Indigenous Australians suffer “implict racial bias” when presenting for hospital treatment, a coronial inquiry into the death of Naomi Williams has heard.

The Indigenous caseworker died of a treatable infection at a small rural hospital in New South Wales in 2016.

She was six months’ pregnant when she presented to the emergency department of Tumut hospital with severe pain, but was sent home after 34 minutes with two paracetamol and without seeing a doctor.

The 27-year-old Wiradjuri woman’s condition worsened and 15 hours later she died from sepsis associated with the bacterium Neisseria meningitidis.

At an inquest in Sydney, the deputy state coroner Harriet Grahame asked an expert whether Williams’s Indigenousness played a part in her poor treatment.

Williams, a Naidoc award-winning disability caseworker, had already visited the same hospital 18 times in six months, and two doctors told the inquiry previously she should have been referred to a specialist.

“Naomi Williams went to the doctor many, many times and never got a specialist referral,” Grahame said on Thursday. “If I look at it from my own experience as a middle-class woman in the eastern suburbs in Sydney, my perception is I would have gotten a referral. I wouldn’t have gone 18 times and not gotten a referral.”

Prof Yin Paradies, an expert in race relations and public health at Deakin University, said hospitals generally suffered from implicit racial bias that meant Indigenous patients received worse levels of care.

“The best data we have in Australia is there are 30% fewer procedures for Aboriginal patients across the country compared to non-Indigenous patients,” he said. “And that is accounting for where the patients live, socioeconomic status, marital status, gender and age.”

Naomi Williams went to Tumut hospital in severe pain, but was sent home after 34 minutes without seeing a doctor. Photograph: Sharon Williams

He said Indigenous patients were discharged from hospital, against doctors’ advice, at a rate five times higher than non-Indigenous patients.

“There is a strong correlation between treatment and Aboriginality,” Paradies said. “There is evidence of stereotyping Indigenous people as more likely to use drugs and alcohol and so that sort of stereotype is very likely to be present in the minds of many Australians, given its pervasiveness.”

Williams had told medical staff she occasionally used marijuana to cope with severe pain, and was repeatedly referred to drug and alcohol services, despite reports saying she had no dependence on the drug.

And earlier on Thursday, the inquest heard from a microbiology expert, Dr David Andresen, who said the antibiotics to treat Williams would have been readily available in a hospital like Tumut.

But he said there was a 5% risk that antibiotic treatment would not have saved Williams. “There are some patients who are too sick at presentation to be saved by antibiotics,” he said.

The inquest also heard that in September 2018, the percentage of the Tumut hospital workforce that was Indigenous was 2.3%, compared to the local population being 5%.

“It also does matter what sort of jobs they are,” Paradies said. “You want doctors, nurses, people at all sorts of levels and areas.” He also said hospitals needed to address the issue of gender imbalance in Aboriginal health workers.

Outside court, Paradies told media there was evidence that showed broadly how a level of mistrust had emerged between hospitals and Indigenous patients.

“Historically, we had the stolen generations ... in hospitals there have been a history of forced sterilisation and babies being taken and so on, within hospital settings.

“We have evidence that the actual identification as an Aboriginal person in hospital leads to worse treatment. Which is problematic because a lot of effort in hospitals is around better identification of Indigenous patients.

“What can happen is assumptions that Aboriginal people have drug and alcohol issues. There could be serious investigation into that. But it can be the wrong avenue to go with because there is no indication for that individual that it is a problem ... sometimes it’s not about apathy it’s about investigations along the wrong path.”