False-positive results with third-generation monoclonal hepatitis B surface antigen enzyme immunoassay

Nonspecific hepatitis B surface antigen reactions with a third-generation enzyme immunoassay (Auszyme Monoclonal; Abbott Laboratories, North Chicago, Ill.) were investigated with 9,577 serum specimens in a clinical laboratory setting. Of the 196 serum specimens found reactive in Auszyme screen by the overnight procedure, 103 turned out to be true-positives, 71 were nonrepeatably reactive, and 22 were repeatably reactive but actually falsely positive (false-positive rate, 22 of 196, or 11.2%). Verification of the 196 screen reactives by the Auszyme 3-h incubation assay detected all but 4 true-positives, with a false-negative rate of 3.9% (4 of 103), and was negative for the rest. These observations reinforce the need for retesting all reactive specimens and confirming repeatedly reactive samples when the Auszyme Monoclonal test is used to detect hepatitis B surface antigen.