Quest Diagnostics says hackers accessed patient records in ordering system breach

Quest Diagnostics said an unauthorized party appears to have accessed certain patient records after a breach of a system clients use to order lab tests and look up results.

The company learned on Oct. 21 of unauthorized access to its Quanum LSM system, according to an 8-K filed Thursday. Quest said it started its cybersecurity incident response, notified federal law enforcement and hired outside cybersecurity experts to help investigate.

"While the full scope of unauthorized access remains under investigation, at this time the Company believes that an unauthorized party accessed certain patient records," the filing said.

Operations not disrupted

Quest said the incident has not materially disrupted its business operations or its ability to serve patients. It is working to contain the activity, assess the nature and scope of the incident and put remedial measures in place.

The filing listed the incident, along with possible government investigations, lawsuits or private actions, among risks that could affect future results. It did not quantify the number of records involved or any expected cost.

The disclosure came the same morning Quest reported third-quarter results and raised its 2026 revenue and earnings guidance in a separate 8-K.

By the numbers

• System affected: Quanum LSM test ordering and results platform
• Discovery date: Oct. 21, 2026
• Data involved: certain patient records, per the company's current belief
• Operational impact: not material, according to the company

Sources

1. Quest Diagnostics Incorporated, Form 8-K (Item 8.01) filed Oct. 22, 2026, accession 0000947871-26-000941
2. Quest Diagnostics Incorporated, Form 8-K (Item 2.02) with Exhibit 99.1 earnings release dated Oct. 22, 2026, accession 0001022079-26-000097

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