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A technologist looks for clumping in a blood transfusion test (Photo: Michael Ronchka)

In the often-hectic UHN blood transfusion laboratories, technologists with expert knowledge make sure blood and blood products are safe for patients, one unit at a time.

We visited the 'heart' of UHN to learn what happens to blood donated to Canadian Blood Service (CBS) before patients receive a transfusion.

The heart of UHN

The blood transfusion laboratory at UHN serves Toronto General Hospital, Princess Margaret Cancer Centre and Toronto Western Hospital. Although it's no bigger than the main floor in an average suburban home, all 125,000 units of blood, plasma, platelets and other blood products used at UHN every year move through the transfusion labs — enough blood to fill a swimming pool. On any given day the three blood banks have over 1,600 units available for patients going to surgery, being treated for cancer or other conditions requiring a blood transfusion.

The transfusion lab has state-of-the-art  automated blood-typing machines that can perform dozens of tests at once, but most of the work in the blood bank is still very hands-on — requiring a centrifuge, test tubes, pipettes and most importantly, expert knowledge of transfusion medicine  and transfusion laboratory science.

The science of transfusion medicine is used to match blood to each patient's need. Packed red blood cell donor units and other blood products are delivered by CBS daily. They are stored in the kind of refrigerator you might see in a convenience store, except it has temperature tracking devices and alarms to alert the staff if the temperature gets too warm or too cool. 

Transfusion lab manager Sally Balmer doesn't like the sight of blood, unless it's neatly organized and labelled in test tubes or bags. She started in the transfusion lab part-time 32 years ago while training to become a medical laboratory technologist and has since worked her way up to become manager of the Blood Transfusion laboratories, part of the Laboratory Medicine Program (LMP).

"It's fine right now, but when four different ORs call down for blood at the same time it gets hectic," said Balmer, as she tours us around the lab. "The staff must be focused because their work requires accuracy, but they also have to listen to the communication around them to make sure all requests are being filled in priority. It's stressful, but when you go home, you know you've helped save lives."


For a blood transfusion to work, it's not enough for the donor and recipient to share the same ABO and Rh blood types. Red blood cells have hundreds of markers called antigens that could trigger a response from the immune system. The blood transfusion lab routinely checks recipients for antibodies, proteins that fight off foreign substances in the blood, made against the top 20 most common antigens. 

"If a patient has no antibodies, we can process an order in as little as ten minutes once the group and screen testing is complete. For patients with antibodies, the process can take three or four hours to several days or weeks depending on how many different antibodies they have," said Balmer. "We work very closely with CBS, and they will fly in blood from another part of the country for patients with many antibodies."

Antibody detectives

The technologists in the blood transfusion lab test for antibodies by mixing a blood sample with a reagent containing known antigens then watch to see if it clumps.

After detecting antibodies, technologists identify exactly which ones the patient has by process of elimination, testing antigens in smaller and smaller groups until they know precisely which antibodies are in the patient's blood.

"Along with routine techniques, we are using red blood cell genotyping profiles for patients with conditions such as sickle cell disease who require regular, lifelong transfusions," said Balmer. "Our technologists work with our doctors, called transfusion medicine specialists, to ensure we deliver the best product. Every unit gets thoroughly tested and crossmatched before reaching our patients. This is very much a team effort that requires constant vigilance as new emergencies arise."   

"It's always hectic in the transfusion lab and it's always painstaking work," added Balmer. "Our team knows that a mistake in blood transfusion could cost lives. But, our expert staff enjoy the challenge and we know we're working hard for our patients."

The Inter-Hospital Blood Drive Challenge

The Inter-Hospital Blood Drive Challenge has ended and the results are in: Toronto General Hospital placed third overall with 91 blood units donated. Toronto Western Hospital staff donated 47 units; Princess Margaret Cancer Centre, 33; and Toronto Rehab, 29.

​To find out who won and for the complete results, click here.​​​

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