A game changing new blood test is able to screen for numerous types of cancer with a stunningly high degree of accuracy.

Developed by GRAIL, Inc., the test next-generation sequencing technology to probe DNA for tiny chemical tags (methylation) that influence whether genes are active or inactive. Scientists at the Dana-Farber Cancer Institute used the test on almost 3,600 blood samples, some from patients with cancer, some from people who had not been diagnosed with cancer at the time of the blood draw. In the end, they found that the test successfully picked up a cancer signal from the cancer patient samples, and correctly identified the tissue from where the cancer began (the tissue of origin).

The researchers found that the test’s specificity, which is its ability to return a positive result only when cancer is actually present, was particularly high, as was its ability to pinpoint the organ or tissue of origin.

The test searches for DNA, which cancer cells shed into the bloodstream when they die. Unlike “liquid biopsies,” which detect genetic mutations or other cancer-related alterations in DNA, the new test focuses on modifications to DNA known as methyl groups. These are chemical units that can be attached to DNA in a process called methylation, to control which genes are “on” and which are “off.” The abnormal patterns of methylation typically turn out to be more indicative of cancer, and cancer types, than mutations are.

In contrast, the new test zeroes in on portions of the genome where abnormal methylation patterns are found in cancer cells.

“Our previous work indicated that methylation-based assays outperform traditional DNA-sequencing approaches to detecting multiple forms of cancer in blood samples,” explained the study’s lead author, Geoffrey Oxnard of Dana-Farber. “The results of the new study demonstrate that such assays are a feasible way of screening people for cancer.”

The overall specificity of the new test was an astonishing 99.4%, which means only 0.6% of the results incorrectly indicated that cancer was present. Going forward, this might just change the way that cancer is both detected and treated.