Quest Diagnostics has disclosed a cyberattack involving unauthorized access to its Quanum LSM system, which healthcare clients use to order laboratory tests and view results. The company discovered the incident on October 21, 2026, and suspended access to the platform while investigating whether patient records were exposed.

The affected service, Quanum Lab Services Manager, supports test ordering, delivery of results, and searches for previous results. In its official incident notice, Quest said its core business operations remained running. The company said the incident had not materially disrupted its ability to serve patients.

Patient Information Accessed

Quest’s public update confirmed that patient health information or personally identifiable information was involved in the unauthorized access. However, investigators were still determining exactly which information was affected. The company had not disclosed how many patients were involved or provided a detailed breakdown of the records accessed.

That distinction matters. Access to a system containing medical records does not establish that every record was stolen. Quest’s statements describe unauthorized access and potentially affected patient records, but do not establish the full scale of any data theft. Claims about specific stolen information therefore remain unconfirmed.

According to its SEC disclosure, Quest started its incident response procedures, brought in outside cybersecurity experts, and notified federal law enforcement. The response includes containing the activity, investigating its scope, and taking corrective steps. Public reporting has not identified the attackers or their entry method.

Providers using direct customer laboratory information system interfaces or electronic medical records can continue placing orders through those connections, which Quest said were unaffected. Suspending Quanum LSM access therefore does not mean all electronic ordering stopped. Quest said it was working to restore access as soon as possible.

The incident follows other breaches involving medical testing services, including the Laboratory Services Cooperative data breach and the LifeLabs cyberattack. Those separate cases offer context, not evidence of a shared attacker.

Quest said it would make legally required notifications as investigators determine which patient information was affected by this latest incident.

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