Health Minister Jonathan Coleman has ordered an investigation into alleged "manipulation" of data at district health boards to comply with the six-hour emergency department target.
The first study on this since the six-hour target was introduced in 2009 was presented at a Queenstown conference today by Dr Peter Jones, an emergency medicine specialist and Auckland University researcher.
He said he had found evidence that the data had been manipulated to meet the target.
Opposition politicians have long suspected this, especially after widespread manipulation was uncovered in the UK to comply with its tighter, four-hour target. The UK's policy, unlike in New Zealand, came with incentives and penalties.
Coleman, whose predecessor Tony Ryall introduced the six-hour target, said tonight: "I'm assured that the integrity of the health target data is sound. No issues around manipulation of the ED target have been raised with me. I've asked officials to investigate this claim further."
Jones gathered data on ED patients' lengths of stay at four unnamed district health boards from 2008 to 2012. A co-researcher interviewed key staff.
Jones said he had told the ministry of his findings, although it was only in the last 12 months that the research data had been analysed.
The target is that 95 per cent of patients will be transferred, admitted to a ward or discharged within six hours.
On Monday, Jones told the conference about 700 fewer patients had died in EDs in 2012 than would have been expected if pre-target trends had continued. The death rate had dropped by 57 per cent after adjusting for age, ethnicity and deprivation.
Today, he said there had been an increase in the percentage of patients who left the ED after being there for exactly six hours.
"In the natural flow of things, a certain percentage would be leaving at six hours. With the target that jumped up 5 per cent [at one study DHB]."
The range was from around 2 to 5 per cent.
I was told by an emergency department themselves the things they did to ensure that they didn't go over the six hours
"We found across all the sites there was some evidence of data manipulation. It occurred most in sites that weren't adequately resourced to match the pressure put on staff in DHBs to meet the target.
"It wasn't black and white - or all or none. We just saw a trend towards more evidence of potential data manipulation where pressure to meet the target wasn't matched by resources."
His group has previously established that DHBs spent $52 million hiring more ED staff and improving hospital processes to meet the target, but they had to shuffle budgets to do this because the Government provided no extra cash.
"Things got better on the whole despite the data manipulation and gaming that we saw ... It's not a problem if patient outcomes are improving."
He said there was some evidence short-stay units were used to "stop the clock", but arguably that didn't matter because it was a more-private environment with its own nursing staff, making it better than being left "in a corridor on a hard bed, with no privacy - the sort of thing we wanted to fix with the target".
Labour's health spokeswoman Annette King said it was well known in the sector that gaming and data manipulation occurred, but when she had asked about this at the health select committee she had been told it was untrue.
"I was told by an emergency department themselves the things they did to ensure that they didn't go over the six hours."