Quest Diagnostics confirmed Thursday that patient health information or other personally identifiable information was accessed in a cybersecurity breach that prompted the company to temporarily suspend access to several systems. The New Jersey-based testing company said it disabled access to its Quanum Lab Services Manager (LSM) platform after discovering unauthorized access on Wednesday and expects to restore full functionality as soon as Friday.
Quanum LSM allows certain healthcare providers to order laboratory tests and retrieve results. Quest said it believes some patient data was accessed but is still investigating what specific information was involved and how many people may have been affected.
Quest Diagnostics systems and response
As a precaution, Quest temporarily paused access to its Essential Insights and LabHQ systems, stating no data was accessed on those platforms. The company said its core operations remain unaffected and its ability to serve patients has not been materially disrupted.
Healthcare providers who normally use Quanum LSM can place orders via paper requisitions or through Quest’s Quanum eLabs platform; other electronic ordering systems remain operational. Quest said it has stopped the unauthorized access, is working to restore the affected system, and does not expect testing delays for clients who do not use Quanum LSM.
In a Thursday filing with the Securities and Exchange Commission, Quest said it notified federal law enforcement authorities and enlisted outside cybersecurity experts to assist with the investigation and response. The company said it is working to identify affected patients and healthcare providers and will issue notifications as required by applicable law.
Quest reported approximately $11 billion in revenue in 2025. The company noted this incident follows a 2019 breach involving a third-party billing provider, American Medical Collection Agency, which had reported unauthorized access to a system containing information associated with about 11.9 million Quest patients; Quest said its own IT systems were not involved in that incident.
Quest has not disclosed whether the latest breach will result in financial consequences and declined further comment.
