[Problem-solving in immunohematology: direct compatibility laboratory test ].

Cross-matching between the serum of a patient and the red blood cells to be transfused is most important for the prevention of hemolytic transfusion reactions in allo-immunized or new-born patients found positive with direct antiglobulin test. Cross-matching is a time-consuming and complex laboratory test. In order to obtain valid results, it is necessary to abide by some technical rules detailed in this article. The choice of the blood units to be cross-matched depends on the patient's clinical story and on the specificity of anti-erythrocyte antibodies present in the serum. The identification and the management of most frequent difficulties met by using the cross-match technique are discussed hereby.