New research from the manufacturer, Adaptive Biotechnologies, which is based in Seattle, found that the test was eight times better at detecting past COVID-19 infection than a commercially available antibody test.
Immunologists say the pre-print study still needs to be peer reviewed, but the results look promising and could replace antibody tests as a way to discover how widespread the virus is in a community.
When someone is exposed to a virus, different parts of the immune system are called to fight it off including antibodies and other immune cells.
Most of the attention has been focused on antibodies because testing for them is fast and inexpensive. But they usually diminish over time.
'The source of the antibodies - the factory that makes them - dies off within a few months,' Dr Akiko Iwasaki, an immunologist at the Yale School of Medicine, told CNN.
Recent research, on the other hand, has found T-cells may be sufficient enough to offer protection against the virus.
'For other viruses they've been shown to persist for years. For this virus we don't know how long they last, but we would expect for a couple of years at least,' Iwasaki said.
A study published on Tuesday from the UK, conducted by Oxford Immunotec and Public Health England, found that no participants with a high T-cell response developed symptoms when infected with COVID-19.
By comparison, 20 people with low T-cell responses, who experienced fever, cough or shortness of breath.
However, isolating T-cells is very time consuming because there are trillions of them that each recognize a different molecule and scientists have to identify the 20 or 30 that recognize the coronavirus.
After separating immune cells from blood samples, the cells are washed and counted.
For the research, which has not been published yet and was not funded by Adaptive, the team looked at samples from 2,200 people in Vo, Italy - which became the epicenter of the pandemic in its region of Veneto.
Of the 70 people who had had confirmed cases of coronavirus, the test, called T-Detect, correctly identified 97 percent of cases, only missing two of them.
By comparison, a commercial antibody test called DiaSorin only correctly identified 77 percent of cases, missing 16 of them.
This means the test is eight times more effective at determining whether or not someone was previously infected with COVID-19.
What's more, of more than 2,000 people who tested negative for the virus, the T cell test returned positive results for 45 people.
Dr Lance Baldo, the chief medical office at Adaptive and coauthor on the paper, told CNN that believes most of the 45 people never realized they were infected.
About half of them either had mild symptoms or had lived with someone tested positive for COVID-19, or both.
Adaptive said it is planning this month to file an application for Emergency Use Authorization (EUA) from the US Food and Drug Administration.
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