The rapid home test is negative, but do you still have coronavirus?

In the omicron era where the COVID attack rate summit From the previous variants, entire families and groups of friends get sick. If the person Corona virus diseaseThere is something good The chance of infecting others in their homes, too.

However, the strange thing is that sometimes only one or two people in a group of friends or family unit are tested positive in the rapid test. The rest, despite their symptoms, came back negative. Are rapid tests missing for infection more now than in previous variants?

Despite anecdotal evidence, the latest research suggests that combos work just as well on omicron as they do on delta (which means they can pick them up) 80% of cases confirmed by a positive PCR test).

“Overall, the rapid tests seem to work on par with omicron, as well as other variants,” Wilbur LamProfessor of Pediatrics and Biomedical Engineering at Emory University and investigator He has evaluated diagnostic tests for COVID for the federal government, according to HuffPost.

Rapid antigen tests are designed to detect a specific version of the virus. With the emergence of variants, scientists wondered whether the new mutations could affect the ability of rapid tests to detect the virus variant – but this was not the case.

the majority Instructs It is suggested that rapid antigen tests work just as well with Omicron as they do with earlier variants such as delta and alpha. One Arabic study from UMass Chan Medical School found that rapid tests detected 92% of umicron infections and 82% of delta infections that were confirmed by a positive PCR test.

There isn’t a lot of research on how tests collide with omicron sub-variables like the BA.2 variant is now prevalent, but Nathaniel HooverDr.. D., the assistant professor of molecular medicine at UMass Chan School of Medicine who worked on the UMass study, isn’t too concerned.

“I think these tests can still detect BA.2,” he said. BA.2 is a smaller variant of the omicron and variants have been consistently detected by rapid antigen tests all along, largely because the piece of virus those tests are looking for hasn’t changed much, according to Hafer.

However, rapid home tests are not foolproof, and there have been enough anecdotes to show that it has missed a percentage of cases. Scientists have some theories as to why this happens.

First, it is to increase the transmissibility of the omicron and its sub-variables (such as Bachelor 2). These variants spread so quickly that many people test themselves very early on, before the virus has had a chance to multiply in the body.

“Actually, there may not be a high enough concentration [of virus] in the nose until it hangs “, Lam said.

Another theory: Omicron is more present in the throat than in the nose. During the heyday of the omicron wave, many people shared their experiences on Twitter about how they did it. Tested positive by throat swab After the nasal swabs gave negative results. But, Anne WillieA microbiologist at the Yale School of Public Health, we don’t have an accurate estimate for this Food and Drug Administration Oral swabs rapid antigen tests are not authorized.

“This is where omicron is first discovered, which is why people keep testing negative results for days with nasal swabs. [are] Willie said. But studies I’ve looked into this specifically and found that omicrons are everywhere – throat, nose, saliva – and mouth swabs, while helpful, are no better than nasal swabs.

Some scientists believe that vaccination can reduce the viral load in the nasal cavities of some people. Essentially, your immune systems can fight off the virus and prevent it from multiplying – rapid tests need a high viral load to produce a positive test; Therefore, if there is not enough virus, the test group will not detect it. Lamm and his research team are actively studying how vaccination status, timing of vaccination and boosters affect viral load and test sensitivity, but the results have not yet been made public.

“We think it could be someone who was recently stimulated to have lower sensitivity – but that’s still our hypothesis,” Lamm said.

Everyone’s immune systems are slightly different. Some people’s immune systems may simply react and prevent the virus from replicating more successfully than others. Also, asymptomatic people tend to have higher viral loads, which are more detectable in a rapid antigen test, compared to asymptomatic people, who usually have lower viral loads.

“People with higher viral loads in the nasal and head cavities will definitely be more positive on the antigen test,” Haver said.

There’s always a chance that people can have symptoms, too, Haver added, for a variety of reasons — seasonal allergies and other common respiratory viruses come back and spread.

Finally, human error is likely. Some may not scan deeply or often enough, which may affect the amount of virus the swab picks up.

Tests also work best with tests or serial tests over several days. This gives the viral load the opportunity to increase and reach levels that can be detected in a quick test, Lamm said. On average, PCR tests – the most sensitive – show positive results two days earlier than the rapid tests.

So, while you may get a negative result the first day you show symptoms, there is a much higher chance that your rapid test will become positive two days later when your viral load is at its highest.

Experts are still learning about COVID-19. The information in this story is what was known or available in the publication, but the guidance may change as scientists learn more about the virus. Please Check out the Centers for Disease Control and Prevention For the latest recommendations.