Thursday October 18, 2001

Everyone's seen pictures of people giving blood; the needle in the donor's arm and the clear plastic bag being carried away. But that's just the beginning. The blood must still go through an intensive screening process before it can be given to a recipient.

Every pint of blood donated in the Tucson area is first sent to the Southern Arizona Red Cross Blood Services center. Upon arrival there, a test tube of blood is packed up and flown on a midnight run to Portland, Ore., to one of the country's nine infectious disease laboratories.

There it is sent through tests for infectious diseases like HIV, syphilis and hepatitis B and C, as well as unexpected antibodies that may cause a reaction in blood recipients. Once the sample is cleared, the data is sent back to the Southern Arizona center via a computer, usually the next morning, and the process can begin.

After laboratory workers eradicate unsuitable blood - they put it in a locked location - they label the good samples and send them to the component lab, where medical technologist Lisa Sharp said, "there isn't a lot of goofing around."

In the component lab, the pint of blood gets placed in a large refrigerated centrifuge, a machine that separates materials in a container by weight by spinning it around a central axis.

The process lasts seven minutes. After that time, the pint comes out in two layers: a clear liquid part that rises to the top, called plasma, and the red blood cells, which fall to the bottom half of the container.

Each drop of blood contains several parts: red blood cells, which is what recipients receive, white blood cells, which are part of the immune system, and platelets, which are used in clotting and plasma. The centrifuge separates red and white cells from the platelets by weight and filters them into separate bags to be processed.

Working in the lab can be stressful, Sharp said. But "you have to find your own enjoyment in it." She said that enjoyment is "knowing that we at the Red Cross have the best blood in the country." Sharp knows this first hand, because she spent 18 years working in a hospital where she experienced that the donation of blood "absolutely makes a difference in surgery."

After they are separated from the plasma, red cells need to be processed again to remove the white blood cells because they have been shown to cause hives and fever in recipients. After that's done, the cells can either be refrigerated for 42 days or frozen for up to 10 years. The freezing process, however, is expensive and labor intensive and is only done to preserve rare types, or blood that only occurs in every one in 1,000 donors.

Someone needs to be in the blood center's lab 24 hours a day to field calls from area hospitals needing blood.

"We need to be there to provide hospitals with any kind of service they need," Sharp said.

Platelets are an important component of blood that have a short shelf life. Used in cancer therapy and for patients undergoing open-heart surgery, platelets are always in demand. But they only last for five days outside of the body. Donating a regular pint of blood only yields a small amount of platelets, but another type of donation - called platelet apheresis - allows for six to eight times the quantity of platelets.

The separated plasma is stored frozen and has a shelf life of up to one year. To respond to the greater number of donors following the Sept. 11 terrorist attacks, the Southern Arizona center has rented a freezer-truck to store more plasma.

The increased number of donors is helpful, said Kay Donohoe, Southern Arizona Red Cross marketing and communications manager. And there can never be too many donors, she said. As medicine improves, the number of blood recipients is increasing. People are surviving cancer, transplants and trauma-related injuries in higher numbers than in the past.

"We'll all sleep better if we have blood on the shelves," Donohoe said. "Because be don't know what tomorrow will bring."