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Saliva saliva tests pile up well against the gold standard for molecular COVID-19 tests – a deep swab behind the nose – without discomfort and coughing or sneezing by the tester, updated instructions appear.
In a press release today, the Infectious Diseases Association of America (IDSA) outlined the findings of an expert panel that has reviewed the literature since the IDSA released its first guidelines in May.
The panel found that saliva tests were particularly effective if the test included instructions for coughing or clearing the throat before entering the tube, panel chair Kimberly E. Hanson, MD, MHS, said. of the University of Utah in Salt Lake City.
Throat swab alone is so effective
Using a neck swab by itself was less effective and missed more issues than the other methods, she said.
The IDSA recommends an update: A saliva test or swabs from either the middle or front face of the nose is preferable to the neck swab alone.
The combination of saliva and swabs from the front and middle of the nose and throat together “looked almost identical” to the gold-level deep swab, the panel found.
She acknowledged, however, that a number of swabs are already making supply issues challenging.
Saliva samples are challenging, Hanson said. A laboratory needs to prove that its systems can handle the sticky material. And asking a coughing patient requires more personal protective equipment (PPE) for the health professional.
Each center must make the type of sample it chooses, based on the facilities available and the location – whether in a hospital or driving activity, for example, she said.
Quick vs. routine test
Panel member Angela M. Caliendo, MD, PhD, of Brown University in Providence, Rhode Island, said the panel preferred a rapid polymerase chain response Tests (PCR) and routine, laboratory-based PCR tests over rapid isothermal testing.
The panel defined rapid tests as those for which results are available within one hour of the sample being received by the test provider. They excluded home testing for this category.
The only fast isothermal test that had enough data to make a recommendation was the ID NOW test (Abbott Labs), she noted.
Rapid PCR tests performed just as well as standard laboratory-based tests, she said, with a high sensitivity of “97% on average and very high specificity.”
But the rapid isothermal test had an average sensitivity of just 80% compared to the laboratory-based PCR test, Caliendo said, yielding a large number of false-negative results.
Test centers need to emphasize the great benefits of getting results in 15 minutes with a quick isothermal test and be able to educate advanced patients about immediate loneliness against a false negative potential, which can advanced patients sent home think the virus does not – and so the disease could spread.
And if a clinician gets a negative result with the rapid isothermal test, but with a strong suspicion that the person has COVID or lives in a high-frequency area, a back-up test with rapid PCR or work-based testing should blade administration.
“You will miss a certain percentage of people who use this rapid isothermal test,” she said.
However, Caliendo said, if the only available option is the isothermal test, “you should definitely use it because it is definitely better than not testing at all.”
On a positive note, she said, all types of testing have high specificity, so “you’re not going to see a lot of false-positive results.”
The guidance back in May did not make recommendations for rapid tests, she said, as there was insufficient data in the literature.
Caliendo noted that most of the available data for patients was symbolic, but there is some data that shows that the amount of virus in the respiratory tract is similar to people with and from without symptoms. The panel therefore expects that the performance of the various assessments would be similar to whether or not a person had symptoms.
Testing their immunity
Hanson said the original recommendation in May was to perform a molecular test for asymptomatic people waiting for a referral or waiting to start immunotherapy for cancer or autoimmune disease. Now the current guidance “makes no recommendation for or against screening” in these cases.
Hanson said the panel feels the test should be performed on patients awaiting bone marrow and hard organ transplants because of the high risks that come with it if patients have contracted the virus.
But for those with cancer or autoimmune disease, the panel decided to leave it to each physician to assess individual risk and decide whether the patient should be diagnosed.
Home Test
IDSA guidelines did not emphasize home testing because the results are so new and studies to date have included less than 200 patients. But Caliendo said they clearly perform better earlier in the disease stage – the first 5-7 days – when the virus size is higher.
Hanson and Caliendo also questioned the meaning of the new virus variant, first discovered in the United Kingdom and now spreading to other countries (including the United States). for diagnostic tests.
“So far we think with the majority of EUA-authorized tests, it is unlikely that this new variant should have a significant impact on test performance,” Hanson said.
There are differences in the spike gene, and many routine tests detect and identify SARS-CoV-2 without the spike gene so that they would not be affected, she said.
Caliendo agreed: “I think most of our tests should be in good shape.”
Hanson and Caliendo have not disclosed any material financial relationships.
Marcia Frellick is a freelance journalist based in Chicago. She has previously written for the Chicago Tribune, Science News and Nurse.com and was an editor at the Chicago Sun-Times, the Cincinnati Enquirer, and the St. Louis. Cloud (Minnesota) Times. Follow her on Twitter at @mfrellick
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