When I first look at my antibody screen and ID panel, the first thing I do is go to my negative reactions and cross off cells that are single dose "homozygous" for the antigen group. Next, I look at the double-dose "heterozygous" cells and, if I have 3 or more, I will cross those out as possiblities. Normally, I have a clear cut answer at this point, which is then evaluated to make sure I have 3 positive cells that reacted and 3 negative that did not. If there is more than one possibility, I do "rule-out" panels to either prove the existence of the addtional antibody or rule it out. I believe Mabel Adams had an excellent power-point that perfectly illustrated this approach. It has been very helpful. Of course, there are often "stray" reactions or cells you would expect to react that don't. You just have to use technical skills and techniques to investigate these reaction to a conclusion that your pathologist will accept.