Dear Editor,A common reason for drug failure during long-term treatment of chronic hepatitis B with nucleot(s)ide analogues(NUCs)is the emergence of drug resistance(Das et al.,2001).Most primary NUCs-resistant mutations identified in clinical samples have been limited to a minority of amino acids(usually less than Dear Editor, A common reason for drug failure during long-term treatment of chronic hepatitis B with nucleot (ide) analogues (NUCs) is the emergence of drug resistance (Das et al., 2001). Primary primary NUCs-specifically identified in clinical samples have been limited to a minority of amino acids (usually less than