Reporting the study results on its blood test for colon cancer, late Thursday,
called the study a success. Some investors disagreed—knocking Guardant stock (ticker: GH) down 39% to $25 in aftermarket trading, while lifting shares of rival
(EXAS) 25%, to $56.
A pioneer of tests that look for DNA clues of cancer in a simple blood draw, Guardant spent three years testing 22,000 people for colorectal cancer in its Eclipse study. After Thursday’s market close, the Palo Alto, CA-based company said that its blood test demonstrated 83% sensitivity—meaning that it detected 83% of the group’s colon cancers. It showed 90% specificity—meaning that 10% of its positive findings were false positives.