Whole Blood and Blood Components: Donor Eligibility, Collection, Processing, Storage, and Indications
Core concepts
Whole blood is collected into an anticoagulant-preservative solution; the choice of solution determines storage length and the component yields. CPD/CP2D allow 21 days; CPDA-1 allows 35 days; additive solutions (AS-1, AS-3, AS-5) extend red cells to 42 days. Know that whole blood is rarely transfused as such-it is the source for red cells, platelets (from platelet-rich plasma or buffy coat), plasma, and cryoprecipitate.
Donor eligibility rests on FDA regulations and AABB Standards: minimum hemoglobin/hematocrit (12.5 g/dL or 38% for females, 13.0 g/dL or 39% for males), minimum weight 50 kg, 8-week interval between whole blood donations, and a 56-day interval for double red cell donation. Deferral periods are high-yield: permanent for viral hepatitis after age 11, HIV risk, and certain malignancies; 3 months for pregnancy, 12 months for tattoos/piercings in some jurisdictions, and travel-related malaria deferrals.
Traps
Questions love the distinction between storage lesion effects (2,3-DPG depletion, potassium leak, pH fall) and true shelf-life limits. Red cells stored in additive solution are held at 1–6°C; platelets at 20–24°C with agitation for 5 days (7 with approved systems); plasma frozen at ≤−18°C for 12 months (24 months if frozen within 24 h of collection). Leukoreduction to <5×10^6 WBCs reduces febrile reactions and CMV transmission.
Rule of thumb
When a stem asks "which component," match the deficiency: factor VIII/fibrinogen → cryoprecipitate; volume plus oxygen carrying → whole blood or red cells; isolated coagulopathy → plasma. Always check the interval and storage temperature before the indication.