Several regional public hospitals are under increased scrutiny over higher than predicted death rates of patients.
This is revealed in new information released today by the Health Ministry and the Health Quality and Safety Commission.
The Hospital Standardised Mortality Ratio shows the death rates of hospital inpatients, and those discharged within the past month, are trending down nationally.
But that is not the case for a handful of hospitals, mainly in Gisborne, Whangarei and the Bay of Islands in 2013.
Northland District Health Board said quality there was good, and the data reflected remoteness, relative deprivation and high Maori populations.
The ministry and the commission said the system worked like a smoke alarm - not showing why a result was up or down but triggering further inquiry.
Ministry Chief Medical Officer Don Mackie said the results depended on local details, including the location of a hospital and its case mix.
"I think this is just another measure like a smoke alarm which we can track over a period of time."
Health Quality and Safety Commission director of health quality evaluation Richard Hamblin said the new data could not be used to compare or rank DHBs, or to make simplistic comparisons about quality of care.
He said it would reassure the public about quality.
"I believe it shows a system that has nothing to hide and a system that takes its results and takes its quality seriously."
Dr Mackie said the new method would allow trends to be spotted and prompt discussions with DHBs about investigating any rising trends.