The blood type AB positive (AB+) is relatively uncommon, representing only about 3.4% of the population. Individuals with this blood type are known as “universal recipients” for red blood cells, meaning they can safely receive red blood cells from any other blood type. This is due to the presence of both A and B antigens on their red blood cells. While AB+ individuals should donate blood, their plasma is a special component that is significantly more valuable to the blood supply.
Understanding the Unique Value of AB+ Components
Blood type is determined by specific molecules, called antigens, on the surface of red blood cells. AB+ individuals have the A, B, and Rh factor antigens, making them Rh positive. Because their red cells carry all common antigens, their immune system does not produce antibodies against A, B, or Rh.
The plasma component of blood, the pale yellow liquid, is where antibodies are found. Since an AB+ person accepts all red blood cell types, their plasma does not contain the anti-A or anti-B antibodies that attack foreign blood cells. This absence makes AB plasma universally compatible for all patients, regardless of their own blood type.
This compatibility is the reverse of the red blood cell rule: O negative is the universal red blood cell donor, but AB plasma is the universal plasma donor. When plasma is transfused, antibodies within it can cause a severe reaction by attacking the patient’s red blood cells. Because AB plasma is free of these antibodies, it can be given to any patient in need, making it valuable in emergency medicine.
Maximizing Donation Impact Through Plasma
For an AB+ donor, plasma donation is the most impactful way to contribute to the blood supply. This donation is performed using apheresis, an automated procedure that separates blood components. During apheresis, blood is drawn from one arm and passed through a specialized machine that centrifuges the whole blood to isolate the plasma.
The machine collects the plasma into a bag, while safely returning the red blood cells, platelets, and other components back to the donor. This process takes longer than a standard whole blood donation, often lasting between 45 minutes to an hour and a half, but it yields a significantly larger amount of plasma. Donating plasma via apheresis allows AB+ individuals to donate more frequently, as often as every 28 days, compared to the 56-day wait for whole blood.
Universal plasma is heavily relied upon in emergency and trauma situations where there is no time to determine a patient’s blood type before starting a transfusion. It is also used to treat burn victims and patients with severe bleeding or clotting disorders, as the proteins and clotting factors in the plasma stabilize the patient.
Preparing for Donation: General Eligibility and Process
Before donating, all individuals must meet standard eligibility requirements that protect both the donor and the recipient. General health is a primary factor, and donors must feel well on the day of the donation. Donors are required to be at least 16 or 17 years old, depending on the center’s policy, and must weigh a minimum of 110 pounds.
Specific health screenings ensure the donor is safe to proceed, including checking for adequate iron or hemoglobin levels and a brief physical examination. Donors are also screened for certain health conditions, recent travel, and lifestyle factors that could prevent donation. Preparation involves getting plenty of rest the night before and consuming a healthy, low-fat meal and extra fluids before the appointment.
Once at the donation center, the process involves registration, a private health history interview, and a physical check of blood pressure, pulse, and temperature. After passing the screening, the donor proceeds to the donation chair where a sterile needle is inserted to begin the collection. Following the donation, donors are given a snack and fluids to help their body recover.