Former Theranos lab worker details concerns about company's ability to conduct blood tests

Erika Cheung, a former Theranos lab worker turned whistleblower, testified Wednesday during the trial of founder Elizabeth Holmes about how she grew increasingly uncomfortable about the startup's ability to accurately conduct blood tests on patients.

In her testimony, Cheung detailed her growing concerns about the company's devices failing quality control tests in the research lab as well as what she said was a manipulation of data to pass quality control. This made her question the capabilities of the startup's proprietary testing machine, which she said was only being used on a small number of tests at the time it was hailed as the company's revolutionary innovation.

At times, she said, Theranos employees would delete up to two out of six data points as part of a test in order to pass quality control. She said there appeared no standard protocol within Theranos for when outlier deletion was appropriate, but noted it was something that happened "frequently" inside the company and said it would "normally be considered cherry-picking."

Cheung testified that she raised her concerns with higher-ups, including having a conversation with a top Theranos executive who she said dismissed her as being unqualified to weigh in. She said she was told she had little visibility into the company. Cheung quit soon thereafter, just six months after first joining the blood-testing startup in 2013 as a recent college graduate.

Cheung first took the stand Tuesday as the government's second witness in the long-awaited trial of Holmes, who faces a dozen counts of federal fraud and conspiracy charges over allegations she knowingly misled investors, patients, and doctors about the capabilities of her company's proprietary blood testing technology. Holmes, who has pleaded not guilty, faces up to 20 years in prison.