Where do you fit in the blood system?

Published on October 18, 2012

Every day, Canadian Blood Services (CBS) is challenged with a difficult task: balancing the blood system.

Michelle Rogerson, director of product and hospital services for CBS, calls it the “Goldilocks effect.” You certainly don’t want too little blood, but you don’t want to take too much of it, either — especially too much of the wrong kind.

“In Newfoundland, we have whole blood collection, we have apheresis plasma collection and we have apheresis platelet collection, so we pretty much have the full gamut,” she said. “Knowing the blood group of the donor would perhaps influence which type of donation we would prefer to collect.”

Apheresis refers to a process by which a specific component is extracted from the blood during a donation.

Like any blood system, Canada’s is very complicated.

There are four main blood groups: O, A, B and AB. Each of these can have either a positive or negatve Rh factor.

Canadian Blood Services works closely with hospitals to determine how much blood will be needed, and organize donations based on that.

“We can get a really good idea of what demand is by doing modelling and forecasting based on previous years,” Rogerson said. “But, for example, if there’s a new cancer care facility that starts up in the city, then obviously that’s going to change the demand pattern, so we may have to adjust our collection patterns to suit that as well.”

Group O-negative blood is the universal blood type, which means it’s always in demand.

“I don’t think I’d ever say we’ve had too much O-neg,” she said. “I think we’re further ahead than we were five years ago, but we still don’t have as robust an O-neg inventory as I would like to see.”

Donors with O-negative blood are best giving whole blood. Just seven per cent of Canadians are O-negative, making donors with this blood type particularly precious to the blood system.

Doctors in hospital TV shows such as “Grey’s Anatomy” demonstrate how O-negative blood can be crucial in emergency situations.

“They’ll say, ‘Ten units O-neg, stat to the OR!’” Rogerson said.

Solid stock

Smaller hospitals that keep little blood in stock always have a solid stock of O-negative blood because it can be used by any patient when there isn’t time to test for blood type.

Dr. Lucinda Whitman, divisional chief for laboratory medicine (hematology) for Eastern Health, said because O-negative cells don’t have have any A or B antibodies, which would kill the new cells, Type O blood can safely be transfused to a patient of any blood type.

“Those red cells are the least likely to cause reaction in the patient who gets them, so it can go to any blood group,” she said. “Some transfusions are an emergency thing — you know, someone who’s been in a car accident, for instance, may need blood and they need it really fast.”

Hospitals keep a supply of blood on hand, based on predicted needs. When a situation isn’t urgent, however, blood type is tested prior to transfusion.

“When a patient comes in and they’re going to need blood, first of all the responsible physician orders the blood and it could be any one of a number of different blood products that we stock within the hospital,” Whitman said. “Then the order comes to the blood bank with a sample from the patient, and we match up the right blood component for the right patient.”

High demand

Blood type AB donors are also in high demand, but, unlike group

O-negative donors, it’s not red blood cells CBS is looking for.

“The plasma from an AB person can go to an A person, a B person or an O person,” Whitman said.

Because of this, Type AB donors are best used in the plasma program. Just three per cent of Canadians have Type AB blood. Plasma donors can give once a week — more frequently than whole blood donors.

“AB plasma is the blood group of choice for plasma transfusions,” Rogerson said. “And that’s a very rare group.”

Groups A-positive and O-positive are the largest blood groups, and they both have relatively constant supply and demand. Most donors in these groups are best off giving whole blood.

“O-pos would be the most prevalent blood group in patients, so therefore we would need more

O-pos,” Rogerson said.

An overwhelming 39 per cent of Canadians are Type O-positive. Their blood can be used by any person with a positive Rh factor.

“Therefore it would make sense that it would be the highest in demand on a regular basis,” she said.

The same goes for group A-positive — about 35 per cent of Canadians fit in this blood group.

Though the need is great, blood from A-positive donors is compatible with fewer blood types than that of O donors.

Type A platelet donors are also needed, as they can donate to patients in both group A and group O. If you have a high platelet count and your blood type is A-positive, there’s a good chance CBS will encourage you to donate platelets.

Though Canadian Blood Services is in constant need of blood, somtimes donors want to give more than is needed.

“We don’t want to outdate products. We don’t want to have too much,” Rogerson said. “We just want to have exactly what we need to meet patient demand.”

CBS usually has a higher inventory of B-positive blood, meaning these donors are not as high in demand as donors of the other blood types. The demand is simlar with B-negative blood. As the second-smallest blood type in Canada, fewer donors are required.

B donors are best used giving whole blood, but only once or twice a year, rather than more regularly. Even if a donor wants to come in each time they’re eligible — every 56 days — CBS doesn’t want to take a person’s blood if it’s not going to be used.

“It’s a hard message sometimes, because they feel that you’re encouraging them not to come in, so it’s how to balance that well,” Rogerson said.

Type B donors who want to give more frequently could also donate plasma.

CBS doesn’t turn donors away, but works with them to find where their donation can be best used to save lives.

Rogerson said she often tries to encourage donors by saying, “If you give red cells — or whole blood donation — three times a year, this is what it might mean to a patient.”

The Telegram is encouraging people to head down to the Canadian Blood Services clinic at 7 Wicklow St. in St. John’s to help reach the goal of 250 blood donations for the annual The Telegram Saves Lives week.

The clinic is open today from

11 a.m. to 7 p.m. and Friday from

9 a.m. to 1 p.m.