Blood Donations and the Science that Keeps Us Safe

January is National Blood Donation Month. According to the Red Cross, an individual saves ~3 lives by volunteering to have blood drawn and donated! Winter, unfortunately, is often a time of blood shortages with both the holidays and cold/flu season slowing down donation rates. Blood banks and doctors are hoping that this year will be a different story as blood supplies are already at a historically low level. Several public awareness campaigns are underway and we’re joining in! Read on to learn about the biotechnologies that ensure safe blood donations.

Blood donations begin with a mini-physical for the donor. The donor’s age (17+ in most states), weight, and height are determined. Their pulse, blood pressure, and body temperature are taken. Finally, blood tests that measure the proportion of red blood cells in the blood (hematocrit test) and the level of hemoglobin in the blood (hemoglobin test) are administered. All this allows the nurse to determine if the volunteer can give blood without becoming temporarily anemic.

A technician secures several test tubes filled with blood during a drive in New Orleans. Vegasjon, CC BY-SA 4.0 <;, via Wikimedia Commons

In addition, the donor is asked a series of questions to check that their blood is likely safe for transfusion to a patient. For example, donors are asked if they take certain medications that linger in the blood or have recently visited certain countries where diseases like malaria and vCJD are prevalent. (The absence of these diseases is also confirmed later by lab tests.)

If a donor ‘passes’ both the physical and questionnaire screenings, blood is drawn. This process usually takes about 5-10 minutes. While the donor recovers (often with the help of a juice or cookie), the donated blood, samples of the blood, and the screening results are labeled with identical bar codes and taken to the nearest processing centers and analysis labs.

At the processing center the blood donation, sometimes called a whole blood sample, is centrifuged. This separates the sample into several different lifesaving components including red cells, platelets, and plasma. Each component has different storage conditions, shelf life, and medical uses.

  • Red blood cells (RBC) can be stored in a refrigerator for up to 42 days and are given to patients with significant blood loss due to trauma or surgery or to patients with sickle cell anemia.
  • Plasma, the liquid portion of blood, is stored in the freezer for up to a year and can help stop bleeding. Plasma transfusions are used to help patients with severe infections, serious burns, clotting disorders, and liver failure. They are also given to patients undergoing chemotherapy.
  • Platelets are stored at room temperature with constant agitation. They only last a maximum of 5 days. Platelets are needed for patients undergoing organ transplants, open-heart surgery, and chemotherapy.  

Meanwhile, at the lab, technicians analyze donated blood samples. One of the most important tests is to confirm blood type. Humans have four main blood groups (A, B. AB, and O) and can be RhD negative or positive, so there are 8 major blood types. Receiving blood from a compatible type is essential. Our immune systems are constantly looking for ‘non- self’ cells and molecules in the blood and will reject and fight non-compatible blood transfusions.

In addition to typing, the donated blood is screened for the presence of viruses (like Hepatitis B Virus and HIV) and other harmful pathogens (such as Trypanosoma cruzi, which causes Chagas disease, and Treponema pallidum, which causes Syphilis). These are identified using a combination of enzyme-linked immunoassays (ELISAs) tests and Polymerase Chain Reaction (PCR) tests. The Red Cross has detailed information on the current tests it uses here.

Once blood donations are judged to be safe for transfusion they’re shipped to hospitals. 

It’s estimated that in the US someone needs a blood transfusion every 2 seconds. However, the pandemic has deterred donators and US blood supplies are critically low. If you’re interested in donating find out about the eligibility requirements (here) and then find a blood drive near you (here)! If you’re interested in incorporating the biotechnology of blood donations into your classroom, check out the resources below!

Resources for Teaching about Blood Donation  

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