Eastern Health president Vickie Kaminski revealed Tuesday that mistakes had been uncovered in the health authority's biochemistry lab in St. John's. (CBC)

A problem with some test results involving people taking an immunosuppressive drug has been uncovered at a lab operated by Eastern Health, Newfoundland and Labrador's largest health authority.

As a result, health officials are recommending that more than 200 patients be retested.

The health authority confirmed Tuesday that it has discovered a problem with its procedure to track blood levels of the drug Cyclosporine. The anti-rejection drug is used to suppress the immune system in patients who have undergone an organ transplant or have certain diseases.

However, too much of the drug can possibly cause kidney damage.

The authority said 235 patients who have been treated with Cyclosporine since last June are affected. Eastern Health said it is contacting the patients' doctors to arrange retesting, and it has also stopped the testing at its lab at the Health Sciences Centre in St. John's.

"I know the anxiety that can be raised within our patients when errors are made and I apologize for that," Vickie Kaminski, the president of Eastern Health, said in a news release. "We are taking quick action to ensure we can alleviate the concerns of our patients as quickly as possible."

Health officials confirmed that a preliminary review of 124 patients in the previous 24 hours indicated that four patients required a change in the dose of Cyclosporine and two of those four showed a slight deterioration of the kidney.

Tests done in Halifax

Eastern Health said concern was raised during the week of Feb. 8 when an acutely ill patient who was receiving Cyclosporine had a blood test that showed "a lower than expected presence of the drug, prompting examination of the testing procedure itself."

The tests were being performed at the biochemistry lab at the Health Sciences Centre in two machines, one of which only went into service for Cyclosporine testing in June 2009.

As a result, Eastern Health stopped the lab testing on Feb. 12, and since then the tests have been done in Halifax.

Health officials said the new equipment used for the testing in St. John's was calibrated incorrectly.

"We will continue our internal investigation of this incident over the coming days," Kaminski said in the release.

She said an outside agency has been hired to do an external review of the biochemistry lab. The health authority has also set up a toll-free information line for patients being treated with Cyclosporine who have questions.

This is not the first time Eastern Health has dealt with a problem in one of its labs.

A judicial inquiry was set up after it was revealed that mistakes were made on hundreds of tests that were conducted at the health authority's pathology lab between 1997 and 2005 to determine breast cancer treatment.

Last week, a Supreme Court judge in Newfoundland and Labrador approved a $17.5-million settlement in a class-action suit over the errors.