We call it group checking, and we use instant spin tube technique. We test O units with anti-A,B, and all the other types with anti-A and anti-B, and additonally all Rh(D) negative units with anti-D. Weak D testing is not considered necessary. We didn't do any of that until we started electronic issuing, though, before that we did an instant spin crossmatch before all issues, and that was considered sufficient.