The routine use of soluble Lewis antigens in the identification of Lewis system antibodies

Approximately 3 percent of the blood samples tested at the authors' laboratory have contained unexpected red cell (RBC) antibodies, of which about one‐third have been anti‐Le(a) or anti‐Le(b). Although these antibodies are usually clinically insignificant, considerable workload was expended in their identification. In hopes of reducing this workload, an alternative approach for identifying these antibodies was implemented. If a patient had no history of unexpected antibodies, with the exception of Lewis system antibodies, and if the results of serum antibody detection testing were typical for the presence of anti‐ Le(a) and/or anti‐Le(b), the serum was treated with commercially standardized soluble human Le(a) and Le(b) blood group substances, and the Lewis phenotype of the patient's red cells was determined. If the treated serum demonstrated specific antibody neutralization and the red cell phenotype was Le(a‐b‐), the results were interpreted as positive for anti‐Le(a) or anti‐Le(b), and no further antibody identification workup was performed. If the patient was Le(a+b‐) or Le(a‐b+), or if the treated serum failed to demonstrate specific antibody neutralization, the serum was tested against panels of reagent RBCs that were licensed for the identification of unexpected antibodies. During the study period (8‐1‐89 to 6‐16‐90), 498 of 46,965 patients' samples met the criteria for testing for specific antibody neutralization. Of these 498 blood samples, 452 showed specific neutralization of antibody activity by Lewis substance and were Le(a‐b‐). Only 1 of these samples was discovered to contain an additional non‐ Lewis antibody (anti‐Bg). The remaining 46 samples either showed specific neutralization but were not Le(a‐ b‐) (n = l), did not show specific antibody neutralization (n = 30), or showed antibody activity that was abolished in a dilution control (indeterminate results, n = 15). The follow‐up on 31 transfused patients whose Lewis antibodies were identified on the basis of specific neutralization of antibody activity demonstrated that the use of the protocol was safe. None of the patients developed a clinically significant non‐Lewis alloantibody or suffered a hemolytic transfusion reaction. A net savings of 10,296 College of American Patholo‐ gists workload units was realized over a 10.5‐month period. This protocol (or one similar to it) might appeal to other facilities that perform antibody detection testing in large patient populations of black or pregnant individuals, in whom a relatively high incidence of Lewis antibodies occurs.