Quest Diagnostics, one of the largest laboratory testing companies in the United States, has confirmed that an unauthorised party accessed patient records through one of its key ordering systems. The company learned of unauthorised access to its Quanum Lab Services Manager system on 21 October 2026 and disclosed the incident in a filing to America's Securities and Exchange Commission the following day.

What Quanum LSM does

Quanum LSM is the firm's online platform that physicians, hospital personnel and medical office staff use to manage laboratory services, access test results, track status and order supplies. That is why the breach reaches beyond Quest's own offices into clinics and practices that rely on it. Quest says it serves one in three adults in the United States each year.

Systems paused, paper forms brought back

As a precaution, Quest temporarily paused access to Quanum LSM and to two related systems, Essential Insights and LabHQ, while customers were told to use paper requisitions or Quanum eLabs instead. The company says the incident has not materially disrupted its business operations, and that users of direct laboratory-system interfaces or electronic medical record integrations were not affected. It has notified federal law enforcement and brought in outside cybersecurity experts to investigate.

Much remains unknown, and that matters

Quest has not said how many patients are affected, what specific data fields were taken, how the intruder got in, or who was responsible, and no threat group had publicly claimed the attack. Its own notice confirms that personal information and patient records were involved, but says the specific data is still being determined, and affected patients will be notified as required by law, with resources including credit and identity monitoring. Patients should treat unsolicited messages about lab results with extra caution and watch for an official notification letter.