When COVID-19 spread throughout the world, countries immediately ordered testing on their citizens to assess how much the virus had spread. Testing has become a crucial part of the pandemic but experts said that test results are not always 100% accurate.
False negatives can also happen wherein you get a negative result when you should have tested positive. People who get a false positive could become silent spreaders that is why following health protocols are still important.
Here are some reasons why having a negative test result does not 100% guarantee that a person is not infected by COVID-19.
Different Tests Have Varying Degrees of Accuracy
COVID-19 testing in the US has ramped significantly over the past few months. Health workers either use the polymerase chain reaction tests (PCR), considered as the gold standard; or the less accurate antigen tests.
PCR tests are processed inside a laboratory while the antigen test is faster and cheaper which detects the protein surface of the virus. Most of the rapid tests are estimated to be 90% accurate. Between the two options, the PCR test gives a more reliable test result although the results might take longer to arrive, The Washington Post reported.
However, this does not necessarily mean that they will never yield a negative COVID-19 result because they are also prone to false negatives. That could be due in part that the cotton swabs may not pick up all traces of the virus or that it has moved to the lungs from the nose, or perhaps the swab may not have been inserted far enough.
Nonetheless, they are still more reliable than the non-invasive COVID-19 test.
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COVID-19 Test May Not Be Able to Detect the Virus Early In An Infection
The Seattle Times noted a report from the Post that some COVID-19 tests could not detect the novel coronavirus early in an infection. According to the Annals of Internal Medicine, when using a PCR test on the day of the exposure, the false negative is 100%, but it gets down to 38% five days later as symptoms start to appear.
Infectious diseases and medical virology lecturer Muge Cevik of the University of St. Andrews said that it is still unclear when a person who tested positive with COVID-19 will show a positive test, so false negatives could happen. That means they could still be contagious.
People exposed to COVID-19 and tested negative should be tested again in a few days and self-quarantine while waiting for the results to prevent transmitting the virus to other people.
You Could Get Infected After Testing Negative COVID-19 Test
According to BGR, a person who had just tested negative for COVID-19 could get infected after the test. That means the test you took now would not mean anything if you get infected with COVID-19 after the test.
Theoretically speaking, the Post reported that anyone could get infected ten minutes after taking the test as they go out to public places, like the market. This factor is important to keep in mind so that people would be aware of the possibility that anyone they meet could be positive for the virus.
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