The company has issued tens of thousands of corrected reports to patients and doctors after reportedly taking its Edison blood testing machines out of service last June.
The Wall Street Journal reports the move raises the possibility that many health care decisions may have been made based on inaccurate data.
Theranos’ Edison machine was seen as a key innovation leading to the company’s $9 billion valuation.
The machine was designed to perform a range of diagnostic tests from a single drop of blood.
But problems led the company to stop using the machines last June.