COVID-19 is a tough challenger, in part, because it’s an invisible virus. Some people have minimal to no symptoms, or assume they’re just suffering from allergies or a cold, yet they shed the virus and spread it around our community. Others end up so desperately sick they require critical care and may even die. Fighting an enemy like this is complex.
Since COVID-19 hides, the way to see it is through testing. Positive results must be followed up with contact tracing and isolation. Timely and accurate testing facilitates clinical care decisions in real time. Test results inform important decisions for our hospitals and clinics and provide critical information for local, state and federal leaders to best understand the pandemic and design mitigating strategies to slow or control it.
Conversations and questions about testing are swirling. It’s confusing and frustrating to not know what’s accurate or the right thing to do. During a novel pandemic, testing evolves with the disease. So, what are the different types of testing, who gets tested and what does it mean?
Here’s what we know today:
Clinical testing is used for diagnosis and to help develop an appropriate plan for treatment and care. Polymerase chain-reaction (PCR) or molecular-based testing basically looks for genetic material and identifies whether the virus that causes COVID-19 is present. It’s particularly helpful in caring for a patient with symptoms because it offers real-time/near real-time information about active infection. It may also detect disease one to two days before symptoms start.
PCR testing, however, does have limitations. Results depend on when the test is performed and the collection technique. Testing someone without symptoms could result in a negative result, but symptoms could develop the next day and a test would yield a positive. Whether an oral or nasal swab is used for collection and whether adequate material is collected also affect the test result. For those reasons, PCR testing can result in false negatives. It’s really important to have well-trained clinicians and public health professionals guide you through this nuance.
Who gets PCR tested varies depending on testing criteria guidelines issued by federal and state health agencies, on the availability of supplies like PPE, swabs and reagent, and on the need to allocate resources where the need is greatest. For instance, if a hot spot occurs like in Blaine County, resources may be shifted accordingly.
When it comes to PCR test results, St. Luke’s implemented a prioritization framework to determine which testing platform should be used and when. The key difference is turnaround time. Rapid tests are currently used for first responders, high-risk patients and people being admitted to the hospital. Other suspected cases can typically get a result in a day or two. The criteria may expand as reagent becomes more available and we gradually add back services, such as postponed surgeries and additional clinic visits.
We do need more PCR testing, but the testing needs to be applied wisely and expanded to target populations like health care workers, first responders and vulnerable communities such as nursing homes and congregated living facilities. We also need the ability to take random samples around our community at different intervals to find outbreaks before they get out of control.
But, testing in and of itself isn't a strategy alone. As capacity for testing expands and the criteria are loosened to allow for more widespread testing, it will be important to obtain results quickly, isolate those who test positive and implement contact tracing to identify people in contact with the infected person so they can take appropriate measures, too. This rapid response will help to prevent another widespread outbreak and our state’s reverting to the shelter-in-place order. Testing and contract tracing must go hand in hand.
The scientific community rapidly came together to collaborate and innovate to develop antibody testing. There has been a wealth of interest and hope in these tests as a way to move past this pandemic. We hope they help. The problem is, right now based on best available evidence, we don’t know if a positive test means that you are protected.
Antibody testing seeks to find if there are proteins that formed in response to infection and is a way to suggest a current or past infection. These tests are developing rapidly under emergency waivers from the FDA to encourage innovation and to speed delivery to the market. As of today, only four tests have gone through more rigorous authorization to be approved by the FDA and people should be vigilant in determining the authenticity of tests offered.
For many infections, antibody levels above a certain threshold indicate someone’s immune system has successfully fought off the virus and is likely protected from reinfection. But the accuracy of antibody tests remains under question and applies to the new COVID-19 tests, as well. Researchers still don’t know how much of an antibody response is needed to form immunity and how long it will last.
A test’s reliability is based on its sensitivity and specificity. Sensitivity refers to the ability to detect a disease when it is present. Specificity is the likelihood of a negative result when the disease is absent. Right now, most tests do not have high enough sensitivity and specificity to be considered reliable as a clinical indicator.
As of today, there’s not enough prevalence of the disease among the population of Idaho or the broader United States, so widespread antibody testing would result in too many false positives. To better learn about immunity, it’s better to test a smaller group that’s had a higher prevalence. That’s why antibody testing studies are underway in Blaine County, which had a higher percentage of people testing positive for the virus.
Of course, we cannot forget our foundational principles in fighting this disease. We need to continue to physical distance, wear masks in public and be diligent in performing infection-prevention hygiene measures to mitigate the spread of the virus. Doing our part will likely prevent a rapid COVID-19 resurgence that would overwhelm the health care system with very ill patients and lead to more deaths. COVID-19 will likely be here for the next 12-18 months. Continuing to follow these safety measures buys us time to study the virus and develop treatments and a vaccine. The tough news is this virus is not going anywhere and we need to outsmart it with good decisions and smart science. We can rise to the challenge and navigate living with COVID together.
Dr. Terry O’Connor is an emergency physician at St. Luke’s Wood River and medical director for the Blaine County Ambulance District.