The Food and Drug Administration has issued an emergency use authorization for a new coronavirus testing method using the body’s T-cells — which could help better diagnose COVID long-haulers.

The T-Detect COVID-19 test — developed by Seattle-based Adaptive Biotechnologies Corp. in collaboration with Microsoft — is billed as a “next generation” screening method that analyzes DNA from T-cells in blood samples instead of current testing methods that screen for immune proteins.

“The T-Detect COVID test will be a useful tool to help determine if a person previously had COVID-19,” the FDA announced Friday. “This is especially important for people who may have exhibited symptoms previously or believe they have been exposed but have not tested positive.”

Medical staff members work in the Intensive Care Unit (ICU) where patients suffering from COVID-19 are treated at the Melun-Senart hospital, near Paris, France on March 8, 2021.Benoit Tessier/Reuters

The company’s chief medical officer told Bloomberg prior to the FDA’s approval that the $150 test may help people who think they’ve been infected but haven’t been diagnosed — especially so-called “long haulers” who have had symptoms persist for weeks or months.

“Some of these people were never diagnosed,” Adaptive’s Lance Baldo told Bloomberg in January. “Sometimes their physicians are wondering, and — frankly, this is where it gets ugly — sometimes their insurers are wondering.”

Medical workers wearing protective masks and suits walk in an intensive care unit at the Oglio Po hospital, where patients suffering from COVID-19 are treated, in Cremona, Italy on March 19, 2020. Flavio Lo Scalzo/Reuters

The blood test extracts DNA from T-cells and then uses machine-learning software developed in a partnership with Microsoft to determine if the person has been previously infected with the virus.

“We’re looking for that imprint, like a crime scene investigation,” Dr. William Li, a T-Detect prescribing physician, explained to ABC News Tuesday.

“So many people had the disease, recovered, never got a clear-cut diagnosis, yet they’re suffering from these bizarre, persisting symptoms. The T-cell test has been really useful in this long tail of COVID to help patients establish where they are.”

A technician conducts COVID-19 tests at a new facility on Oct. 30, 2020, in Valencia, Calif.Marcio Jose Sanchez/AP Photo

Baldo told ABC News that T-cells work as the immune system’s front-line “foot soldiers.”

How long their response stays in the body remains unclear, but UK research suggests up to six months — potentially longer than antibodies, Bloomberg reported.