Use of the Fluorescent Antibody Technique (FAT) for Identifying Weak Subgroups of Red Blood Cells

The technique can be useful in detecting weak subgroups of the ABO blood group system. However, it is not possible to classify these weak subgroups into specific categories, e.g., A3, Am, or Ax, using this technique, since they do not segregate into well defined subgroups but demonstrate a considerable degree of overlap. FAT allows direct observation of the antigens present on red blood cells as opposed to the absorption and elution methods commonly used to identify weak subgroups. Furthermore, saliva studies used for identifying ABO subgroups can be employed in those individuals who secrete soluble blood group substances. Since FAT is not dependent on secretor status, it is valuable for investigating weak subgroups in these persons. (Author)