Serological and molecular biology screening techniques for HVC infection

This is a review of the main biological tests that can be requested by nephrologists to diagnose hepatitis C virus infection, together with a tentative specification of their indications and interpretation methods. This diagnosis is mainly based on serological tests (ELISA). The second and third generation tests contain, in addition to the NS4, proteins of the core and NS3 region. The latter two proteins provided great specificity and are antigenically well preserved in most virus types. They constitute the backbone of serological screening systems. In parallel with ELISA, analytical tests have been developed. In the form of immunoblots, they use proteins similar to those of ELISA and permit separate reading of antibody response to each protein. To achieve serological results, biologists must use at least two different techniques. Several strategies for using the various tests are thus available. However, serological diagnosis has its limitations: acute hepatitis most often precedes seroconversion; the results do not date the disease nor do they specify infectivity, evolution or recovery; seronegativity does not exclude a positive diagnosis with any certainty, especially in such populations as haemodialysis patients. To make up for the shortcomings of serological tests, direct viral detection can be achieved by genic amplification, most often by polymerase chain reaction in the best preserved part of the genome (5' non-coding end). PCR is currently becoming the real reference test for hepatitis C diagnosis. It is also possible to quantify viraemia and to determine the viral genotype. The relevancy of these two factors to therapy is controversial. Immunohistochemical study of liver biopsy specimens is still little used.