Quest Diagnostics confirms data breach exposed patient records

American clinical laboratory company Quest Diagnostics disclosed that patient records have been exposed after a threat actor gained unauthorized access to its Quanum LSM system.

The company learned about the breach on October 21 and deployed its incident response protocol "to contain the activity, assess and investigate the nature and scope of the incident and implement appropriate remedial measures."

“On October 21, 2026, Quest Diagnostics Incorporated learned of unauthorized access to its Quanum LSM system, which certain clients use to place test orders, receive and look up results,” the company says in a filing with the U.S. Securities and Exchange Commission (SEC).

Quest Diagnostics is a major clinical laboratory company in the United States, providing diagnostic testing and services for a wide range of medical conditions.