Hausfeld files nationwide class action against Quest Diagnostics over patient data breach

On October 30, 2026, Hausfeld LLP and co-counsel, Seeger Weiss LLP, filed a putative nationwide class action in the U.S. District Court for the District of New Jersey against Quest Diagnostics Incorporated, one of the largest clinical laboratories in the world. The suit is brought on behalf of patients whose personal and medical information was compromised in a breach of Quest's Quanum Lab Services Manager (Quanum LSM) system.

Quanum LSM is a web-based platform that physicians, hospitals and medical-office staff use to place lab test orders and to receive and look up patient results. According to Quest's October 22, 2026 filing with the U.S. Securities and Exchange Commission, the company learned of unauthorized access to the system on October 21 and believes an unauthorized party accessed certain patient records. Quest has since confirmed that protected health information and personally identifiable information were involved. It has not disclosed how long the intruder had access, how access was obtained, or how many patients were affected.

The complaint alleges that the records accessible through Quanum LSM include patients' names, dates of birth, contact and insurance information, the tests ordered, diagnosis codes and laboratory results. Unlike a credit card number, a lab result cannot be cancelled or changed once exposed. The complaint alleges this information equips criminals to commit medical identity theft and to craft convincing phishing and extortion schemes that reference a victim's real medical care.

The complaint further alleges that Quest, which serves roughly one in three American adults each year, failed to implement the authentication, access controls, monitoring and data-minimization practices required of an internet-facing portal to patient records. It points to Quest's prior security incidents in 2016, 2019 and 2021 as evidence that the company was on notice of the risks.

The named plaintiff, Robert Cooke of Nottingham, New Hampshire, received laboratory testing from Quest as recently as October 5, 2026. He seeks to represent a nationwide class of all individuals in the United States whose information was accessed, acquired or otherwise compromised in the breach, including everyone to whom Quest sends notice of it.

The lawsuit asserts claims for negligence, breach of implied contract, unjust enrichment, and declaratory and injunctive relief. It seeks damages and restitution, long-term credit, identity-theft and medical-identity monitoring at Quest's expense, and an order requiring Quest to adopt stronger security measures, including independent audits, phishing-resistant multi-factor authentication and real-time monitoring of record access.

The Hausfeld team includes Thomas E. Loeser, Steven M. Nathan, Mandy Boltax, and Ramon Rodriguez Jr. They are joined by Christopher A. Seeger and Shauna B. Itri of Seeger Weiss LLP.

The case is Cooke v. Quest Diagnostics Incorporated, No. 2:26-cv-14163 (D.N.J.).

If you believe you may have been affected, learn more on our Quest Diagnostics Data Breach page.