At the same time, some evidence suggests that severe illness and hospitalization may be less likely with Omicron, although those who are unvaccinated are still considered to be at greater risk from infection. The variant is believed to be more transmissible and may evade some vaccine protection compared to its predecessor, Delta. This could apply to high-risk settings such as hospitals, congregate settings and long-term care homes, as well as occupational settings.Īnd while children may not get as sick from COVID-19, confirming an antigen test with PCR would become much more important for someone such as a teacher with a medical condition, Smieja said.Ī surge in demand has led to long lineups at testing centres in certain provinces, as well as difficulties trying to find a timely appointment as cases of COVID-19 increase sharply amid the spread of the new Omicron variant. In those cases, PCR would be relied upon in order to fully understand the extent of an exposure, and in turn protect the group involved and the public at-large, he said. "If it's a hospital outbreak where antigen is the initial positive, I absolutely need to see that confirmed before I'm going to swab a lot of staff and patients on that ward," Smieja said on CTV’s Your Morning. Meanwhile, on the public health side, using PCR over antigen tests alone would be important for hospital investigations and potential outbreaks, which he says antigen tests alone won’t fully capture. In another instance, a person in their 70s may want to confirm a positive rapid test with PCR, given that age group is at a higher risk of severe illness and hospitalization due to COVID-19, Smieja said. However, if that same child is so ill they need to go to the emergency room, then a PCR test would be needed to confirm it is due to COVID-19. "By that, I mean if it's a child who's going to stay home for 10 days, I think that it may be acceptable not to confirm those by PCR,” Smieja told CTV's Your Morning.Ĭhildren are much less likely to develop severe illness from COVID-19 compared to adults, and if a child does receive a positive rapid test but doesn't feel overly sick, Smieja explained in a telephone interview with CTVNews.ca that there is little risk involved forgoing the PCR. Newsletter sign-up: Get The COVID-19 Brief sent to your inbox.While it is ideal to follow a positive rapid test result with a lab-based polymerase chain reaction test, commonly known as a PCR test, he says it would depend on how much individual risk is involved, and what the risk would be to public health. Marek Smieja, an infectious disease specialist and professor at McMaster University in Hamilton, Ont., spoke to CTV News on Wednesday about COVID-19 testing, saying it “may not be practical” to confirm some positive rapid tests, particularly for those who have had limited contacts and no symptoms. “If you live in a low prevalence area like we do, a lot of the positive antibody test results are false-positive results.” There are a few reasons for this, such as the test picking up antibodies for other types of coronaviruses.As certain provinces experience backlogs in administering and processing COVID-19 lab tests, one doctor says confirming a rapid test result with PCR may not be practical in all situations.ĭr. “That’s been one of the limitations ,” she said. Zander said.Ĭonversely, false positives are much more common with antibody tests. “Laboratories work very hard to minimize the risk of cross-contamination, so it’s not common,” Dr. It can happen in a situation where there’s cross-contamination, she said. Zander said.įalse positives are also uncommon in PCR tests. Other tests, such as a type of rapid test called an antigen test, are “less sensitive” to detecting the virus, Dr. Their viral load may also be low at the end of the course of their infection. Someone may have a very low viral load in the first couple of days after they’ve become infected. Zander said.Ī viral load represents the amount of the virus in any given testing sample, like on a nasopharyngeal swab. “A false-negative test can happen if one has a very low viral load,” Dr. The type of COVID-19 test that UC Health uses - a PCR test, which looks for genetic material of the novel coronavirus - is the gold standard test.įalse positives and false negatives, therefore, aren’t common, said Dani Zander, MD, chief of Pathology and Laboratory Medicine at UC Health.
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