Hundreds of people in Massachusetts have been impacted by a Nov. 26 third-party data breach of an online patient portal of Quest Diagnostics Inc., a nationwide provider of diagnostic test services.

721 individuals with contact information in Massachusetts were affected by the breach, said Quest Diagnostics spokeswoman Kim Gorode in an email. She was unable to provide data regarding the number of Berkshire County residents affected by the breach.

The intrusion affected approximately 34,000 of about 4 million total users of Quest Diagnostics' online and application-based patient portal, MyQuest by Care360. All patients nationwide can utilize the portal to schedule appointments, access lab results and pay bills, Gorode said.

The company has one location in Berkshire County at 42 Summer St. in Pittsfield. Other sites in Western Massachusetts are located in Springfield and Florence.

Berkshire Health Systems does not utilize Quest Diagnostics.

"We are not affiliated with [Quest Diagnostics] in any way, shape, form or manner," said Michael Leary, spokesman for Berkshire Health Systems.

Gorode confirmed the accessed data included patients' names, dates of birth, lab results and in some cases, telephone numbers. Patients' Social Security numbers, credit card information, and insurance and financial information were not compromised. Affected patients were notified via mail, according to a company press release. There is currently no indication that patients' information was misused, according to the release.

Accessed lab results range from January 2010 to November 2016, Gorode said. No other breaches have occurred since Nov. 26, and the company has retained a cybersecurity firm to help investigate the incident and prevent future intrusions, Gorode said.

Quest Diagnostics, headquartered in Madison, N.J., annually serves one in three adult Americans and half the physicians and hospitals in the United States, according to the release.

The company has established a dedicated toll-free number to call with questions regarding the incident between 9 a.m. and 7 p.m. EST: 888-320-9970.

Reach staff writer Patricia LeBoeuf at 413-496-6247 or @BE_pleboeuf.