This is the VOA Special English Science Report.
People all over the world know the importance of giving blood to help people who have lost blood because of an accident or operation. There is also a need for the part of the blood called platelets.
Platelets are cells in the blood that help stop bleeding by permitting the blood to become thick, or clot. Taking platelets from a person’s blood is done in a process called apheresis (a-fur-ee-sis).
Blood is taken from a blood vessel in a person’s arm through a tube. The blood is passed through a machine called a centrifuge. The machine separates the platelets from the other parts of the blood and collects them. The machine returns the other parts of the blood to the person’s arm.
This process takes about two hours. A person’s body replaces the donated platelets in about forty-eight hours. One person can give platelets up to twenty-four times a year.
Almost all healthy people can donate their platelets. A person must be older than seventeen years of age and weigh at least fifty kilograms.
However, some people with medical conditions should not donate platelets. People should not donate platelets if they have ever suffered hepatitis or cancer or have heart problems. People should not donate platelets if they have had malaria or lived in an area where the disease is present in the past three years.
Women who have been pregnant in the past six months should not give platelets. Blood donation programs also will not accept blood products from people who may have been infected with the AIDS virus.
And the programs will not accept blood products from people who have visited countries where mad cow disease is present.
Blood centers always need platelets because donated platelets must be used within five days. People who are having treatments for cancer need blood platelets. Radiation and chemotherapy treatments lower the number of platelets in their blood. So they must get platelets to prevent bleeding.
Experts say the demand for platelets continues to increase as more people are getting cancer treatments. The strong government controls to guarantee the safety of blood products have also limited the supply of platelets in recent years.
This VOA Special English Science Report was written by Nancy Steinbach.