Quest Diagnostics Discloses Breach of Quanum LSM System; Patient Records Accessed
DGX sits 38% above its 52-week low of $171.175.
Summary
Quest Diagnostics reported unauthorized access to its Quanum LSM ordering and results system on October 21, 2026, and believes certain patient records were accessed. Operations were not materially disrupted, per the company, and the full scope remains under investigation.
Key Events · Legal and Risk Events · DGX
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Quanum LSM System Breached
On October 21, 2026, Quest learned of unauthorized access to its Quanum LSM system, which clients use to place test orders and receive and look up results.
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Patient Records Likely Accessed
The company believes an unauthorized party accessed certain patient records; the full scope of the access remains under investigation.
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Response Underway
Quest activated its cybersecurity incident response procedures, notified federal law enforcement, and engaged external cybersecurity experts.
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Operations Not Materially Disrupted
The filing states the incident has not materially disrupted business operations or the company's ability to serve patients.
Analysis · DGX · Industrial Applications And Services
Quest disclosed that an unauthorized party accessed its Quanum LSM system, which clients use to place test orders and retrieve results, and that certain patient records were likely accessed. Operations were not materially disrupted, according to the company, but the scope remains under investigation, so the real exposure is unknown: notification obligations, potential HIPAA or state regulatory action, and customer remediation costs all hinge on how many records were involved. Landing the same day as a strong Q3 beat and guidance raise, this is the one item that could offset an otherwise positive news day.
How filings like this one have moved
In the 30 days to Oct 22, 2026, 29.4% of the 1560 measured filings Wiseek scored 7 moved their stock by 5% or more by the next session's close. The median move was -0.47%. These are measured outcomes after filings of this importance, not a forecast for this one.
Measured one observation per ticker per day, after exclusions. Current figures: Filing Impact Tracker · open dataset
At the time of this filing, DGX was trading at $236.57 on NYSE in the Industrial Applications And Services sector, with a market capitalization of approximately $26.4B. The 52-week trading range was $171.18 to $248.84. This filing was assessed with negative market sentiment and an importance score of 7 out of 10.