NANNING - Experts are calling on the Chinese government to regulate stem cell transplants after a volunteer donor withdrew at the last minute.

Chen Yuming, 24, from the southern province of Guangdong, was diagnosed with leukemia in April this year, and a bone marrow transplant immediately required.

A matching donor was found from neighboring Guangxi Zhuang autonomous region in July and Chen began chemotherapy in preparation for the transplant.

However, the donor's family got cold feet toward the very end of the procedure and withdrew, leaving Chen in a critical condition until another match was found and the transplant went ahead.

Whether the runaway donor should be under any legal obligation has aroused hot debate among the public: Her final flinch caused a delay of three days to the operation. If no match had been found, Chen could have died at any minute. In the final stages of the procedure, he lacked immunity to almost any disease.

The story has stimulated plenty of discussion on the Internet, with many lashing out at the donor for "showing no responsibility."

"To quit at the last minute in such a case is no different to murder," said one Sina. Weibo microblogger.

Chen's case is only one example of a broader picture in China. In 2005, four volunteers bowed out at the last minute of a bone marrow transplant in Guangzhou, capital of Guangdong.

"They gave me a flicker of hope for survival and then snuffed it out," the patient was quoted as saying.

Behind the chaos about courage and credibility is the worrying situation of bone marrow donation in China.

Potential donors in the China Marrow Donor Program (CMDP) were almost 1.5 million by August 2012, making the marrow bank the world's fourth largest in terms of donors, according to the Red Cross Society of China, but with a demand-supply ration as high as 150:1, China is still in dire need.

The matching ratio between patients and donors is quite low, from 1:400 to as low as one in a million, according to Liu Danli, who leads the data bank of stem cell donors in Guangxi.

Voluntary donation is extremely important in such cases, but a staggering 20 percent of donors eventually bow out. One problem is the misconception that donating stem cells will harm, or even paralyze the donor, said Liu. However, more than 100 donors in Guangxi have got married with children, and nothing has gone wrong.

"If people understood bone marrow donation, the wrong conception would be cleared up," Liu said.

As some questioned whether donors should shoulder legal  responsibilities for reneging, legal experts said that in Chen's case, even though the donor had signed an informed consent before the operation, such a contract allows the donor to withdraw at any time.

"In such cases, unless there are some special provisions, the donor is exempt from any legal liability for breaking the contract, but will surely be condemned by society," said a lawyer with the Baqian Lawyers' Office based in Yunnan Province, who declined to give his name.

Stem cell donation is an unpaid public charity campaign based on people's own wishes, and there are currently no legal provisions in place to regulate it.

Systematic laws and regulations should guarantee the rights of patients, donors and doctors while making their responsibilities clear and definite, said Liu

"The media should promote stem cell transplantation so that the general public will have a better idea of what bone marrow donation is and join the donation campaign," she said.