Platelet donation is a life-saving process, often performed using apheresis, where a machine separates platelets from a donor’s blood. These cell fragments are constantly needed by patients with cancer, trauma, and blood disorders for clotting and to prevent fatal bleeding. A common misunderstanding suggests all females are restricted from donating platelets, but this is incorrect. Restrictions apply only to a specific subset of the female population for scientifically grounded reasons centered on patient safety. These policies relate not to the donor’s health, but to a potential complication that can arise in the recipient of the blood product.
Clarifying the Eligibility of Female Donors
The assumption that women cannot donate platelets is a misconception. Individuals who have never been pregnant (nulliparous women) are generally fully eligible and actively encouraged to donate. Their risk profile for carrying concerning antibodies is similar to that of male donors. Restrictions apply only to women with a history of pregnancy, regardless of the outcome, such as birth, miscarriage, or abortion.
This difference in eligibility exists because a past pregnancy can permanently change the donor’s blood plasma composition. Platelet products collected via apheresis contain a significant amount of plasma, which carries the potential risk to the recipient. This plasma is the focus of current safety guidelines instituted by blood banks. The restriction is a preventative measure to reduce a specific transfusion complication.
The Role of Pregnancy and Alloimmunization
The biological reason for the restriction is a process known as alloimmunization, which can occur during pregnancy. The developing fetus inherits half of its genetic markers from the mother and half from the father. Among these markers are Human Leukocyte Antigens (HLA), which are proteins found on most cells in the body.
During gestation or delivery, a small amount of fetal blood cells carrying the paternally inherited HLA can cross the placental barrier and enter the mother’s bloodstream. The mother’s immune system recognizes these foreign HLA as antigens and mounts a defense. This immune response creates specific anti-HLA antibodies designed to target and destroy the foreign HLA.
Once these anti-HLA antibodies are formed, they remain in the mother’s plasma. This process poses no health risk to the mother herself, but it creates a potential problem for a transfusion recipient. While not all previously pregnant women develop these antibodies, the prevalence is high enough (affecting about one in five) to warrant systematic screening. The resulting plasma, concentrated in apheresis platelet donations, is what carries this risk.
Preventing Transfusion-Related Acute Lung Injury
The presence of anti-HLA antibodies in donated plasma poses a direct risk of causing Transfusion-Related Acute Lung Injury (TRALI). TRALI is a serious complication that occurs within the first six hours of a transfusion and is a leading cause of transfusion-related fatalities.
The reaction is triggered when the donor’s antibodies react with the recipient’s white blood cells (leukocytes), usually in the lungs. This reaction causes the white blood cells to release inflammatory mediators. The resulting inflammation damages the lung’s capillaries, the blood vessels responsible for gas exchange.
Fluid then leaks from the blood vessels into the air sacs, causing acute pulmonary edema. This accumulation of fluid impairs the recipient’s ability to breathe, leading to acute respiratory distress. Restricting certain female donors aims to eliminate these harmful antibodies from the blood supply, preventing TRALI incidents.
Screening Protocols for High-Risk Donors
To manage the risk associated with TRALI, blood centers employ specific screening protocols for female donors. During the health history questionnaire, all potential donors are asked about any history of pregnancy. An affirmative answer triggers additional requirements for the donor’s blood product.
For previously pregnant women, a sample of their blood is collected and tested for the presence of anti-HLA antibodies. This Human Leukocyte Antigen screening is a standard practice that determines the safety of their plasma and platelet donations. If the test returns negative, the woman is deemed safe to continue donating platelets and plasma, often becoming a long-term, regular donor.
If the donor tests positive for the antibodies, she is typically deferred from donating apheresis platelets or plasma intended for direct patient transfusion. However, this does not mean she can no longer contribute to the blood supply. Women who test positive are still fully eligible to donate whole blood or red blood cells. These components are processed in a way that eliminates the risk of TRALI. The plasma from these whole blood donations can be safely used for fractionation, a process that separates plasma into various therapeutic protein products.