We compared the sensitivity of the polymerase chain-reaction (PCR) assay to that of slot-blot hybridization for detecting hepatitis B virus (HBV) DNA in the serum of 31 patients with chronic hepatitis. Of 14 chronic hepatitis patients positive for both HBV surface and HBV e antigens, 9 were positive for HBV DNA by slot-blot hybridization and all 14 by PCR. Also, of 9 patients positive for HBV surface antigen and antibody against HBV e antigen, 2 were positive for HBV DNA by slot-blot analysis and 8 by PCR. Finally, in 8 patients positive for antibody against HBV surface antigen, none were positive for HBV DNA by slot-blot hybridization, but 4 were positive by PCR. We find that analysis by the PCR technique provides a >104-fold increase in sensitivity over the slot-blot hybridization assay. This result represents an important breakthrough in sensitivity because it is now possible to detect as few as three HBV DNA genomes per sample of serum.The polymerase chain reaction (PCR) technique is a method for amplifying nucleic acid by repeated cycles of hightemperature template denaturation, oligonucleotide primer hybridization, and polymerase extension. The thermostable polymerase of Thermus aquaticus (Taq) is often used because it can withstand the high denaturation temperatures without loss of enzymatic activity. Previous investigations with this technique have shown amplification of >105-fold over the input quantity of nucleic acid (1, 2). We have used PCR amplification, combined with agarose gel electrophoresis and Southern blot hybridization analysis, to detect extremely small quantities of hepatitis B virus (HBV) DNA in the serum of chronic hepatitis patients.

Group I and II hepatitis C virus genotypes were determined by a newly developed serological genotyping assay. This assay detected antibodies against group-specific recombinant proteins in the putative NS4 protein region (amino acid no. 1676-1760) by an enzyme-linked immunosorbent assay. This region of the hepatitis C virus peptide has many group-specific amino acids; fewer than 50% of these amino acids are identical between groups I and II. Genotypes determined by the serological genotyping assay were compared with those determined by a method in which the polymerase chain reaction was used in 91 chronic hepatitis patients. The group-specific polymerase chain reaction was performed within the genome region corresponding to the putative NS5 protein, where the group II hepatitis C virus genome is 57 nucleotides longer than that of group I. Among 91 chronic hepatitis C patients who had positive results in the second-generation hepatitis C virus antibody (core and NS3 region) assay, hepatitis C virus RNA was detected in 80 patients by polymerase chain reaction in the 5' untranslated region and in 78 patients by this group-specific polymerase chain reaction. As a result, in 76 of 91 patients (84%) genotypes determined by the serological genotyping assay showed complete agreement with those determined by the group-specific polymerase chain reaction, and none of the patients revealed a group opposite to that of hepatitis C virus genotype. The detection rate of the serological genotyping assay (89 of 91; 98%) was even higher than that of the polymerase chain reaction assay (78 of 91; 86%).(ABSTRACT TRUNCATED AT 250 WORDS)

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