Quest Diagnostics confirms cyberattack compromised patient records

Quest Diagnostics, a major U.S. medical laboratory operator, has disclosed a cyberattack that resulted in unauthorized access to patient records. The breach targeted the Quanum Lab Services Manager (LSM) system, a platform used by approximately 500,000 clinicians across North America to order laboratory tests, view results, and manage billing.

The company discovered the intrusion on October 21, 2026, and subsequently paused access to the affected system as a precautionary measure. While Quest confirmed that personal information and protected health information (PHI) were likely accessed, the exact number of affected patients and the specific nature of the compromised data have not yet been determined.

Quest Diagnostics has notified federal law enforcement and engaged external cybersecurity experts to investigate the scope of the incident. Although access to the Quanum LSM platform was temporarily suspended, the company stated that its core business operations remain functional. Healthcare providers can continue to place orders through alternative methods, such as paper requisitions, fax, or direct electronic medical record (EMR) interfaces.