Dr. John Cowell of the Health Quality Council says there was no thorough hiring process in place at the Royal Alexandra Hospital when a temporary pathologist was hired a year ago.
It was subsequently found the pathologist either under-reported the level of cancer or missed cancer altogether in 159 samples.
"We felt the hiring process for the (temporary) was too casual," Cowell told a news conference in Calgary.
"We felt an inadequate background check was done and an (inadequate) review of that particular individual's work.
"There was an assumption because that individual had already been a successful, privileged pathologist, that the person would have automatically been competent to do the (prostate sample) work they were being assigned.
"This pathologist historically was not reviewing that many prostate samples, but in this job was doing significantly more interpretations than had been the experience in the past."
Cowell's team compiled the report after he was directed to undertake the investigation a year ago by Health Minister Fred Horne into problems with tissue samples at the Royal Alexandra Hospital and at Calgary's Rockyview Hospital.
Both reviews found the patients affected were not harmed.
Cowell said his team found problems with 31 tissue specimens in the lab at Calgary's Rockyview Hospital because the tissue testing machine did not abort a test if the technician made a mistake.
"If (the technician) put the wrong fluid in (or) didn't put the right fluid in one of the chambers the machine would still go ahead and process. Alarm bells wouldn't go off," said Cowell.
"If you're going to be using machines like that, you need to have very strict processes in place so you avoid human error."
He suggested new protocols to allow staff work to be double-checked before the machine runs the test.
The mistakes were made at the Calgary Laboratory Services Diagnostic and Scientific Centre, located in the Rockyview.
The lab is wholly owned by Alberta Health Services, which runs the day-to-day operations of the provincial health system.
Cowell said along with the machine problem, the tissue mix-up exposed administrative problems and that it was unclear who was to report to whom.
He also said there was not a clear process in place when the patients with the misdiagnosed tissues had to be told.
"Some patients were informed, for example, just before Christmas, and they were informed in a way that was confusing to them and that created huge stress at a very critical time of year," he said.
Cowell said Alberta's College of Physicians and Surgeons needs to take a stronger hand in making sure pathologists are properly trained and that information is passed on to the clinics, labs, and hospitals.
He made seven recommendations and Alberta Health Services says work is underway to implement them all.
On Wednesday, the College and Horne said that change is also underway after a separate report revealed a wide discrepancy from region to region on what pathologists are permitted to do.
"When you look at both reports what it says to us, I think, is we need to do a better job of documenting critical information, what privileges doctors have and on what basis, (and) making that information more readily available," Horne said.
Opposition Wildrose Leader Danielle Smith says the government needs to fix the reporting channels, citing an early Health Quality report that detailed how some health professionals were reprimanded or even fired for bringing problems forward.
"This is exactly the reason why we've called for a full public health inquiry because these are the kinds of things that our health care professionals are trying to bring forward," said Smith.
"They're getting stonewalled on it, and unfortunately we've put patient health at risk."
Liberal Leader Raj Sherman said the problem lies with the constant reorganization of the administration, including the 2008 amalgamation of all regional boards into one superboard.
"The government has had so many management shuffles that as a frontline health care worker, sometimes you wonder who's in charge," said Sherman, who is also a physician.
"When you don't have leadership that's stable, these kind of mistakes are going to happen."
Horne called for province-wide review of all diagnostic imaging and pathology testing last Dec. 29 after the Edmonton and Calgary cases came to light along with a case of misread CT scans at the Drumheller Health Centre.
Alberta Health Services investigated and found problems with one in every 10 CT scans done in 2011 at the Drumheller centre.
Fifty ultrasound studies and 49 X-rays were also checked, with problems found in one X-ray.
The radiologist involved no longer interprets CT scans, but still checks X-rays and ultrasounds.