The former head of the authority at the centre of Newfoundland and Labrador's breast cancer inquiry says he backed but did not initiate a move to block the release of information about flawed lab tests.

George Tilley says he cannot recall who came up with the idea of not disclosing full information about flawed breast cancer tests. (CBC)

George Tilley, the former chief executive officer of Eastern Health, also said Thursday that he has thought "a million times" about decisions Eastern Health made to not publicly disclose what it knew about the tests, which may have prevented scores of patients from receiving the best possible treatment.

As well, Tilley testified that he could not recall who came up with the idea of not telling the media in late 2006 about all it knew about flawed hormone receptor testing, used to help guide the treatment that breast cancer patients receive.

During his fifth day of testimony at the judicial inquiry on the tests, Tilley was grilled over the authority's decision to sit on important information while it prepared for a December 2006 media briefing.

The inquiry was told that officials chose not to reveal information about the error rate of retested samples, even though it expected the media would ask questions about it.

Inquiry co-counsel Bern Coffey noted that a ministerial briefing note had "no hedging" about the data. At the briefing, officials would say the error rate — a phrase that they did not even like to use — could be as low as 10 per cent.

However, the authority had data, which would be disclosed a few months later in documents registered with a then-pending class action lawsuit in Newfoundland Supreme Court, that showed that more than 40 per cent of the tests were wrong.

"What are your feelings about or thoughts about whether it should have been apparent to you at the time, and the people around you?" Coffey asked Tilley.

"Well, you know, Mr. Coffey, I've thought about that issue a million times, and I've had a lot of time to think about it," Tilley said.

"I [had previously] acknowledged the fact that in retrospect that number, by not having it there, just added more complications to this issue than should have been the case. So, if I had known and had the benefit of hindsight then, there's a lot of things that one would do differently."

The issue erupted in a public furor in May 2007, with the Newfoundland and Labrador government calling for the judicial inquiry to determine what went wrong at the pathology lab between 1997 and 2005.

The tests for estrogen receptors and progesterone receptors are used to help determine if a patient is a candidate for antihormonal therapy, such as Tamoxifen. The erroneous tests meant that some patients were wrongly excluded from being considered for the drug, which has been clinically shown to improve a patient's odds of survival.

Tilley has not finished his testimony, but because of a prior commitment he will be not back on the stand when the inquiry, headed by Justice Margaret Cameron, resumes next week.

Instead, the inquiry will next hear from Louise Jones, who stepped in as chief executive officer after Tilley resigned last July.