WENATCHEE — Confluence Health on Wednesday will begin using COVID-19 antigen tests, a new method that can return results to patients within a day.
Rather than being sent to an external lab for processing, which can take several days, these tests will be analyzed in Confluence Health facilities, Chief Medical Officer-elect Dr. Jason Lake said Tuesday.
Each test can be analyzed in around 15 minutes. Patients who are tested in the morning could expect to receive their results the same day and people tested in the afternoon would likely receive results the following morning, he said.
Nearly all health care organizations in the area, including Confluence Health, have been using a testing method called polymerase chain reaction, or PCR. These tests amplify and detect genetic material associated with the virus — which is highly accurate but takes a full lab and more time to conduct.
Antigen tests look for fragments of the virus’ protein, a process that’s faster but can also be less accurate, according to the Centers for Disease Control and Prevention.
Confluence Health is using an antigen testing system from a company called Quidel Corporation, which received authorization for emergency use of the tests from the Food and Drug Administration in May. Confluence is confident the tests will perform accurately, Lake said.
“The problem with antigen tests as a whole category is there’s a lot of variability in the accuracy of the tests, dependent on the maker of the device and the reagent,” he said. “Different antigen tests have different characteristics. The test that we have … is a very, very good, highly reliable antigen test. It’s probably the best antigen test machine out there. So it has a sensitivity nearly 97% compared with PCR.”
Since antigen tests are not as sensitive as PCR tests, positive results are “highly accurate” but the tests can’t always detect lower traces of the virus, which can lead to false negatives, read part of an FDA release.
Confluence will still use traditional PCR tests in situations where accuracy is critical.
If a patient is admitted to Confluence’s Central Washington Hospital with respiratory infection symptoms similar to COVID-19 and an antigen test returns negative, a follow-up PCR test will be used to confirm the results.
“If they get a negative antigen test, we’re going to send a PCR just to be absolutely sure,” Lake said. “What we want to do is make sure our PPE practices continue to be robust in the hospital to keep patients and staff safe. So we really don’t want to miss any possible COVID cases for patients coming into the hospital.”
Starting Wednesday, the “vast majority” of tests performed by Confluence Health will use the antigen method, including at its drive-thru sites, Lake said. In early August the main drive-thru in Wenatchee was testing around 400 people per day.
Lake wasn’t aware of any other health care providers in North Central Washington that have wholesale switched to antigen tests. But Confluence Health spoke with the Department of Health, which was “very comfortable” with the change, he said.
It’s been stocking up on supplies in anticipation of the changeover and now has a little over 7,000 antigen tests on hand.
Confluence’s PCR swabs needed to be inserted deep into the nose to collect an optimal sample. In addition to a faster turnaround time, the new antigen tests only require a shallow swab in the nose.
“At the same time we’re converting to nasal swabbing that the patient can do themselves, rather than the nasopharyngeal swabbing, which is more invasive and more uncomfortable,” he said. “So we think that this will be a much more comfortable test for the patients as well. So there’s a lot of reasons we’re excited about making this conversion.”
They’ll be processed with the same machines the organization uses for analyzing traditional flu tests, Lake said.
“I think this sets us up very well in terms of workflows as we approach the flu season,” he said. “For patients who have respiratory symptoms, they ultimately may need to be tested for the flu and for COVID as we enter into the fall, and we consolidate that testing all into the same machine.”