D Antigen

Abstract

Background: In 1939 Rh antigen was discovered by Levine and Stetson. Rhsystem antigens are very immunogenic, they can produce significant Hemolytic Disease of thefetus and Newborn as well as hemolytic transfusion reactions. There are numerous variants ofD, the most common subtypes are Weak D and Partial D, now called as abnormal D antigens.The incidence of Rh negativity worldwide varies between 3%-25% and that of weak D antigenranges from 0.2%-1%. Objectives: To find out the frequency of Rh negativity and weak Dantigen among the donors coming to the blood bank of The Children’s Hospital & Institute ofChild Health, Lahore and to review the clinical significance of weak D antigen in transfusionperspective especially its role in alloimmunization caused by Weak D antigen when transfusedto Rh negative individuals. Study Design: Cross- sectional study. Setting: The Children’sHospital and Institute of Child Health, Lahore. Period: 1st Jan 2015 to 31st May, 2015. Materialsand Methods: 6320 healthy donors were randomly selected. All samples were grouped forABO and Rh-D factor by immediate spin tube technique. All samples found Rh negative, werefurther processed for weak D antigen with monoclonal anti D sera by using indirect Coomb’stechnique. The presence of macroscopic or microscopic agglutination was recorded as Rhpositive. In case there was no agglutination the mixture was washed 4 times with normalsaline. After the last wash, saline was decanted and 2 drops of monoclonal, polyvalent antihuman globulin was added. Macroscopic and microscopic agglutination was looked for andany agglutination at this stage was recorded as weak D antigen. Positive control (check cellsi.e. washed O positive cells with diluted anti D) and negative control (washed O positive cells)were always put. Results: Among the 6320 healthy donors, 1224(19.4%) were Rh-D negativeand 5096(80.6%) were Rh-D positive. Of the 1224 Rh D negative samples, 3 (0.2%) samplesfound positive for weak D antigen. Conclusion: The frequency of Rh negative blood groupwas 0.2% among the healthy donors at The Children’s Hospital and ICH, Lahore. Although thefrequency is low but it’s proven by literature that weak D antigen can produce alloimmunizationif transfused to Rh-D negative subjects. At the same time the cases of hemolytic reactionsreported previously with Weak D antigen have been scarce.