Dr. Beverley Carter told the Cameron inquiry that poor processing caused errors with breast cancer tests. (CBC)

A St. John's pathologist has told a judicial inquiry she's certain about what caused flawed lab tests involving hundreds of breast cancer patients: errors were made in the procedures used for hormone receptor tests.

Dr. Beverley Carter told the Cameron inquiry Tuesday that several other possible factors can be eliminated because of subsequent retesting.

For instance, Dr. Brendan Mullen, an expert at Mount Sinai Hospital in Toronto — which began retesting hundreds of estrogen receptor and progesterone receptor (ER/PR) tests in 2005 after flaws were identified — has already testified that pathologists had made the correct interpretations, based on what they were given.

At the earliest stages of testing, when tissues samples undergo a process called fixation, Carter said that subsequent retests showed preparatory steps were not at issue.

Only 1 conclusion left, Cameron told

Carter told Justice Margaret Cameron that left her with only one conclusion.

'[Lab managers] had demonstrated that they didn't have a lot of in-depth knowledge of the issues that were at hand, and I thought that this investigation could go down some wrong paths.'—Beverley Carter

"You would have to think that it's the testing procedure itself," Carter said.

In documents already presented to the inquiry, Carter has been critical of how Eastern Health managers oversaw the lab.

In direct testimony, Carter backed up that view, and said the lab was not given the attention it needed. Lab technologists and others have already testified that they were not given much, if any, specialized training in the complicated process of handling ER/PR tests.

"I think my largest concern was with the management structure that we had in the lab," Carter told Cameron.

"This was, I mean, a fairly serious issue and a lot of the decisions that were being made were being made by the management team in the lab."

Lab management comes under fire

Carter suggested that lab management did not appreciate the complexity of what technologists had to handle.

"I felt [they] had demonstrated that they didn't have a lot of in-depth knowledge of the issues that were at hand, and I thought that this investigation could go down some wrong paths," she said.

Barry Dyer, the manager of Eastern Health's pathology lab, testified earlier this month about what he called unfair criticism from physicians, and about battles over "territory" in the lab's work.

Lack of documentation troubling, judge told

Meanwhile, Carter said she was disturbed by how little documentation was generated during the testing process by the Eastern Health pathology lab.

"I wasn't happy that there was no documentation," she testified.

"It's a basic sort of tenet of laboratory life — actually increasingly becoming more of all health care — that you document everything, but especially when you're doing laboratory testing … even if you get your blood taken," she said.

Carter said the lack of documentation impaired quality control work in the lab.