COVID tests not all created equal, experts say 



BAR HARBOR — “Most people in this country are not used to seeing science happening in real time,” said Dr. J.R. Krevans Jr., of Mount Desert Island Hospital, in a virtual town hall last week. “And those of us who are used to that are not used to seeing science happening at 60 miles an hour, which is what’s happening.” 

He and Dr. Jonathan Epstein of the University of Pennsylvania medical school, with which MDI Hospital has a longstanding partnership, gave an update on research into the SARS-CoV-2 coronavirus that causes the COVID-19 disease. They also discussed the development of new types of tests for the virus. 

“People when they get a yes/no answer from a test think it’s an absolute,” Krevans said. None of these tests are an absolute.” 

The PCR molecular tests, which the Maine Center for Disease Control is recognizing as the “gold standard,” are the most accurate. These tests recognize the actual genetic material of the virus. They require expensive reagents that have been hard to come by and analyzing the samples is a “cooking process done on a complicated instrument,” Krevans said. 

Antibody tests, which look for signs that the body has produced a reaction to the virus, are a way to ask, “does your body recognize COVID-19,” he said. These tests are more helpful for “global study” of how the virus is moving through a population, the physicians said, than they are for making individual health care decisions. 

The frequently marketed “finger stick antibody test … is of no real value,” Krevans said. “Early in infection, when you are most infectious, your antibody test will be negative.” 

Epstein agreed. “People were getting misleading information,” he said. “Antibody tests are not useful for determining if you have the disease or not.” 

A third group is antigen tests, which recognize the proteins on the surface of the virus that interact with human cells. These can be analyzed much faster and at less cost, Krevans said, because “you can recognize proteins with simple, either visually or machine-read, tests.” 

Some of the recently approved saliva-based tests are in this category. Both speakers were enthusiastic about their potential to make testing much more affordable. 

If we can drive that cost down below a dollar a test, that’s going to be critical to make surveillance testing feasible,” Epstein said. And surveillance testing (regular asymptomatic testing of a portion of a population) is going to be important until we can get a vaccine up and going.” 

“Even if the (antigen) tests lack a little sensitivity, if you can use them more often, you’ll catch (the cases),” he continuedThe amount of virus (in the body) skyrockets during the peak phase of infectivity. If you’re able to test frequently, you’ll catch it when it’s peaking, and that’s when it’s most important to catch it.” 

There are at least three surveillance testing programs underway or in the planning states on Mount Desert Island. 

A program for public-facing workers in tourism businesses began in July and is set to run through October. Each of a group of 200 workers is being tested once every two weeks. At press time, that program had not had any positive test results. 

At College of the Atlantic, all faculty, staff and students who will be on campus for the fall term are set to undergo a series of PCR tests before classes begin Sept. 11. After that, a surveillance program includes testing 20 percent of the college community each week. 

The college is partnering with the Broad Institute of MIT and Harvard to have the samples analyzed there. COA will report test results to the Maine CDC and students will likely be listed as Hancock County residents for reporting purposes. Anyone at the college who becomes symptomatic will be directed to MDI Hospital for a test, according to college spokesperson Rob Levin.  

A third program is in the works for employees of the MDI Regional School System. The details of that program have not been finalized, hospital spokesperson Oka Hutchins said, but “we are working with the school to support their sentinel testing program and are currently exploring several laboratory and funding options to best meet their needs.” 

 

 

Liz Graves

Liz Graves

Reporter at Mount Desert Islander
Former Islander reporter and editor Liz Graves grew up in California and came to Maine as a schooner sailor.

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