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He revealed yesterday he told both the board and the Ministry of Health in June last year the service was under significant pressure.
It was not clear in the particular case before him, however, that access was worse than in other parts of the country at that time.
He said the situation, as described by South Link Health executive director Prof Murray Tilyard in his October letter to the Otago District Health Board, was very concerning and he was not surprised Health Minister Tony Ryall had called for an urgent report.
What was concerning about the reports of individual cases and comments reported by GPs in the coverage of the issue was that they appeared to have been advocating without success for their patients.
The situation needed urgent attention.
"I agree with Prof Tilyard that we won't know if this is the tip of the iceberg without an audit of all referrals for the colonoscopy clinic and I trust the Southern Cancer Network audit and review will be thorough and comprehensive.
"It appears this would be needed to reassure patients, clinicians and the public of Otago."
Board chief executive Brian Rousseau said the initial audit would involve the referrals listed in the letter from Prof Tilyard.
If the audit showed that people who had died should have had a colonoscopy and would definitely have lived had they had one, then a wider audit would be needed.
He emphasised again the cases raised by Prof Tilyard had to be considered as anecdotal at this stage.
Until checking was complete there was the risk of "creating a hell of a storm in a tea cup" which could mean "everybody can look pretty bloody silly at the end of it".
He confirmed the board was still waiting for national health index numbers to identify some of the patients about whom GPs had raised concerns.
So far, only 25 numbers had come in to oncologist Shaun Costello, who would refer them to the Southern Cancer Network.
Dr Costello said the key question was whether a colonoscopy would have made a difference.
There was fairly robust prioritisation criteria which the cases would need to be judged against and there was a " whole chain of things" which happened before patients were prioritised.
Prof Tilyard's survey of GPs listed 51 patients about whom doctors were concerned, including 25 patients they said had been refused colonoscopies and were later found to have cancer.
Mr Paterson made his comments in response to a query from the Otago Daily Times about whether he had received any complaints over access.
Mr Paterson said he received a complaint in January 2008.
After investigation, he raised concerns with the health board and the Ministry in June.
Mr Paterson did not divulge details of the complaint which prompted his concerns, but the Otago Daily Times has established through other sources the complaint was made by a woman in her 40s who had surgery for bowel cancer in 2004.
In 2007, she was concerned about symptoms possibly indicating a recurrence of the cancer and was referred by an oncologist at Dunedin Hospital for a colonoscopy.
She waited three and a-half months for an appointment with a gastroenteroloy specialist and was not given a date when she would get a colonoscopy.
She was concerned about the "lack of clear process" and being left in limbo with concerning symptoms.
The board's decision not to offer colonoscopies in accordance with the national surveillance guidelines for those considered at increased risk of colorectal cancer was also questioned by the woman.
Although she was concerned about her own situation, she was also keen to see others in similar circumstances receive more timely access.
She felt the board needed not only to acknowledge the problem but be serious about solving it.
Her colonoscopy, which was clear, had been carried out by the time Mr Paterson wrote the letter to the board.
Mr Rousseau said there were long waiting times for diagnostic colonoscopies in 2007, which was why the decision had been made not to offer routine surveillance to those considered at increased risk according to the national guidelines.
At the time of the woman's complaint, the service was still dealing with the tail-end of a huge number of referrals.
The woman's case had been prioritised, along with everybody else.
When a service was being rationed because of staffing constraints, it could not meet the total demand.
He agreed there were potentially issues of clinical safety with any service which could not meet the demand.
Comment from the Ministry of Health on its response to Mr Paterson's letter was not available yesterday afternoon.
