“It correctly identified when cancer was present in 51.5% of cases, across all stages of the disease, and wrongly detected cancer in only 0.5% of cases.”
The headline says accurate. The number says it misses roughly half the cancers it looks for. A 0.5 percent false positive rate is good, and spread across millions of screened people it still means a lot of terrified patients. Grail, the company selling the test, gets the NHS pilot either way.