Division of Gastroenterology and Hepatology, Department of Medicine, Queen Mary Hospital, The University of Hong Kong

The end-points for the assessment of the efficacy of anti-viral therapy are usually focused on the reduction of HBV DNA, hepatitis B e antigen seroconversion, the normalization of transaminases and improvement of the liver histology. Viral load, as reflected by the HBV DNA level, is often taken as the most sensitive and reliable marker for monitoring therapeutic efficacy. At present, the assays used for the measurement of HBV DNA in clinical trials vary considerably with highly different sensitivities. In-house HBV DNA assays are notoriously variable in standardization and sensitivity. Different commercially available methods of HBV DNA assays commonly used in clinical trials will be discussed. They include radiological molecular hybridization assay, quantiplex HBV DNA assay, Digene hybrid capture assay, NAXCOR crosslinking nucleotide assay and amplicor HBV monitor test. One major problem with the commercially available assays of serum HBV DNA measured in the different assays may vary by a factor of up to 120. Reference plasma samples have already been used in the standardization of test kits. Unless, the standard is strictly adhered, the problem of divergent results in different laboratories will remain.