some quick tests. 

In the United States, it is difficult to get quick results from PCR tests. In the US, the Omicron variation has risen in demand.

It meant some people had to wait for results for days and sometimes even weeks. 

A person having to wait a week to return to work after a false positive  antigen test can be devastating not only to individuals, but to society as a whole.

As a result of some work shortages (either caused by fake positives or real infections), the Centers for Disease Control and Prevention lowered the maximum quarantine time for symptomsatic infection from seven to five days.