As part of the monitoring of hepatitis B screening activities by the Rena-VHC/B laboratory network, the marker selected was the HBs antigen (HBsAg).

Case definition

Inclusion in the surveillance of any patient serum collected at a participating laboratory for a screening test or a follow-up test that was positive for the HBs antigen (HBsAg).

Excluding serum samples from children under one year of age and serum samples from other laboratories.

Other definitions

Tests

• Screening test or serology: detection of HBs antigen (ELISA technique) in a blood sample from a person presenting at the laboratory for the first time.

• Confirmatory test: detection of HBs antigen by neutralization or a confirmatory ELISA test in the event of a positive or equivocal screening test in a patient not previously known to the laboratory as HBsAg-positive. The test used to perform this confirmatory test is determined by the participating clinician.

Indicators

• Overall serological activity: total number of HBsAg serological tests (ELISA, neutralization) regardless of indication (screening, confirmation, and unspecified indication) performed over a given period.

• Overall positivity indicator: ratio of the number of positive HBsAg tests (screening, confirmatory, and unspecified indication) to overall serological activity.

• Positivity control indicator: ratio of the number of positive control/confirmation tests to overall serological activity.

• Person diagnosed as HBsAg-positive: a person for whom both the screening test and the confirmatory test are positive.