Hepatitis B surface antibody testing was only done on hepatitis B core antibody positives. In 1993, 495 additional samples from participants with a medical occupation who were negative for antibody to hepatitis core antigen were tested to determine mIU/ml of antibody to assess vaccination status. Results of the serum hepatitis B surface antibody can not be used to estimate the vaccination status of the U.S. population since all participants were not tested for this serologic marker.
Additional note to explain possible storage effect on analytes in biochemistry profile
Sera for the Biochemistry Profile was stored at –20° C and then thawed at room temperature. This freeze/thaw cycle has been demonstrated to result in degradation for some analytes in this profile (1-2). Analytes should therefore be used cautiously since degradation could have occurred.