Abstract: Objective To approach the reasons and characteristics of question blood group among blood donors in the area,provide basis for accurate typing of blood and clinical blood transfusion safety. Methods The blood group examination of RBC blood group was proceed in healthy donors in our center from January 2008 to December 2015. All the unconformity of positive and passive defined ones and the agglutination of negative O cell for comparison were defined as question blood group. The question blood groups were sent to blood typing reference center for further identification. Its causes and characteristics were analyzed. Results Among 285 282 blood samples,375 cases of question blood groups were screened out with the positive rate of 0.139%. 168 cases were men with the positive rate of 0.110%; 228 cases were women with the rate of 0.172%. The positive rate of women was higher than that of men with a statistical significance. For the causes of question blood group,316 cases of specific antibody were detected,accounting for 79.8%,28 cases were cold agglutinin,account for 7.1%,21 cases were nonspecific antibody,accounting for 5.3%. Anti-M（24.4%）,cold antibody （21.9%）and ABO isoforms（19.3%） were common specific antibody of causing the question blood group. The AχB（27.9%） and A₂B （13.1%） isoforms of AB typing of blood and B3 isoforms（11.5%） of B typing of blood were common types of ABO isoforms of causing the question blood group. Conclusion Certain detection rate of question blood group exists among blood donors. Many reasons could cause the occurrence of question blood group. Accurate blood group examination and reason analyses of question blood group could provide an important basis for the safety of clinical blood transfusion.

Key words: Blood group examination, Question blood group, Anomalous antibody, ABO isoforms, Safety of blood transfusion