Measurement of HBsAg to monitor hepatitis B viral replication in patients on alpha-interferon therapy.

HBsAg was measured quantitatively in serum samples collected serially before and after the HBeAg seroconversion date from 69 patients with HBeAg seroconversion and 17 patients with both HBeAg and HBsAg seroconversion. In patients with only HBeAg seroconversion the median HBsAg level decreased from 8.39 micrograms/ml (range 0.01-57.51) before HBeAg seroconversion to 3.53 micrograms/ml (range 0.002-68.66) after seroconversion (P < 0.001). No significant drop in HBsAg was found for the control group (18 HBeAg-positive patients without seroconversion). From 12 other patients on alpha-interferon therapy HBsAg was quantitatively assayed monthly during and after therapy; HBsAg levels were compared to the levels of HBV-DNA and HBeAg. We observed a good correlation between the HBsAg level and both the HBV-DNA (r = 0.76; P < 0.001) and the HBeAg (r = 0.70; P < 0.001) level, irrespective of the response to alpha-interferon. Quantified assessment of HBsAg appears promising as a simple and cheap method for monitoring viral replication in chronic hepatitis B in patients undergoing interferon therapy.