Unexpected limitations in the use of commercial antiglobulin reagents.
The majority of antiglobulin sera used in blood banks in the USA are commercially prepared immune rabbit sera, designed to be reactive only with human red blood cells sensitized with immunoglobulins or complement components. Current manufacturing methods result in a product that gives reliable specific reactions provided that the test red blood cells are normal, particularly with respect to sialic acid levels. This report describes our findings of false positive antiglobulin tests caused by incompletely absorbed antiglobulin reagents when cells with low sialic acid levels were tested. An evaluation of nine commercially prepared antiglobulin reagents revealed, in many of them, the presence of anti-species antibody, anti-T, and anti-Tn. Blood bank personnel must be aware of these characteristics especially when testing either enzyme premodified or polyagglutinable cells. The use of incompletely absorbed reagents might account for positive direct antiglobulin tests that are encountered occasionally in apparently normal healthy individuals. Furthermore, recent protocols advocating the use of trypsinized cells for the evaluation of anti-C3d activity of antiglobulin sera are invalid if the reagent is inadequately absorbed of anti-species agglutinins.
D000373:Agglutinins; D000888:Antibodies, Anti-Idiotypic / Q000592:standards*; D001771:Blood Banks; D001789:Blood Group Antigens; D003120:Colorado; D003298:Coombs Test; D004912:Erythrocytes / Q000032:analysis / Q000276:immunology; D005189:False Positive Reactions; D006801:Humans; D012794:Sialic Acids / Q000097:blood; D013045:Species Specificity
D000373:Agglutinins; D000888:Antibodies, Anti-Idiotypic; D001789:Blood Group Antigens; D012794:Sialic Acids