Table II.

Top-20 alloantibodies and corresponding antigen(s)-negative frequencies

Antibody (anti-)	Cases	Proportion	Antigen-typed cases	Antigen-typed units	Obtained units	Antigen(s)-egative frequency	Units required for typing*
E	2,202	27.6%	1,305	4,194	3,027	72.2%**	2
E, c	1,792	22.5%	1,343	4,251	2,957	69.6%**	2
C, e	757	9.5%	555	1,880	1,091	58.0%**	2
Le a	618	7.7%	110	451	313	69.4%	2
M	383	4.8%	197	1,902	415	21.8%	5
Jk a	323	4.0%	215	1,741	491	28.2%	4
Fy b	283	3.5%	228	1,001	743	74.2%	2
Le b	278	3.5%	62	319	163	51.1%	2
P1	202	2.5%	137	731	421	57.6%	2
Di a	116	1.5%	37	135	98	72.6%	2
c	113	1.4%	99	425	283	66.6%**	2
Jk b	94	1.2%	67	811	185	22.8%	5
S	87	1.1%	61	272	180	66.2%	2
C	67	0.8%	29	94	46	48.9%**	3
Le a , Le b	62	0.8%	17	132	46	34.9%	3
e	59	0.7%	36	82	64	78.1%**	2
E, Fy b	42	0.5%	25	108	83	76.9%**	2
C, e, Jk a	37	0.5%	11	450	28	6.2%**	17
E, c, Jk a	33	0.4%	22	162	68	42.0%**	3
E, Jk a	32	0.4%	26	191	54	28.3%**	4

^*Mean number of units needed to be typed in order to find one compatible unit.

^**Antigen(s)-negative frequencies including C, E, c, and/or e were overestimated because many blood banks preselected C-, E-, c-, and/or e-negative units through the Blood Information Sharing System (BISS) and performed retyping (see Table III).