Alan Roth Sr. has a 30-year habit that helps many people.

Every two weeks, Roth, of Glasgow Village, contributes blood to the Barnes-Jewish Hospital pheresis program. On June 9, he received honors for his 500th donation.

"Naturally, I have good feelings about it," Roth, 73, said. "If your life has been good, then you should give something back to the community."

Pheresis is a method by which whole blood is removed by a machine. The platelets are removed, and then the blood is returned to the body. Platelets are blood cells that prevent bleeding, and the body can replace them in 24 to 48 hours.

Roth is not the only donor in the family. His son, South Side resident Alan "Rusty" Roth Jr., 41, made 300 donations before he was deferred because of arthritis medication.

"I don''t know if I feel heroic," Alan Jr. said. "When I was told I was deferred because of my medication and couldn''t contribute anymore, I felt a sense of loss. I knew I was helping people."

On his 300th donation, Barnes-Jewish officials gave him a jacket. The jacket''s logo draws attention.

"I was in a restaurant and a woman came up and thanked me," he said. "One of her relatives needed platelets."

Alan Sr. experiences similar encounters.

"I''ve had people come up and thank me," he said. "A patient needs platelets, and a donor is the only way to get them."

Resource Nurse Kalpna Shah in the Barnes-Jewish Peresis Department said the Roths are "very nice."

"We develop a friendship with our regular donors," she said. "They get to know us and we know them. Mr. Roth has the most (donations) with 500 visits. We''ve got a couple of donors in the 400s."

Every time the donor reaches another 100 visits, there is a celebration, she said. Barnes-Jewish has about 2,000 donors.

"These donations are incredibly important," Shah said. "Many people really need them to live."

While platelets are used in surgery, they are mostly needed for patients with cancer or leukemia, or those receiving chemotherapy or bone marrow transplants.

Alan Sr. became involved around 1975. Self-employed, he was installing an air conditioner for a nurse. They started talking about the need for blood donors.

"I went and donated blood," he said. "Then I came across a pamphlet concerning pheresis. I went to the Red Cross and took the 50-cent tour. My blood type is O, which makes it the most common."

Alan Jr. started donating in 1983 at his father''s urging.

"Dad told me about it, and I started to contribute," he said. "Actually, it''s been over 300 visits. It''s between 300 and 350. I''ve lost count."

Pheresis donating has evolved. It used to be that donations were matched with patients as closely as possible. Now, while it''s preferable to have a good match, platelets are used for just about everybody.

"We even used to know the names of some of the people who used our platelets," he said. "Now their use is more universal."

If planning to donate platelets, be ready to spend more than an hour, Alan Jr. said.

"It''s easier to donate whole blood," he said. "You can do that just about anywhere. With pheresis, you have to have a special machine that separates the platelets from the blood."

Pheresis locations in St. Louis are at Barnes-Jewish Hospital, Missouri Baptist Medical Center and the American Red Cross.