[External Quality Control in Immunohematology of National Medical Center's Blood Bank. History and present].

For the proper functioning of the Immunohematology Area, an External Quality Control was established since 1973 through a program that evaluates the performance of the laboratories of the Blood Bank and transfusion services that carry out immunohematology tests. This program consists of sending panel cells to participating blood banks or services, which are phenotyped erythrocyte samples previously studied as problem cases but whose results are unknown by the participating laboratories. The processes in which the program is of most importance are determination of the ABO group, determination of Rh, performance of the direct and indirect Coombs test, and pre-transfusion compatibility tests.