THE POLYMERASE CHAIN-REACTION AND HEPATITIS-C VIRUS DIAGNOSIS

In the absence of tissue culture, electron microscopy or assays for vi ral antigen, the direct detection of hepatitis C virus (HCV) is by nec essity dependent upon nucleic acid hybridisation methods. Of the avail able methods, amplification of HCV cDNA by polymerase chain reaction ( PCR) commends itself by virtue of its extreme sensitivity and its cons equent ability to detect the very low levels of HCV-RNA that are prese nt in many clinical samples. In this review the development and evolut ion of PCR techniques for HCV detection are described and a number of clinical applications are considered in detail. The applications inclu de diagnosis of acute infection during the seronegative window period prior to the appearance of HCV antibodies, and diagnosis of HCV infect ion in the immunosuppressed. PCR also enables identification of the ch ronic viraemic carrier stale and it permits accurate monitoring of the antiviral effects of drugs such as interferon. Confirmation of the sp ecificity of HCV antibody assays and detection of HCV contamination of blood donations and blood products are other important areas in which PCR techniques have proved invaluable. In addition, PCR-based techniq ues underlie an increasing number of molecular epidemiological and gen otyping studies and they are providing insights into the details of HC V cellular tropism and replication. A number of logistic problems and operational difficulties are also discussed. Despite these limitations it is concluded that PCR will continue to make significant contributi ons to both clinical practice and to our understanding of the basic bi ology of HCV infection.