Abstract: Objective To analyze the cause of acute immune hemolytic transfusion reaction in a patient during blood transfusion, and explore the clinical detection methods and coping strategies of easily attenuated and low titer blood type antibodies in immune hemolytic transfusion reaction. Methods ABO, Rh, Kidd blood type test, unexpected antibody identification in serum and red blood cell eluate, direct anti-globulin test were performed on patients. Combined with the patient's clinical symptoms and laboratory test results, the types of unexpected antibodies that caused hemolytic transfusion reactions in the patient's body were detected. Results The patient's blood type was A type, CCDee, Jk(a-b+), Anti-E antibodies were detected in the serum. After the fifth transfusion, the patient experienced an acute hemolytic transfusion reaction. The PEG enhanced method was used to detect the presence of new anti Jk^a antibodies in the sample before the transfusion reaction, and the red blood cells of the donor were CCDee, Jk(a+b+), the PEG method and CCDee, Jk(a+b-) homozygous donor red blood cells were cross matched with the pre transfusion specimen of the patient, and both sides were mismatched, resulting in hemolytic transfusion reactions in the patient. Conclusion Kidd blood type system antibodies often rapidly decrease and have low potency both in vitro and in vivo. Conventional laboratory testing methods are prone to missed detection, and this antibody has a dose effect, leading to the omission of heterozygous red blood cells incompatible in cross matching, resulting in acute hemolytic transfusion reactions. It is recommended that the laboratory be alert to the production of Kidd blood type system antibodies in the serum of patients who have undergone multiple blood transfusions. A comprehensive testing method should be built up to improve the sensitivity of antibody detection. At the same time, for the same type of antibodies that have been produced, they should be recorded and archived, and the patient and clinical physician should be informed in advance to the transfusion department before the next blood transfusion to avoid serious hemolytic transfusion reactions in patients.

Key words: Kidd blood type, Acute hemolytic transfusion reaction, Unexpected antibodies