736 Original article Monitoring of therapy in patients with chronic hepatitis B virus Elisabete Arrese a , Miren Basaras a , Sonia Blanco b , Pablo Ruiz b and Ramon Cisterna a,c Objective The aims of this study were to evaluate therapy with lamivudine (LAM) and adefovir dipivoxil (ADV) monotherapy in chronic hepatitis B virus (HBV)-infected patients with frequent measurements of DNA levels, to characterize HBV genotypes, and to determine the emergence of nucleos(t)ide analogue mutants before and during the therapy by direct-sequencing the reverse transcriptase region and by INNO-LiPA HBV DR v3. Materials and methods A total of 15 chronic HBV patients were analysed: 11 were treated with ADV and four were treated with LAM. Results Viral genotype was determined, showing the presence of genotype D (73%) in 11 patients and genotype A (27%) in four patients. In the viral response to treatment, three patients developed substitutions at rtM204I associated with LAM resistance and one of these patients presented rtM204V/I plus rtL180M mutation. In contrast, of the 11 patients treated with ADV, three patients developed mutations (rtN236T; rtA181V; rtA181V plus rtN236T). With regard to this case, the same results were observed by INNO-LiPA HBV DR v3 and direct sequencing, but by direct sequencing we detected an extra mutation rtQ215S that was present in two patients: one patient who was on treatment with LAM had an rtQ215S mutation in addition to an rtM204I, and the second patient treated with ADV had rtA181V. Conclusion Direct sequence analysis is an essential tool to optimize therapeutic management of HBV chronic infection in clinical practice to choose the appropriate nucleos(t)ide analogues and to detect extra mutations that are not included in the commercial kit. Eur J Gastroenterol Hepatol 22:736–740  c 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins. European Journal of Gastroenterology & Hepatology 2010, 22:736–740 Keywords: adefovir, hepatitis B, lamivudine, mutations, resistance, viral load a Department of Immunology, Microbiology and Parasitology, University of the Basque Country, Vitoria-Gasteiz, b Digestive Service and c Department of Microbiology, Basurto Hospital, Bilbao, Spain Correspondence to Elisabete Arrese, PhD, Department of Immunology, Microbiology and Parasitology, Pharmacy Faculty, University of the Basque Country, Unibertsitateko Ibilbidea, 7, 01006 Vitoria-Gasteiz, Spain Tel: + 34 945 01 39 11; fax: + 34 945 01 30 14; e-mail: eli.arrese@ehu.es Received 16 April 2009 Accepted 12 May 2009 Introduction Hepatitis B virus (HBV) infection is a major cause of chronic liver disease. It is estimated that nearly two billion people are infected worldwide by HBV and that more than 350 million have persistent and chronic infection [1]. HBV carriers have a high risk of developing chronic liver disease, cirrhosis and hepatocellular carci- noma [2,3]. The persistence of HBV replication is a clear risk factor for the progression of liver disease and the development of hepatocellular carcinoma [4,5]. There- fore, suppression of viral replication is the most impor- tant goal in the treatment of chronic HBV infection. Nucleos(t)ide analogues suppress HBV replication in most patients and improve transaminase levels and liver histology. Antiviral therapy, available for chronic HBV patients, includes interferon and nucleos(t)ide analogues such as lamivudine (LAM), adefovir dipivoxil (ADV) and en- tecavir. Prolonged treatment with nucleos(t)ide analo- gues can induce mutations in the reverse transcriptase domain of the polymerase gene and confer resistance on antiviral drugs [6,7]. The emergence of drug-resistant mutants is followed by increases in viral load and re- elevation of transaminase levels [8–10]. The success of antiviral therapy has been supported by the introduction of highly sensitive tests for monitoring HBV-DNA. Molecular tests help to determine the activity of HBV infection, the selection of patients for treatment and the efficacy of antiviral therapy, identifying the development of HBV drug-resistant strains [11–13]. According to the molecular analysis of genomic DNA sequencing, HBV strains are classified into eight main genotypes (A–H) [14,15]. There is increasing evidence that the difference in clinical picture, response to treatment and long-term prognosis may be dependent on which genotype has infected the patient [16]. Confirmation of antiviral drug failure can be established by sequencing genetic markers of antiviral drug resistance [17,18]. The aims of this study were to evaluate the therapy in chronic HBV-infected patients with frequent measure- ments of DNA levels, to characterize HBV genotypes and 0954-691X  c 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins DOI: 10.1097/MEG.0b013e32832e0a44