Sensitivity of passive bacterial agglutination for detection of hepatitis B surface antigen

The sensitivity of passive bacterial agglutination (PBA), i.e., the agglutination of Staphylococcus aureus coated with antibodies to hepatitis B surface antigen by hepatitis B surface antigen, was assessed by testing reference panel no. 3A sera (Bureau of Biologics, U.S. Food and Drug Administration). Of the 23 samples containing hepatitis B surface antigen, 18 were positive by PBA. Sera from 100 healthy adults were tested by PBA and reversed passive hemagglutination. Four sera were positive by both methods. One additional sample was positive only by PBA; if one assumes that it was a false-positive result, the rate of false-positive reactions was only 1%.