Dr. Roger Hicks: What’s the story with COVID testing?
Most everyone understands that COVID is not just another flu. Things happen with COVID that do not happen with the flu, like cytokine storms, a life-threatening over-reaction of the immune system; blood clotting abnormalities, strokes, and heart attacks in young adults; and multisystem inflammatory syndrome in children.
Many people have had the flu or the vaccine so there is pre-existing community immunity to it, and there are antiviral treatments that are effective if taken early in the illness. None of these exist for COVID-19. Right now, the only defense we have is to control the spread of the virus. Controlling the virus takes our whole community — our entire nation, really — to commit to wearing face coverings in public, social distancing, frequent handwashing and testing.
Let’s talk about testing
There are two kinds of COVID-19 tests: those that detect the SARS-CoV2 virus (viral tests) and those that detect antibodies to it (antibody tests).
The antibody tests, also called serology, are blood tests that detect IgG and IgM antibodies we create in response to infections. Antibodies appear about two weeks after an infection starts, so these tests are not at all useful for diagnosing active infections. Furthermore, none of the serology tests available today under the FDA’s Emergency Use Authorization has been fully vetted. Serology tests may tell us if we have been exposed to a form of the SARS virus in the past, but not if we have enough, or the right kind of antibodies to make us immune to a second round. Serology tests are useful for public health purposes, enabling us to estimate how many people have had the infection and adding to the body of knowledge we are building about the virus.
The viral tests are different. They use a swab specimen to look for viral fragments and are designed to identify active infections. Right now, there are two types of viral tests for COVID.
The first type of viral test is the polymerase chain reaction (PCR) molecular analysis. PCR tests that are sent to a reference lab, such as Quest or Labcorp, are the most accurate and considered the gold standard… for now. They detect viral RNA and use a swab from the front, middle or back of the nose; or from the throat; depending on the testing protocol. The back of the nose or nasopharyngeal technique is the most accurate and uses a very thin Q-Tip-like swab that is inserted deep into the nasal cavity. This is uncomfortable, but NOT a “painful” process as some have described, and test collection goes very quickly.
The second type of viral test is antigen tests which detect viral protein in an actively infected person. Intended for people with symptoms, these rapid tests use nasal swabs analyzed by an in-office machine that produces results in 15-30 minutes. They are very sensitive, meaning if the test is positive, it is highly likely you have the infection, but if it is negative, there is some uncertainty. They have a false negative rate of 12.5 – 20%, so a PCR test should be done on every negative antigen test for confirmation. The PCR test can be sent off during the same office visit.
The CDC recommends testing for anyone with 15 minutes or more of close contact to a person with confirmed COVID-19. The CDC defines close contact as being “within 6 feet of an infected person for at least 15 minutes starting from two days before illness onset (or, for asymptomatic patients, two days prior to specimen collection).
If you are exposed to COVID it takes several days for the virus to multiply enough in your body to be detectable by one of the tests. Therefore, wait at least three days from your exposure to be tested.
Viral tests are like a snapshot in time. A negative result means at the moment the test was done you didn’t have COVID, but you could get it in the future … even the next day … while waiting for your test results.
Countries that have been most successful in controlling the spread of the infection, such as South Korea, Taiwan, Japan, Thailand, Iceland and countries in the European Union, all have widespread viral testing. Testing helps keep workplaces safe. Public health workers can then do contact tracing: identifying people who have been with the infected person. When negative, the viral tests help avoid unnecessary quarantine and missed work.
Despite what some politicians say, the US does not do the most testing per capita of any country in the world. Less than 3% of us have been tested so far. Our country has 5% of the world population but 25% of the COVID cases and deaths. While the number of new cases is low in other developed nations, we have more than any other country in the world. Why have we been unable to effectively deal with the pandemic?
Part of the reason is testing got off to a slow and rocky start in the U.S. Although there are still many areas where testing is not widely available, that is not the situation in Nevada County. Tests are available at several sites, including our local urgent care facilities. Testing is also available by appointment through OptumServe at the Grass Valley Veterans Hall. Call 1-800-634-1123 during business hours or visit https://lhi.care/covidtesting.
California’s reopening criteria require a certain baseline of testing occurring in the community. If we fall below that level, it could impair our ability to detect and trace the infection locally and could result in our slowing down or even reversing our reopening. So do your part — get tested. And please stay in place, keep your space, and cover your face.
Dr. Roger Hicks is the Medical Director for Yubadocs Urgent Care in Grass Valley and the founding president and current Director of the California Urgent Care Association.
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