A sensitive and accurate HBV
DNA quantification assay is essential for monitoring hepatitis B virus (HBV) replication. This study evaluated a real-time PCR method performed in the LightCycler analyser for quantitative HBV
DNA assay. HBV
DNA results with this method were compared with those obtained using a branched-chain
DNA (bDNA)
solution hybridization assay. Real-time PCR was performed using two adjacent fluorescently labelled probes and primers corresponding to the HBV core gene. The same standard employed in the bDNA assay was used for calibration. Serum samples came from 193 HBV
surface antigen (
HBsAg)-positive patients (34 HBV
e antigen (
HBeAg)-positive and 93 with antibody to
HBeAg (anti-HBe)), and 66 asymptomatic HBV carriers. In addition, we analysed serum samples from 8 anti-HBe-positive patients who had been receiving
lamivudine treatment for more than three years. A linear standard curve was seen in the range from 10(3) to 10(8) copies/mL. In the reproducibility analysis, intra-assay coefficient of variation (CVs) at two known HBV
DNA concentrations were 4% and 2% and interassay CVs were 6% and 4%. The median of serum HBV
DNA by real-time PCR was 9.2 x 10(8) copies/mL in
HBeAg-positive patients with persistently elevated
alanine aminotransferase (ALT) levels, 1.3 x 10(7) copies/mL in anti-HBe-positive cases with persistently elevated ALT levels, 3.7 x 10(4) copies/mL in anti-HBe-positive patients with fluctuating ALT levels and 10(4) copies/mL in asymptomatic HBV carriers. The differences in HBV
DNA levels among the various groups studied were statistically significant (P < 0.05). The cut-off between
chronic hepatitis patients and asymptomatic carriers was found to be at a serum HBV
DNA concentration of 5 x 10(4) copies/mL. Of the 109 serum samples with a viral load < 7.5 x 10(5) (negative by bDNA assay) 44 (40%) were positive by real-time PCR: 24 (56%)
chronic hepatitis and 20 (33%) asymptomatic carriers. There was a positive association between HBV
DNA levels determined by real-time PCR and ALT levels (P < 0.05), which was not observed with the bDNA assay for HBV
DNA quantification. At 12 months of
lamivudine treatment, 6 patients (75%) showed HBV
DNA levels < 5 x 10(4) copies/mL (range < 10(3)-2 x 10(3)), significantly lower than at baseline. At 36 months, 2 of 8 (25%) showed HBV
DNA levels persistently lower than 5 x 10(4) copies/mL (1.7 x 10(3), 6 x 10(3)). The LightCycler quantitative real-time PCR is a practical, sensitive, reproducible single-tube assay with a wide dynamic range of detection. The assay is automatic except for
DNA extraction and the running time is only 70 min. The LightCycler real-time PCR is useful for identifying different states of HBV
infection and for evaluating the efficacy of viral
therapy.