Lamivudine resistance of hepatitis B virus masked by coemergence of mutations in probe region of the COBAS AMPLICOR assay.

The COBAS AMPLICOR hepatitis B virus assay targets a conserved region of the genome and is widely used to monitor treatment of hepatitis B in order to identify emerging resistance. However, the assay failed to recognize increasing viremia levels when YMDD mutations were paralleled by mutations in the segment targeted by the COBAS AMPLICOR probe.