A new blood test has shown ability to screen numerous types of cancer with a high degree of accuracy. A trial of the test showed it detected and localised more than 20 types of cancers. The test developed by biotechnology company Grail Inc uses next-generation sequencing technology to probe DNA for tiny chemical tags (methylation) that influence whether genes are active or inactive. When applied to nearly 3600 blood samples -- some from patients with cancer and some from people who had not been diagnosed with cancer at the time of the blood draw -- the test successfully picked up