Platelets are small, disc-shaped cell fragments in the blood that are necessary for stopping bleeding (hemostasis). They function by aggregating, or clumping together, at the site of a blood vessel injury to form a plug, preventing blood loss. Patients undergoing cancer treatment, organ transplants, or major surgery, as well as those with severe trauma, often require transfusions of healthy platelets to prevent life-threatening hemorrhage.
Unlike a whole blood donation, which collects all blood components simultaneously, platelet donation uses a process called apheresis. This automated procedure draws blood, separates the platelets using a centrifuge, and returns the remaining blood components to the donor. Because the eligibility requirements for this specialized donation process are more specific than for whole blood, many potential donors find themselves temporarily or permanently deferred.
Baseline Physical and Blood Requirements
Apheresis donation necessitates strict physical and hematological standards to ensure the safety of both the donor and the recipient. A minimum weight of 110 pounds is required, as this measurement is used to calculate the safe volume of blood that can be processed during the apheresis procedure. Donors must also meet a minimum age requirement, which is 17 years old in most locations.
The donor’s overall blood health is assessed through specific blood tests performed just before the donation. A minimum baseline platelet count is required to ensure the donor maintains a sufficient level of platelets after the donation is complete, preventing excessive post-donation bruising or bleeding.
The donor must also meet minimum hemoglobin and hematocrit levels. These measurements confirm that the donor has an adequate number of red blood cells to safely withstand the temporary loss of blood volume during the apheresis process.
Medications That Affect Platelet Function
One of the most frequent reasons for platelet deferral is the recent use of medications that interfere with platelet aggregation. These antiplatelet agents disrupt the ability of platelets to stick together and form a clot, which renders the donated platelets ineffective for a transfusion recipient. This deferral is based on the quality of the product.
Common over-the-counter pain relievers like aspirin and any medication containing acetylsalicylic acid are the most well-known culprits. Because aspirin irreversibly inhibits a platelet’s function for its entire lifespan, donors must wait at least 48 hours after the last dose. Some non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen may also require a deferral period, typically 24 hours.
Prescription antiplatelet drugs used to prevent strokes or heart attacks, such as clopidogrel (Plavix), require a longer waiting period, often 14 days. The deferral period varies depending on the drug’s mechanism and how long it remains active in the body. Taking these medications usually only prevents platelet collection, not whole blood donation.
Recent Exposure and Infection Risks
The blood supply must be protected from transmissible diseases, leading to deferral criteria related to recent exposures and infections. Donors experiencing symptoms of a cold, flu, or any other illness accompanied by a fever are deferred until they are symptom-free for a specified period, often 24 to 72 hours, to prevent transmitting an infection to a vulnerable patient. This includes individuals who have recently completed a course of antibiotics for an active infection.
Procedures that involve breaking the skin barrier can introduce the risk of bloodborne pathogens, such as Hepatitis B, Hepatitis C, and HIV. Therefore, receiving a tattoo or body piercing may result in a temporary deferral of three months if the procedure was not performed in a state-regulated facility using sterile needles and ink. This waiting period allows time for the body to develop detectable antibodies to these pathogens.
Travel to areas where certain infectious diseases are endemic also creates a deferral. For example, travel to regions where malaria is common may require a waiting period, typically three months, even if the traveler took preventive medication. Similarly, travel to areas with active outbreaks of specific viruses, such as Zika, can lead to temporary deferrals to ensure the safety of the donated product.
Logistical and Scheduling Constraints
A potential donor may be deferred due to constraints related to the donation process itself. The apheresis procedure requires drawing and returning blood through a needle, which necessitates adequate and accessible veins (good venous access). If a donor’s veins are too small, fragile, or difficult to access, the apheresis machine may not be able to perform the donation successfully, leading to a deferral.
A waiting period of seven days is required after a whole blood donation before a person can donate platelets. This interval is necessary to allow the blood volume and red cell count to recover.
There is a maximum allowable frequency for platelet donation, typically once every seven days and no more than 24 times within a rolling 12-month period. This restriction is in place to protect the donor from excessive loss of plasma and red blood cells, which are also collected in small amounts during the apheresis process, ensuring long-term donor health.