The Rh blood group is identified by the presence or absence of the D antigen on the red blood cell membrane in the blood. The presence of D antigen on the red blood cell membrane is recognized as Rh-positive blood, while the absence of D antigen is recognized as Rh-negative blood. The clinical method of testing Rh blood type is as follows: take a small amount of the examinee’s blood and place it on a slide, then drop the serum containing anti-D antibody into the examinee’s blood, and if agglutination occurs (i.e., the formation of blood clots), then it will be Rh-positive blood, which will be indicated by Rh (+). Conversely, if no agglutination occurs, the blood is Rh-negative, indicated by Rh (-). The vast majority of Chinese are Rh-positive, with only 0.3% of Han Chinese being negative. However, there is no difference in physiological function between Rh-positive and Rh-negative blood.