The type and screen determines both the ABO-Rh of the patient and screens for the presence of the most commonly found unexpected antibodies.
ABO-RH testing (the “Type”): The patient’s blood cells are mixed with serum known to have antibodies against A and against B to determine blood type. The patient’s blood cells are also treated with anti-D antibodies to determine Rh.
Antibody Screen (the “Screen”): The purpose of this test (also known as the indirect Coombs test) is to detect the presence of the most common antibodies in the patient’s serum. Essentially, the patient’s serum is mixed with red cells of known antigenic composition.
Hemolytic Reactions and Justification for Crossmatching
The incidence of a serious hemolytic reaction after transfusion of an ABO-Rh compatible transfusion with a negative screen is less than 1%. Crossmatching (NOT part of a type and screen) where actual donor cells are mixed with the recipient’s serum reduces the risk of a serious hemolytic reaction to essentially zero.