The annual death toll of hospital inpatients at the Counties Manukau DHB increased by 51 in five years.
But when measured against the total numbers of patients discharged, the standardised death rate declined and in three years may have bettered the national average.
"We have invested in improvement for quite some time now," said Middlemore Hospital intensive care specialist Dr David Galler.
However, he is wary of making too-strong a link between overall hospital mortality and schemes to improve quality and patient safety.
"You have to have some decent measures as barometers of performance," he said. "Hospital standardised mortality rates are composite measures of organisation performance. It's a gross measure."
The board's clinical director of quality improvement, Dr Mary Seddon, said standardised in-hospital mortality rates were of no use in measuring quality as only a small proportion of hospital deaths were preventable.
As well, risk adjustment calculations did not include some factors, such as smoking and obesity, that affected mortality.
Since his appointment in 2006, chief executive Geraint Martin has fostered development of a culture of healthcare innovation and quality, especially with the creation of Ko Awatea - the board's health education and research centre - in partnership with the Massachusetts-based Institute of Healthcare Improvement.
Ko Awatea, the institute and the Health Quality & Safety Commission are this week running a conference in Auckland on healthcare improvement.
The institute was the source of a now-widespread infection control scheme introduced at Middlemore Hospital in 2008.
Dr Seddon said in the NZ Medical Journal at the time that it usually took 17 years from a clinical process being proven effective, to it becoming established as common practice.
Dr Galler said that time could be cut if health workers were actively encouraged to take responsibility for the change, as had happened with the central line-associated bacteraemia anti-infection project.
"We've owned it. It has been around for a long time internationally. We were quite slow to adopt it. Our progress came when we began to own the work as ours."
Five years of hospital death rates have been made public for the first time - in the Herald. We compare health boards, investigate where lives are being lost and the battle to save them.
Monday - District health boards compared, is death rate linked to healthcare quality, and how a simple checklist helps surgeons to avoid mistakes.
Tuesday - Waitemata DHB boosts heart-care capacity. A bereaved father questions medical justice.
Wednesday - Waikato DHB strives to understand its high death rate, medication safety, and a doctor's apology.
Yesterday - Palliative care helps Auckland DHB's good performance. A widow fights for changes.
Today - Obesity skews the statistics in South Auckland. Lives saved by reduction of blood infections.