Evaluation of a line probe assay for identification of hepatitis B virus precore variants in serum from chronic hepatitis B carriers

A prototype line probe assay (LiPA) for identifying hepatitis B virus (HBV) precore variants (INNO-LiPA HBV precore) was evaluated using a panel of 50 sera from 46 patients with HBV infection. The assay detected sequence variations detected commonly in the precore promoter region and in amino acid codons 28 and 29 of the precore gene. There was strong agreement between INNO-LiPA HBV precore results and those of a codon 28 point mutation assay (PMA), with identical results obtained in 40 of 43 sera (93%) typeable by both assays (kappa coefficient (kappa)=0.90). In addition, the precore codon 29 sequence identified by the INNO-LiPA HBV precore was confirmed by nucleotide sequencing in all seven samples analysed. However, the INNO-LiPA HBV precore identified precore promoter sequences much less efficiently. The prototype assay could identify codon 28/29 sequences from as little as 10 HBV genome equivalents in 10 microl serum, and in experiments using artificially prepared mixtures of variants could identify a minor component constituting 2.5% of the total viral DNA population. The INNO-LiPA HBV precore was also straightforward technically and rapid, and is therefore likely to be useful for epidemiological investigations into the prevalence, distribution and clinical significance of HBV precore variants.