People with coronaviruses infections of the Omicron variant often have significantly different viral levels in their noses, throats and saliva, and testing just a single type of sample is likely to miss a large share of infections.
According to the papers, coronaviruses tests that analyze both throat and nose samples would pick up more Omicron infections than tests that only use a nose sample. The combined tests are common in other countries, but not in the US.
The senior author of both papers said that you could get a lot more bang for your buck if you used mixed specimen types. He said that we are stuck with no one doing it in the US.
The data collected during the Los Angeles area study was used to create the two papers. More than 200 people from 56 households took part in the event.
Each participant had to collect a saliva sample and a nose and throat sample over the course of two weeks. The researchers used P.C.R. testing to calculate the viral load.
Fourteen people who joined the study before or at the same time that their infections began are the focus of the first paper.
The scientists were able to compare the amount of virus in different samples and people at different times with the help of this group of participants.
Different sample types from the same individuals had different viral loads.
The virus could be detected in saliva or throat swabs before it could be detected in the nose. Alexander Viloria Winnett is a graduate student at Caltech and an author of the paper.
The Caltech team conducted a study in late 2020 and early 2021. The feature doesn't seem to be specific to Omicron.
When the viral load spiked in the nose, it rose to higher levels than in either of the oral samples, according to the researchers.
There was a lot of variability even then. One woman had high levels of virus in her throat and nose throughout her illness, while the levels of the virus in her nose fluctuated between positive and negative over a week. One participant had higher viral loads in his nose than in his throat or saliva, even when he was sick.
The data shows that no single specimen type will catch more than 90 percent of infections, even with a highly sensitive P.C.R. test.
The author of the study said that focusing on a single sample type meant missing out on a large portion of the picture.
The patterns in the viral loads in the throat and nose samples were very different from the other samples. The data suggests that testing both of the sites at the same time would detect more infections than either alone.
In the second paper, the researchers looked at the performance of the test in a group of people who had started the study early on. The participants provided daily nose, throat, and saliva samples.
The scientists warned that it is possible that some tests may not work in the throat. They urged companies and regulators to pay more attention to this research.
The study administrator, who is also an author on both papers, said that if the tests could be combined, we could catch more infections.
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