[A new hemagglutination method to determine antibodies against Entamoeba histolytica].

A passive hemagglutination method useful for the determination of antibodies against Entamoeba histolytica is described. The E. histolytica antigen is attached to group "O" human red blood cells by means of CrCl3. The specificity and sensitivity of the CrCl3 method was compared with other hemagglutination methods, i.e., tannic acid method and a commercial preparation, as well as counterimmunoelectrophoresis. The CrCl3 method showed a reactivity similar to the tannic acid hemagglutination technique and greater specificity than the commercial preparation. The assay reported here showed a good correlation with the counterimmunoelectrophoresis method. The sensitization of erythrocytes with the amebic antigen by means of CrCl3 offers an easy, rapid and specific technique which can be used as a routine test for the detection of antibodies against E. histolytica.