A false negative is when a test incorrectly comes back as negative. False negatives can occur with any type of test, from pregnancy tests to Covid-19 tests. With something like a pregnancy test, a false negative usually isn’t too big of a deal. But with Covid-19, a false negative could have dangerous consequences.
The NIH defines a false negative as “A test result that indicates that a person does not have a specific disease or condition when the person actually does have the disease or condition” False negatives can happen with PCR tests, which are the most common type of Covid-19 test. PCR tests look for the virus’s genetic material, and they’re very accurate. But in some cases, the virus’s genetic material isn’t detectable, even though the person is infected.
There are a few reasons why this might happen. One is that the test was done too early in the infection, before there was enough viral material to detect. According to the Centers for Disease Control and Prevention (CDC) Fact Sheet for patients, “You might test negative if the sample was collected early during your infection.” Thus, it is important to get tested at the proper time post infection. The CDC states that “If you have symptoms, test immediately. If you were exposed to COVID-19 and do not have symptoms, wait at least 5 full days after your exposure before testing.” You should also take into consideration the type of testing being done. We highly recommend asymptomatic patients to choose PCR testing as it is better able to detect viral infection. False negative results can also happen if the sample wasn’t taken correctly, or if the PCR test wasn’t done properly. And in some cases, people who have been infected with Covid-19 develop immunity and no longer test positive for the virus, even though they could still transmit it to others.
Self-testing kits are another type of Covid-19 test. These usually use antigen tests, which look for proteins that are found on the surface of the virus. Rapid antigen tests are less sensitive than PCR tests, which means they’re more likely to give false negatives.
False negatives are a problem because people who think they don’t have the virus might not take the precautions they need to avoid infecting others. They might not wear a mask, or practice social distancing, or self-isolate if they develop symptoms. Given that someone tests negative but has been exposed to the virus, they might not quarantine for the recommended 14 days. There’s also a chance that someone could test negative even though they’re infected and able to transmit the virus. This is more likely to happen in the late stages of infection, when people are less symptomatic and shedding fewer viruses. It’s also more likely to happen with rapid antigen tests than PCR tests. False negatives can have serious consequences, which is why it’s important to understand how they happen and what you can do to avoid them. If you’re worried about getting a false negative, you can get tested more than once, or wait a few days after exposure to get tested. And if you test positive, make sure to isolate yourself and follow the recommended quarantine protocol.
Which type of Covid-19 testing is most likely to result in a false negative?
There are two main types of Covid-19 tests: antigen tests and PCR tests. Antigen tests are less accurate than PCR tests and are more likely to result in a false negative. This means that if you have an antigen test, you could be infected with the virus even if your test comes back negative.
PCR tests are more accurate and are the best way to detect the virus. However, PCR tests can also give false negatives, especially if they are done early on in the infection. If you think you may have been exposed to the virus, it’s important to get tested 5 days post exposure. Symptoms of Covid-19 can appear anywhere from two to 14 days after exposure. This is why it’s so important to self-isolate and get tested if you think you’ve been exposed. If you test negative, you should continue to self-isolate for 14 days from the date of exposure. Antibodies develop in the body about two weeks after infection, so a PCR test done at this time will be more accurate. However, even if your PCR test comes back negative, it’s still possible that you have the virus. This is because antibodies can take up to four weeks to develop in some people.
The bottom line is that no matter which type of test you get, there is always a chance of a false negative.
How can you prevent getting a false negative test result?
The Centers for Disease Control and Prevention (CDC) recommends that people get tested at least five days after their last possible exposure to the virus. This is because it takes time for the virus to replicate in the body and be detectable through a PCR test.
Another way to prevent a false negative is through immunity. People who have previously had a COVID-19 infection are likely to have some level of immunity due to developing Covid-19 antibodies, which can help protect them from getting infected again. Additionally, people who have been vaccinated against SARS-CoV-2 are also less likely to get infected and will have a lower risk of transmitting the virus if they do get infected. Finally, self-testing in symptomatic people can also help prevent false negatives. Antibody tests can be used to detect if someone has previously been infected with the virus and now has immunity. Additionally, antigen tests can be used to detect the virus itself. These tests are not as sensitive as PCR tests, but they can still be useful in detecting infections, especially in people who are symptomatic or have early symptoms.
Prevention is key when it comes to avoiding a false negative result. By getting tested at a reputable facility, building up immunity, and self-testing, you can help ensure that you get accurate results. False negatives can lead to missed infections and increased transmission of the virus, so it is important to do everything you can to prevent them.
In order to avoid the risks of a false negative Covid-19 test result, patients can perform a repeat at home or get retested at a facility in order to confirm the test results and avoid the consequences related to a false negative. The FDA recommends that patients get tested again after 48 hours of getting a negative test result. Patients who have symptoms and suspect they may be infected even after a negative test, should get tested a second time 48 hours post results.
Asymptomatic patients who suspect they may be infected even after the second negative test, should get tested a third time after 48 hours of getting negative results.
False negatives are just one of the many challenges we face with Covid-19 testing. But by understanding how they happen, we can take steps to avoid them and keep ourselves and our communities safe. Retesting can help prevent the consequences of false positives and negatives. As recommended by the FDA, retesting according to FDA guidelines would be beneficial to yourself and others around you.
Do you have any questions about false negatives? Leave us a comment below! And be sure to check out our other blog posts about Covid-19 testing for more information.
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