Dozens of patients in central Newfoundland are being retested because of separate problems with some hospital equipment and paperwork.
Central Health says 98 patients will have to undergo pulmonary function tests, after the regional health authority found that equipment used to calibrate machines had malfunctioned.
The tests in question had been done between mid-January and mid-February.
Dr. Raj Brahmbhatt, chief of medical staff at James Paton Regional Health Centre in Gander, said the likelihood of patient harm is "anticipated to be minimal" because other tests are done, but the authority is not taking chances.
"The impact on patients cannot be known with certainty until retesting has been completed," he said in a statement.
All applicable patients are expected to be notified by Tuesday.
Meanwhile, Central Health disclosed that there have also been problems with tests done for sleep apnea patients.
In that case, paper copies of some studies were not bring printed and sent to the physician who ordered the test.
"Some sleep studies were not reviewed by the appropriate physician and this may have an impact on patient care," Central Health said in a statement.
Some 758 tests done for 719 patients have been reviewed. So far, the review has found that 93 per cent of patients "received appropriate follow-up."
The authority said 34 tests had not been reviewed by the right doctor, while the status of another 18 tests is not yet determined.
"Ordering physicians are currently in the process of determining if unreviewed reports have had any impact on patients," the authority said in a statement.
"At this point in time Central Health is unable to determine if there has been patient harm as a result of this issue. An update will be provided once this investigation is complete."