Explainer: COVID-19 Testing, Testing, One, Two, Three…

Making sense of the variety of tests being put into service to help stem the coronavirus pandemic and save lives
Credit: Visuals 3D via Pixabay
COVID-19

Like leaders in other states hard-hit by the novel coronavirus, Gov. Phil Murphy has repeatedly stressed that New Jersey’s public health and economic revival must be rooted in widespread, rapid-result testing of residents.

The governor called for doubling the Garden State’s testing capacity — approximately 10,000 tests a day — but has yet to detail what testing methods will be used and how these programs will be deployed across the Garden State. Since the outbreak began in early March, more than 116,000 residents have been diagnosed with COVID-19, including nearly 6,800 who died.

“Having a robust and greatly expanded testing program in place is vital to our being able to begin to reopen responsibly our state,” Murphy said last week during a daily press briefing that highlighted one of two COVID-19 tests developed by Rutgers University, one of which officials said could be scaled up in weeks to test 20,000 or even 30,000 people daily.

“Without testing, we will not be able to take the necessary steps to contain future cases and prevent them from becoming boomerang outbreaks,” he added.

Officials at the state Department of Health note that diagnostic tests — which can tell if the virus is currently present in someone’s body — are most useful for guiding public health actions, like deciding to quarantine infected individuals to prevent the spread of COVID-19.  These tests can be performed in various ways, involving swabs or saliva, and are now in use at more than 100 public and private screening sites in New Jersey, officials said.

There is also growing interest in antibody tests, generally performed by analyzing blood or plasma to find out if someone’s body contains an immunoglobulin — a protein developed by the immune system that indicates a person has at some point been infected. (Scientists are still studying how these antibodies may protect people against reinfection.) While the accuracy of some versions has been questioned, antibody screenings are now publicly available at some hospitals and labs in New Jersey and Trenton-based Capital Health is testing members of its workforce to give them peace of mind and to better understand the spread of the virus.

“We realized the highest-risk group getting infected and dying was health care workers” based on what we saw in Italy and New York, said Dr. Robert Remstein, director of accountable care at Capital. “We said, ‘we need to do something to protect our workforce beyond getting them personal protective equipment.’”

Patrick De Deyne, Capital’s head of clinical research, said the program was developed weeks ago when testing options were extremely limited and it will eventually involve close to 2,000 staff members, from those on the COVID-19 wards to housekeeping professionals. “Everyone is equally important,” he said.

Some states have started to deploy public antibody testing, including California and New York, which conducted random screening on 3,000 people at grocery stores and big-box outlets. One in five residents of New York City were likely infected, the state found; rates were lower in other areas. New Jersey is considering similar efforts, officials suggest.

The two types of test provide very different information, but experts believe both will be important as New Jersey and other states move forward. “You’ve got two options here: the snapshot of a moment in time versus watching a movie,” Murphy explained Wednesday, adding that state officials were working “morning, noon and night” on a testing strategy. “I suspect we will firmly come down on ‘we need both.’ And we need both for different reasons,” he said.

Diagnostic tests

In a diagnostic test, samples are taken from a patient’s respiratory system and analyzed for the presence of SARS-Cov-2, the virus that causes COVID-19. Initially, this required a nasopharyngeal or oropharyngeal swab, in which a clinician took a sample from deep within a patient’s nasal cavity or the back of their throat.

Specimens are sent to a lab, assembled into a batch and run through a machine, a process that can take as little as 24 hours to 48 hours but stretched to beyond a week as the system became overloaded. The results are either positive — someone has the virus — or negative; the test cannot determine if someone has been infected in the past, but it can detect the virus in someone who is not showing symptoms, experts note.

These were the techniques used at some of the first public testing sites in New Jersey, operated by the Federal Emergency Management Agency in conjunction with state and local officials, and initially limited to individuals who had fever, coughing or other COVID-19 symptoms. To date, roughly 2.7% of state residents have been tested.

But the collection process is invasive and uncomfortable for patients and requires significant staff and personal protective equipment, or PPE, the masks, gowns and other gear health care workers wear to avoid becoming infected. And the delay in processing created problems for public health officials seeking to contain the spread.

Researchers at Rutgers University tackled several of these problems. In March, David Alland, director of the Public Health Institute at New Jersey Medical School, announced that his team had worked with a molecular diagnostics company to create a “point-of-contact” test that could be processed on site in 45 minutes; the development was hailed as a game-changer in the coronavirus response. (Other even faster tests have since been developed elsewhere.)

In mid-April, Rutgers Professor Andrew Brooks, head of RUCDR — a Rutgers genetics research group based in Piscataway — announced his team had worked with a private lab to create a saliva-based diagnostic test, the first of its kind to receive federal approval. This version has the advantage of being noninvasive, thus requiring far fewer clinicians to collect samples and therefore less PPE; officials have chosen it for use in the state’s five centers for developmentally disabled adults and at 16 nursing homes in South Jersey. Processing the saliva does take 24 hours to 48 hours in a lab, however.

Antibody test

Another metric is the antibody — or serologic — test, which indicates exposure to the virus at some point in the past; different types of tests identify different forms of antibodies, which can change during the course of an immune response. But it could be another six months before experts can determine what level of protection these antibodies actually provide against reinfection, experts said.

“At this time there’s not enough information from these antibody tests to make a determination like a back-to-work determination,” said Dr. Christina Tan, New Jersey’s state epidemiologist.

While these tests aren’t useful in diagnosing a patient or making quarantine decisions, they can help researchers better understand the full impact of COVID-19, which can be spread by people who are asymptomatic. It can also be used to clear individuals who want to donate “convalescent plasma” in which white blood cells from those who had COVID-19 are given to new patients to help build their immunity.

But there are questions about the accuracy of these tests, and federal officials have approved just a handful of the more than 100 versions developed. People also react very differently to infections, with some producing more antibodies than others, further complicating the testing process.