A baby was sent home with the wrong family and three people died after being given the wrong medication in a series of adverse events in WA hospitals, a report has revealed.

Key points: WA is the only state where a baby was released to the wrong family in 2018-19

WA is the only state where a baby was released to the wrong family in 2018-19 It was one of six adverse events in WA hospitals across the 12-month period

It was one of six adverse events in WA hospitals across the 12-month period Two patients had surgical instruments or other material left in their bodies

Data from the Productivity Commission shows they were among six adverse events for the state's public health system during the 2017-18 financial year.

In the remaining cases, two people were forced to undergo further surgery after an instrument or other material was left in their bodies during an operation.

WA was the only state to record an infant being released to the wrong family in that time.

The West Australian hospital involved in the baby mix up has not been identified. ( Flickr: Bridget Coila )

The mistake, termed a "sentinel event" in the report, is not unprecedented in WA, with two cases recorded in the 2013-14 period.

The name of the hospital and other details surrounding the circumstances of the baby's release have not been reported, including how long it took for the error to be realised.

The number of patients who died in WA after receiving the wrong medication was the same as in New South Wales and the second highest of the states and territories behind Queensland, where four people died.

The Productivity Commission defines a sentinel event as one causing "serious harm to patients", which has the potential to "undermine public confidence in the healthcare system".

Push to slash errors 'close to zero'

The former head of the Australian Medical Association in WA, Michael Gannon, told ABC Radio Perth that while events caused by human error eroded confidence in the health system, the public should feel reassured that mistakes were investigated thoroughly.

Two hospital patients had instruments or other material left in their bodies during surgery. ( Unsplash.com: Natanael Melchor, CC-0 )

"Not only do Australian hospitals compare favourably with other developed countries, by most measures -- by cancer survival, by perinatal mortality, by other metrics of true success -- Australia is amongst the safest countries in the world to be admitted to hospital," he said.

Dr Gannon said within hospitals there was a continuous effort to "get these instances down close to zero".

"Those mechanisms where the evidence emerges in Australia or overseas, we adopt it and it comes into our hospitals, whether they be public hospitals or private hospitals," he said.

Western Australia did manage to outperform all states and territories on emergency department wait times, with almost 75 per cent of patients staying for four hours or less.

The proportion of patients waiting for elective surgery for longer than three months fell compared to the previous year, with 9.9 per cent of patients waiting more than 90 days and 3.5 per cent waiting for more than a year.

The final instalment of the Productivity Commission's Report on Government Services 2020 will be released next week.