Hepatitis B virus - YMDD Mutation Detection

Test Identifier Information

Sequence analysis.

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.

Current resistance assay looks for mutations to the following 5 drugs:

Lamivudine, Adefovir, Entecavir, Telbivudine, Tenofovir

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.

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.

Specimen Collection

Centrifuge EDTA(Lavender) whole blood at 800-1600xg (rcf) or 3500rpm for 20 minutes at room temperature within 4 hours of collection.

In a biohazard cabinet: Transfer plasma aseptically using sterile pipettes provided into a yellow topped Serology tube supplied by CHLabs. Half fill two tubes. Wear gloves at all times.

Instructions for Referral to CHLabs

CHLabs Laboratory

Results are reported showing Antiviral drugs and level of resistance and mutation.

R{High level risistance} S{Susceptible} I{Intermediate level resistance}

Full clinical details are essential.

The antiviral therapy adefovir is now funded by Pharmac (May 2006), and will be available to patients that have resistance to lamivudine. Long term use of lamivudine may be associated with HBV YMDD mutation.

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.

The current resistance assay looks for mutations to the following 5 drugs:Lamivudine, Adefovir, Entecavir, Telbivudine, Tenofovir