Shares of Guardant Health Inc. fell 27% Friday — their largest-ever single-day drop — after the biotechnology business reported that its blood test for colorectal cancer performed worse than expected in a recent study.
In a press release late Thursday, the Redwood City company said its test accurately found the presence of cancer 83% of the time. But the screening also delivered false positive results 10% of the time, and it was only to detect the presence of benign tumors that can turn cancerous…
