South Nassau Communities Hospital is sending out 4,247 letters to patients recommending they be tested for hepatitis B and C and HIV because of the risk of infection from an insulin pen.

In the letter dated Feb. 22, the Oceanside hospital said the patients may have received insulin from an insulin pen reservoir -- not the pen's single-use disposable needle -- that could have been used with more than one patient.

An insulin pen for those with diabetes is a pre-filled syringe meant to be used to dispense insulin in a single patient. Because of potential backflow of a patient's blood into the pen cartridge after injection, using a pen on multiple patients may expose them to blood-borne infections.

Hospital spokesman Damian Becker said no one was observed reusing the insulin pen reservoir on more than one patient, but a nurse was heard saying it was all right to do so.

"Once that was said, we then followed through with a report to the state Department of Health," Becker said.

The hospital said risk of infection is "extremely low."

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"Nonetheless, out of an abundance of caution, the hospital is recommending that patients receiving the notification be tested for hepatitis B, hepatitis C and HIV. While the testing is voluntary, it is recommended," the hospital said.

Becker said Tuesday the hospital, which is sending the letters out in phases, has received about 200 phone calls so far. The last letters should be received by March 17, Becker said.

It will take patients about two weeks to receive test results, he said.

The hospital said it has since banned the use of insulin pens and permits only the use of single-patient-use vials.

The state Department of Health said that last year three health facilities reported potential insulin pen re-use: two state-regulated facilities and the Veterans Administration's medical center in Buffalo.

South Nassau is offering free and confidential blood testing and has set up a dedicated telephone line for those patients notified. To arrange a test, call 516-208-0029.

Insulin pen misuse is not uncommon.

In May 2008, Nassau University Medical Center in East Meadow notified 840 patients that nurses may have been using insulin pens on multiple patients.

In 2009, following reports of improper use of insulin pens in hospitals, the U.S. Food and Drug Administration issued an alert reminding health care workers that insulin pens are meant for use on a single patient only.

In 2012, the U.S. Centers for Disease Control and Prevention said that "in spite of this alert, there have been continuing reports of patients placed at risk through inappropriate reuse and sharing of insulin pens," and it put out a clinical reminder on their proper use.

Last year, the VA issued an alert systemwide following the report of insulin pen misuse at its Buffalo hospital. Of 395 patients tested, 12 were found with hepatitis B and six with hepatitis C.