Thinking About Health: What you need to know about coronavirus testing

Testing! Testing! Testing! That’s what the experts said is necessary to move the country back to normalcy. Almost daily, local TV stations in New York City where I live run public service announcements urging viewers to get a test for COVID-19. Those announcements tell how to find a testing site, and most point out that the tests are free.

Many New Yorkers, as well as people in other states, are undoubtedly confused about the kinds of tests available, wonder about the delays in getting results and worry about the tests’ reliability. The recent experience of Gov. Mike DeWine of Ohio, who first tested positive for the virus and then negative on subsequent tests, illustrates the potential problems with the tests’ accuracy.

To sort all this confusion out, I contacted Teresa Carr, an independent health and science journalist I had worked with at Consumer Reports who had just written “A Consumer’s Guide to Getting Tested for the Coronavirus.”

The place to begin, she said, is to distinguish between the two types of tests currently available, which people often confuse because the talking heads on television don’t always make clear which they are talking about. Some tests are diagnostic and tell you whether you have an active viral infection that may require treatment or a quarantine. Others are antibody tests.

Antibody tests, which are not diagnostic tools, reveal whether a person’s blood contains antibodies that can show that they were infected by the virus in the past.

“These tests can’t tell you if you’re contagious or if the antibodies will cause you to be immune to future infections,” Carr said. “This disease has only been around since February, and we have to do more research.”

She explained that some people have COVID-19 symptoms for a long time. They may go on for months and wax and wane. In those cases, are people exhibiting a long course of the same infection or several separate infections?

“It’s really not clear what the antibody tests mean at this point,” Carr said.

Antibody tests are blood tests, unlike the more meaningful diagnostic tests that are recommended as an important way to fight the disease. Since the virus attacks the respiratory system, diagnostic tests – so called PCR tests – hunt for the virus that may be present in your nose and throat. A health care worker collects a sample by inserting a 6-inch swab through a nostril and obtaining some cells from the upper part of your throat.

Another, simpler test is less invasive. The swab reaches only an inch or so inside the nose and is more comfortable for the patient. Experts now believe the simpler test may work almost as well, but health care workers giving the test may also swab the back of your throat to obtain a more robust sample. 

Carr told me that the Food and Drug Administration has now authorized do-it-yourself tests.

“It’s a shallower nasal swab test ‘but not quite as accurate.’ Another test requires users to spit in a test tube and send it to the lab. Both these kinds of tests are ‘probably pretty good,’” Carr said, and they have been useful in places where testing materials have been in short supply.

DeWine said that the first test he took, which gave a false positive result, was an antigen test. His later tests were PCR tests that, as I’ve explained, examine virus cells taken from a patient’s nasal passages. DeWine called the PCR test “very, very, very reliable,” and added, “People should not take away from my experience that testing is not reliable or doesn’t really work.”

In fact, testing and contact tracing, the practice of following up with people who have been in contact with a person who has tested positive for the disease, are major defenses against the spread of the virus. People identified through contact tracing are advised to self-isolate or get tested themselves.

Carr told me that the length of time people wait to get their test results “varies quite a lot” with some people waiting as long as two weeks to find out if they have the disease. In general, though, you can expect a test result within a week. But if you think you have COVID-19, “you really need to be quarantining the whole time” you are waiting for results.

Carr had a last piece of advice: “Nobody should have to pay for their tests.”

Under new laws passed this spring, COVID-19 testing is now free with no cost sharing. Congress has made it possible for those without insurance to get free tests through their state Medicaid programs. Check with your state since a few states have not yet adopted that policy.

What has been your experience with testing? Write to Trudy at [email protected].