Quest Diagnostics has confirmed that unauthorized users accessed its Quanum LSM platform, potentially compromising patient records. The U.S. clinical testing company discovered the incident on October 21, 2026, and said it has begun an investigation with assistance from outside experts and law enforcement agencies.
Quest Diagnostics investigates unauthorized access
Quest Diagnostics said it activated its incident response procedures to “contain the activity, assess and investigate the nature and scope of the incident, and implement appropriate corrective actions.”
“On October 21, 2026, Quest Diagnostics Incorporated learned of unauthorized access to the Quanum LSM system used by certain customers to place test orders, receive results, and examine results,” the company said in a filing with the U.S. Securities and Exchange Commission (SEC).
The company is still investigating the incident but believes that some patient records were compromised. It has not yet determined what types of data may have been affected.
Quest Diagnostics disclosed the incident to the SEC and has provided additional information in a notice on its website.
Quanum LSM access suspended
Quanum LSM is Quest Diagnostics’ online lab services platform. Physicians, hospital staff, and medical office staff use it to manage testing services, access results, track test status, and order supplies. The company provides more information about the platform in its lab service manager documentation.
Quest Diagnostics said customer-facing operations were not disrupted and that no direct customer-facing laboratory information system (LIS) interface or electronic medical record (EMR) users were affected.
As a precaution, the company has temporarily suspended access to other systems, including Essential Insights and LabHQ. The Quanum LSM system is currently unavailable, and Quest recommends using paper invoices or Quanum eLabs to order tests and receive results.
Outside experts are assisting with the investigation, while Quest Diagnostics is providing information to the appropriate law enforcement agencies.
At the time of reporting, no threat group had publicly claimed responsibility for an attack against Quest Diagnostics.
Quest Diagnostics’ healthcare operations
Quest Diagnostics is a major U.S. clinical testing company that provides diagnostic tests and services for a broad range of medical conditions. It operates 7,700 locations across North America, employs 65,000 people, and generates more than $11 billion in annual revenue. According to company information, one in three U.S. adults receives services from Quest Diagnostics each year.
The incident follows a major breach disclosed in 2019 at claims collection provider American Medical Collection Agency (AMCA), which compromised the data of approximately 11.9 million Quest Diagnostics patients.
At least 19 class-action lawsuits were filed against Quest Diagnostics after that disclosure. The lawsuits were consolidated into a multidistrict lawsuit, which remains ongoing and unresolved.
Source: www.bleepingcomputer.com