A Madison-based health clinic is investigating whether several thousand former patients were exposed to blood borne diseases after a former nurse used injection devices incorrectly for years.

Following an internal review, Dean Clinic found the nurse had improperly used insulin demonstration pens and finger stick devices, both used for diabetes treatment, on patients between 2006 and 2011, according to a statement from the clinic. The misuse could have exposed thousands of patients from various clinic locations to Hepatitis B, Hepatitis C and HIV.

A list of 2,345 former patients will receive phone calls and letters addressing their potential exposure to the diseases and to determine if testing is needed, the statement said. The clinic said one of its top priorities will be working with the patients to determine the proper next steps and to answer any questions.

Dean Clinic spokesperson Melissa Wollering said the insulin demonstration pens are used to instruct diabetic patients on how to administer insulin and are not meant to be used on patients, but instead intended to pierce something penetrable like a pillow or an orange.

Wollering said a fellow employee originally notified the clinic that the former employee was using the pens on the patients, which sparked the investigation. The former employee also misused finger stick devices, which are another diabetic instrument, she said.

Although the finger stick devices can be used on patients, the cartridge encompassing the device needs to be removed after each patient. While the former employee did remove the needle at the end of the device, Wollering said the former employee failed to remove the cartridge itself.

Through their investigation, Dean Clinic concluded the risk of exposure is isolated to just the 2,345 patients on the list, the statement said. Patient care staff will be reeducated on the correct use of these and similar devices to prevent similar incidents in the future.

Wollering said it is still uncertain whether any of the at-risk patients have been infected with a blood borne disease because of the mistake, but said the investigation into patient care has only just begun.

“We just started the process of contacting patients,” she said, “It will take some time for us to get the test results back.”

University of Wisconsin Health spokesperson Lisa Brunette said the chance of an exposure when blood drawing devices are applied to multiple patients is often close to zero percent.

Every clinic and health organization has some policy of continuous quality improvement to ensure that their techniques and equipment are up to date and safe, she said.

In an incident where an organization discovers a medical equipment or procedure being inappropriately used, Brunette said, a clinic generally takes it upon itself to re-educate the staff and provide any treatment to the patients who could have been involved.