It is the RH factor of donors' blood that determines who it can be given to. This factor in addition to the blood type, marks the presence or absence of a certain antigen in the blood. Represented as RH negative or RH positive, blood can only be transfused from one person to another if they have the same RH factor.
Amongst Chinese, only three persons in one thousand have an RH negative factor. Therefore those with this blood are said to have "panda blood". But to make it easier for those in need to have this blood, a special volunteer group called the "Rh Blood Home" exists at Beijing's Red Cross Blood Center. Jin Yingqiao has more on this special group of RH-negative blood carriers.
It was in 1989, when Zhou Xuexiang was donating blood that he learned that his blood group had an RH negative factor. He didn't know how rare this was until he was on a visit outside Beijing.
During that time, a patient needed his blood immediately, but the hospital couldn't get in touch with Zhou. He later learned the person had died because the hospital couldn't find a donor with an RH negative factor and it didn't have enough stock in its blood bank.
"It was very sad because there wasn't adequate blood. From then on, I come every year to donate," he said.
Zhou and his fellow donors do what they can, to ensure that the blood they donate is good.
"All the volunteers make sure they keep themselves fit. High quality blood will benefit patients. The hospital will inform us ahead of time if it needs blood. We will prepare by taking adequate rest and avoid drinking alcohol," he said.
Around 200 to 400 ml of blood is collected at a single time. But Zhou insists on donating the maximum amount every time. He doesn't remember how many times he has donated his blood in the past 20 years. But he says what he has done is just normal.
"I just roll up my sleeves and show my love. It's a natural thing and not complicated at all. It's such a good thing to give others a chance to live. I don't think too much," he said.
A simple gesture, but with the potential to save a life.
