External control is an important part for ensuring quality of immunohaematological examinations on which depends the safety of transfusion substitution treatment. In the Czech Republic external control was introduced in 1992. During the first two years control was ensured entirely by the Reference laboratory for immunohaematology at the Institute of Haematology and Blood Transfusion (ÚHKT), in subsequent years in the organizational and administrative part SEKK participated. Within the framework of external control the following examinations are followed up: assessment of AB0, assessment of RhD, assessment of other erythrocyte antigens, direct antiglobulin test, antibody screening and antibody identification. The number of participating laboratories increased from the initial 38 to more than 200. The results are evaluated according to different parameters and presented in figures and tables. In the basic examinations, AB0 and RhD assessment, there are long-term satisfactory results in normally expressed antigens, problems arise only in weak and variant antigens. In another basic examination, screening of alloantibodies, an improving trend is observed. Difficulties persist as regards detection of weaker antibodies which react only in the indirect antiglobulin test, in particular when the classical tube test technique is used.

        Key words: external control, assessment of AB0 RhD, assessment of other red cell antigens, direct antiglobulin test, antibody screening, alloantibody identification