Hong Kong public hospitals are using sophisticated DNA sequencing to pinpoint poisonous species of wild mushrooms to avoid unnecessary tests and cut costs.

Hospital Authority toxicology reference laboratory consultant Dr Calvin Chong Yeow-kuan explained on Wednesday that hospitals would sometimes have no idea what type of mushroom had caused poisoning if a patient was unconscious or failed to tell doctors they had eaten them.

He added mushrooms could also be unidentifiable when they had been cooked, diced, or where they belonged to a species rare in Hong Kong.

“This service allows our clinical doctors to be more confident in treating the patients and take fewer wrong turns when identifying the mushrooms,” Chong said.

“It provides us additional information about the poisoning on top of using traditional methods. When we can identify the exact type of fungus, we can inform our citizens and government so that they can make improvements to the situation.”

Chong highlighted that the technology offered precise identification, which saved time and expense.

Hospital Authority toxicology expert Dr Calvin Chong says DNA sequencing can identify wild mushroom species that cause poisoning in patients.

He said there were more than 380 types of fungi in Hong Kong. Most are inedible and around eight to 10 cases of mushroom poisoning are recorded each year.

Most cases involve people eating mushrooms they had gathered in the wild.

Conventional methods used to identify a mushroom species include symptoms displayed by the patient, identification by fungi experts, or urine or blood tests, with an accuracy of 70 to 80 per cent.

Chong, also a consultant in the Princess Margaret Hospital pathology department, said the usage of polymerase chain reaction tests in DNA sequencing was introduced internationally in 2012.

Princess Margaret Hospital started to use DNA sequencing on mushroom samples or stomach acid of patients suffering from poisoning in 2018. The testing service was made a regular feature in public hospitals from 2020.

Chong said, after the DNA sequence of the mushroom was isolated, they would compare it with sequences logged in international databases to work out the type.

He added treatment for mushroom poisoning was mostly determined by patient symptoms instead of by species, except where fuligineoides were involved, which need an antidote.

But, after DNA sequencing confirmed that a mushroom was not fuligineoides, doctors could stop use of the antidote.

“I don’t think this kind of technology is widely used in most of the hospitals [overseas] … we are fortunate to have this opportunity because in other countries, many of the toxicology laboratories are not manned by pathologists,” Chong said.

“We already have genetic and genomic pathologists … and we have ready access to this technology.”

A middle-aged woman suffered sweating, vomiting and diarrhoea last September after she ate a bag of wild mushrooms gifted to her by a stranger during a hike, but the initial examination could not identify the species.

But DNA sequencing found that the mushroom was very similar to a species discovered in Hainan in mainland China in July that year and contained the same poisonous substance.

Another food poisoning case was logged last December after the patient became ill after eating an unknown plant, but urine tests failed to isolate the plant species.

DNA sequencing showed that the plant was jícama, which has edible roots, but the rest of it is toxic.

“In the future, we are planning to use the technology to improve the situation of patients who are poisoned after eating plants,” Chong said.

He added Hong Kong was at present using first generation technology, which could only identify a mushroom species if one type was eaten.

“If a number of different mushrooms were diced and made into a soup, the second-generation DNA sequencing is required,” Chong explained. “It was introduced to all clusters last year but has not been used.”

He added that doctors also wanted to introduce third generation technology to boost testing speed.

Chong was one of the winners at the Hospital Authority's Young Achievers Awards this year. He was honoured for his work on the clinical application of mathematics and information technology.