Table 2.

Platelet ABO compatibility

ABO		Platelet recipient ABO group
		AB	A	B	O
Platelet donor ABO group	AB	Identical	Major	Major	Major
	A	Minor	Identical	Bidirectional	Major
	B	Minor	Bidirectional	Identical	Major
	O	Minor	Minor	Minor	Identical

RhD		Platelet recipient RhD type
		Positive		Negative
Platelet donor RhD type	Positive	Identical		Mismatch
				At risk for RhD alloimmunization
	Negative	Mismatch		Identical
		No risk for RhD alloimmunization

ABO identical: donor and recipient have the same ABO antigens and antibodies. Major ABO mismatch: donor ABO antigens are incompatible with recipient ABO antibodies. Minor ABO mismatch: donor ABO antibodies are incompatible with recipient's ABO antigens. ABO bidirectional mismatch: donor ABO antibodies are incompatible with recipient ABO antigens and donor ABO antigens are incompatible with recipient ABO antibodies. Rh mismatch: Rh type of the recipient is different from the Rh type of the donor. RhD-negative recipients of platelets obtained from RhD-positive donors are the only ones at risk for RhD alloimmunization.