Type and Screen
-Focuses only on your patient’s blood. It doesn’t look at the donor bag of PRBC.
-Typing determines the patient’s blood type.
-Screening screens the patients for the presence of other known antigens on the patient’s RBCs. There is a group of antigens that are known to us and some that we don’t yet know. We screen for the ones we know.
-Type and screen is the first thing you do.
Crossmatching
-Think of crossing or crossbreeding two animals. And think of mixing of bloods.
-Crossmatching takes the patient’s blood that has been typed and screened above (e.g. say AB+) and uses that information to pull out a back of PRBC that is compatible (e.g. it is also labeled AB+). This is not cross matching yet.
-Crossmatching involves mixing a small amount of the patient’s blood and a small amount of blood taken out of the donor blood. Crossmatching really is physically mixing two people’s bloods (that you have screened and think should be compatible) in a container to see if agglutination happens. If agglutination happens, it tells you that there are some unknown antigens on the patient’s RBCs that are reacting badly with the donor’s blood. As such, even though the type and screen was done, you won’t transfuse because the crossmatching failed. Actually mixing blood in a container is called Manual Crossmatching.
Electronic crossmatching allows the known identified antigens on the two bloods (from typing and screening) to be matched electronically without actually mixing the bloods. It’s not as foolproof as manual crossmatching. Manual crossmatching has to be used in people who have a history of previous transfusions and
Manual crossmatching has to be done when 1) the patient screened positive for some antigen or 2) if the patient has a history of previous transfusions. Otherwise, if both patient and donor blood have matching types, screen negative, and the computer says they should be able to match, electronic crossmatching is considered sufficient and we simply trust that there are no hidden antigens that would cause a reaction when the patient is actually transfused.