title: A real-time quantitative polymerase chain reaction method for hepatitis B virus in patients with chronic hepatitis B treated with lamivudine.
abstract: OBJECTIVE
  During treatment of chronic hepatitis B with lamivudine, changes in the level of hepatitis B virus (HBV) DNA were investigated using a real-time polymerase chain reaction (PCR) method with a detection limit of 1.7 log copies/ml (50 copies/ml) to clarify its clinical significance, particularly the association between HBV DNA levels and the emergence of tyrosine-methionine-aspartate-aspartate (YMDD) mutants.
  
  
  METHODS
  Twenty-four patients who had received lamivudine therapy for >1 yr were studied. HBV DNA levels were determined using transcription-mediated amplification for sera with >3.7 log genome equivalents/ml, the Roche Monitor kit for sera with >/=2.6 log copies/ml, and real-time PCR for sera with < 2.6 log copies/ml (the detection limit was 1.7 log copies/ml). Patients were classified into three groups according to the minimal HBV DNA level attained during lamivudine therapy: the <1.7 log copies/ml group (eight patients), the 1.7-2.5 log copies/ml group (five patients), and the >/=2.6 log copies/ml group (11 patients).
  
  
  RESULTS
  Pretreatment HBV DNA levels were significantly lower in the <1.7 copies/ml group than in the other two groups (p < 0.05). Neither the emergence of YMDD mutants nor a virological breakthrough of serum HBV DNA was observed in any of the eight patients in the <1.7 copies/ml group. In contrast, in the 1.7-2.5 copies/ml and >/=2.6 copies/ml groups, virological breakthroughs resulting from the emergence of YMDD mutants were observed in two of five patients and in all 11 patients, respectively (p < 0.001). Virological breakthroughs were observed at a mean of 49.6 +/- 18.4 wk in 11 the patients in the >/=2.6 copies/ml group and at wk 107 and 115 in two patients in the 1.7-2.5 copies/ml group.
  
  
  CONCLUSIONS
  The real-time PCR method is useful for predicting the emergence of YMDD mutants and the estimated time of their emergence.
mesh_terms: D000328:Adult; D001483:Base Sequence; D015331:Cohort Studies; D004252:DNA Mutational Analysis; D004279:DNA, Viral / Q000032:analysis*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D005814:Genes, Viral; D006515:Hepatitis B virus / Q000187:drug effects / Q000235:genetics*; D019694:Hepatitis B, Chronic / Q000188:drug therapy* / Q000235:genetics; D006801:Humans; D019259:Lamivudine / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D011336:Probability; D011379:Prognosis; D011446:Prospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric
chemical_list: D004279:DNA, Viral; D019259:Lamivudine