RESUMEN
BACKGROUND: Rouleaux agglutination is a common cause of difficult blood typing, but it is rarely reported in patients with acute brain trauma. METHODS: This article describes a 69-year-old male with head injury who was admitted to the hospital. Blood typing showed type O, Rh(D) positive, but the Rh(D) control was also positive. After ruling out the possibility of the patient having abnormal autoantibodies, it was suspected that rouleaux agglutination might be the cause. Microscopic examination of the specimen revealed rouleaux agglutination, which was believed to be the cause of the false-positive Rh(D) control result. The patient's red blood cells were treated with physiological saline and retested by microcolumn gel card testing. RESULTS: The retest showed negative Rh(D) control results, indicating normal results. The patient subsequently received normal blood transfusion. CONCLUSIONS: Laboratory personnel should be aware of the possibility of difficult blood typing caused by rouleaux agglutination in various diseases, especially in relatively rare traumatic diseases.