There were long-standing issues with the hospital's performance and it was good the Southern District Health Board and the national board were working together to address them.
"This is exactly the kind of role that was foreseen for the National Health Board when it was established," he said in an emailed statement.
One of the ongoing concerns that led to the assessment proposal was access to colonoscopies, something Mr Ryall expressed concern about in October 2009 when general practitioners' worries about this became public.
He called for an urgent report into the situation after claims some patients with possible bowel cancer symptoms were being denied diagnostic colonoscopies.
The number of colonoscopies planned increased as a result, but the board has had difficulty delivering the set number.
At the end of April, Dunedin Hospital was 124 procedures behind the planned 660.
The hospitals' advisory committee has been told a recovery plan is in place.
Labour health spokesman Grant Robertson said he was aware of service issues at the hospital through feedback from constituents and Labour MPs.
Previous systems improvements at the hospital appeared not to have worked in some cases, he said. He suspected Dunedin was the tip of a larger problem with New Zealand hospitals that had been affected by Mr Ryall's "myopic approach" emphasising health targets.
That approach to areas like elective surgery and ED wait times put pressure on resources and might not achieve what it set out to, he said.
National Health Board service improvement manager Jill Lane, who is leading the assessment team, said she had spent yesterday talking to staff.
They had been very welcoming, open and positive, she said.
Association of Salaried Medical Specialists executive director Ian Powell said what little feedback he had received was supportive of the exercise.
Southern board chairman Joe Butterfield said he was comfortable with the process and hoped it would achieve some agreement on what the issues were, particularly with regard to the need for capital development at the hospital.
Chief operating officer (Otago) Vivian Blake expected the assessment would show how "seriously lacking" some facilities were and the impact that could have on efficiency.
She was sure the team would be quite impressed with some of the things it would find.
"Staff do the best they can with what they've got," she said.
• Concerns that led to the assessment include long stays in ED, long radiology waiting lists, booking practices inconsistent with national practice and the level of investment in neurosurgery.
