Quantitative measurement of HBeAg in chronic hepatitis B: a comparison between a radioimmunoassay, a fluorescence ELISA and a chemiluminescence ELISA.

The presence of the hepatitis B e antigen (HBeAg) in peripheral blood of chronic hepatitis B patients is a widely accepted marker of active replication of the hepatitis B virus. HBeAg determination during interferon therapy is a useful guide for the therapeutic regimen. The aim of the study was to compare the suitability of an HBeAg radioimmunoassay (RIA, Abbott Laboratories, North Chicago, IL, USA), the IMx-HBeAg assay (IMx, Abbott Laboratories) and the HBeAg/anti-HBe Amerlite assay (Amerlite, Johnson & Johnson Clinical Diagnostics, Cardiff, UK) for semiquantitative monitoring of HBeAg during therapy. HBeAg levels in serum samples obtained before and during interferon therapy were measured using an in-house standard calibrated against the Paul Ehrlich Institute HBeAg reference preparation (PEI standard). When serial dilutions of pretreatment serum samples were assayed by the three methods, radioimmunoassay was found to be highly sensitive although it had a very limited working range (0.5 to 12 PEI U/ml). A broader linear working range was observed for Amerlite (0.5 to 50 PEI U/ml) and the IMx assay (0.5 to 100 PEI U/ml). The intra-assay and interassay variations did not differ significantly. Since the IMx assay was less susceptible to sample variation and had a broad working range, semiquantitative measurement of HBeAg in one diluted and one undiluted sample by this assay may justifiably be introduced as routine procedure. Routine semiquantitative HBeAg measurement may improve individual dose adjustments and thus the success of interferon therapy.