The System

• Antigens on red cells set your type
• ABO system marks antigens A and B
• Rh system adds the D antigen
• Plasma antibodies reject the wrong markers

Universal Donor

• O-negative gives to all recipients
• Carries neither A, B, nor D
• Default when type is unknown
• Reserve it for true emergencies

Universal Recipient

• AB-positive receives all eight types
• Carries A, B, and D antigens
• Holds no rejecting antibodies
• Note this applies to packed cells

Compatibility Rules

• Match recipient and donor antigens
• Apply chart to packed cells only
• Hold whole blood to stricter rules
• Honor cross-matching every time

Global Prevalence

• O-positive is the most common type
• A-positive follows close behind
• Negative types stay relatively rare
• AB-negative is the scarcest

Regional Intel

• Expect distribution to vary by region
• Use local data when available
• Don't assume global averages hold
• Plan supply around the population

Field Considerations

• Confirm type before any transfusion
• Treat cross-matching as non-negotiable
• Account for prior transfusion history
• Default to O-negative under doubt