COVID-19 testing has been an integral part of our country’s strategy to limit disease transmission. Here’s the latest information on types of tests, when they’re appropriate to use, and what they realistically can and cannot do to curb infection.
While testing for COVID-19 has been available in some form since shortly after the pandemic began in early 2020, uneven access to tests and questions about the accuracy of different tests has persisted. Aiming to offer some clarity around who needs COVID-19 testing and when, the Infectious Diseases Society of America (IDSA) recently held a media briefing to address the topic.
Technically, anyone who wants a test can walk into a pharmacy or healthcare office and get one, but challenges remain. “We know that molecular testing has the highest sensitivity for ruling out--for excluding—COVID,” said Nira Pollock, MD, PhD, an IDSA member and associate medical director, Infectious Diseases Diagnostic Laboratory, Boston Children's Hospital. “But we still have issues with access, with turnaround time, with cost, and with supplies facing both patients and laboratories.” Even as testing has evolved, long lines at healthcare facilities may persist, Pollock said. It may be hard to get an appointment at a pharmacy, and fewer state testing sites remain open. Supply chain problems mean testing supplies are not always abundant. Samples may be sent to labs that have long turnaround times. And while the tests themselves are free to consumers, office visits may entail copays.
Home testing offers many more conveniences with a potential pitfall: the possibility of a less accurate result. “Most of the available home tests are...antigen rapid diagnostic tests, or RDTs, and those have significant potential advantages,” Pollock said. These include fast turnaround time and lower costs, at least to third-party providers. Because home tests are relatively cheap and fast, they can be used for serial testing, although there is no consensus on the optimal interval between tests. However, the ability of rapid tests to detect the virus is somewhat reduced compared with that of PCR tests. “There’s still disagreement about whether a negative RDT can effectively rule out infection in a symptomatic individual,” Pollock noted, adding that a person can have a negative antigen test and positive PCR test and be infectious.
One problem with home tests is that people might administer them incorrectly, which could affect results. Another issue is that positive results may not be reported. “I think we will probably lose track,” said Dial Hewlett Jr., MD, FIDSA, an IDSA Fellow and medical director, Division of Disease Control, Westchester County Department of Health in New York. “We won’t have as accurate an idea in terms of what the prevalence of the disease is at any given time. On the other hand, I think that having access to these results in a very rapid way will be helpful in terms of the practical issues of going to school.”
Rapid testing may indeed be the key to keeping kids in school, although there are obstacles.
No agreed-upon definition exists that spells out exactly which symptoms trigger the need for a test. There also is no consensus about the need for school testing if transmission rates in an area are low. Pollock mentioned the “Test and Stay” program being piloted in certain districts by the Centers for Disease and Control (CDC), which involves regular rapid onsite testing and contract tracing of potentially exposed children and staff so they don’t have to quarantine at home.
While PCR tests catch more positive results than do rapid tests, the lag time between testing and results can be as long as several days. This can be problematic if people don’t quarantine while waiting for results. Hewlett explained that under the vaccine mandate for healthcare workers, those in his county who receive exemptions must take molecular tests once a week. “The shortcoming o[f] this is that an individual may test negative on Monday and then they may actually start to develop symptoms on Tuesday,” he said. Meanwhile, coworkers are potentially exposed during that time.
For vaccinated but asymptomatic individuals, when and whether to test is more of a nuanced discussion. If a group is planning to gather for the holidays and all are vaccinated, should they all take Covid-19 tests beforehand? The answer depends on whether anyone is vulnerable due to age or comorbidities, the experts agreed. “[T]esting in vaccinated people really is a balance of risk--risk for those around you, risk for yourself and your health history, and also access and resources,” Pollock said. Hewlett said that if the gathering includes, for example, someone with Stage 4 cancer, it would be appropriate for all attendees to test before coming together.
The panel’s experts lamented that finances might factor into someone’s decision to get a COVID-19 test. While tests administered at an urgent care center or lab are free to the consumer, reports of third-party bills sent to insurance companies or the government are not unheard of. And rapid tests for home use can start at $25 for a 2-pack and run to $35 or more, which may be out of reach for many families, especially those with multiple children. “The fact that someone with means can more quickly get a test to exclude COVID in their child and get that child back to school than potentially someone without those resources--it just shouldn't be that way,” Pollock said.
Pollock added that it has been difficult to find rapid tests of late, although the Biden administration has invested heavily in their development and availability, which should make them easier to obtain heading into the winter season.