For Transfusion Services - I think if you are getting extraneous or nonspecific reactions you should increase your rule outs to at least 2 homozygous (with exceptions, of course), but for the majority of workups I think one homozygous is perfect, especially with the sensitive methods most of us are using today. Also, IMO, ruling out on heterzygous cells is a waste of time and dangerous for some antibodies that show dosage. R1R2