Lamivudine is an effective antiviral agent in the treatment of patients chronically infected with hepatitis B virus. It competitively inhibits viral reverse transcriptase and terminates proviral DNA chain extension, which leads to a marked decrease in HBV DNA levels, usually followed by improvements in alanine aminotransferase levels and liver histology. However, HBV strains with mutations in the conserved YMDD motif of the HBV polymerase gene emerge in an increasing proportion of patients after long-term mono-therapy with lamivudine.
Patients with resistance mutants characteristically develop HBV DNA breakthrough and rise in ALT. Addition of Adefovir dipivoxil (ADV) to the treatment regime is current practice.
In the majority of lamivudine-resistant isolates the mutations have been reported to occur within the YMDD motif of the viral polymerase, either as a single mutation M204I or as M204V concomitant with L180M.
Adefovir resistant virus has been reported and already detected in New Zealand. The mutations conferring ADV resistance are also found within the polymerase gene fragment amplified by the current assay. Specific mutations associated with ADV resistance are: A181T/V, Q215S and N236T.
This assay is designed to detect polymerase resistance by amplifying a 492 base pair fragment of the polymerase gene, which is then sequenced and analysed for drug resistance associated mutations.
Source: LabPlus Test Guide
Microbiology - Virology
YMDD
Test can be added to a HBV VL request if the viral load result is greater than 1,000 IU/mL. Testing performed by LabPlus, Auckland.
Lamivudine resistance
Lamivudine YMDD Mutation
M204I or M204V Mutation
Hepatitis B resistance genotyping
HBV drug resistance
4 weeks
7854