Update on Status of HCV Testing

Robert Dufour, M.D., chief of pathology and laboratory medicine at the Veterans' Affairs Medical Center in Washington, DC (USA), during the annual meeting of the American Association of Clinical Chemistry in Orlando (AACC, FL, USA). A summary of Dr. Dufour's remarks follows.

HCV is the most common chronic infectious disease in Europe and North America. There are six different genotypes of the virus. To date, it has not been possible to grow the virus in culture. The most widely used test is designed to detect antibodies to one or more HCV proteins. Most laboratories report results as positive or negative, but the US Centers for Disease Control and Prevention have developed new guidelines that will require labs to separate low positives from strong positives and conduct follow-up testing before reporting results to a doctor.

To find if the person is currently infected requires an HCV RNA test. There are two major types, one qualitative and one quantitative. Tests have now been developed to determine the genotype. Most rely on detecting sequences in the RNA that correspond to those of the six known strains. The simplest, called a line probe assay (LiPA), involves immobilized HCV RNA sequences that are allowed to hybridize to RNA in the sample, with visual detection of hybrids by an enzyme reaction. The pattern of bands allows determination of genotype in most cases. Direct sequencing of a segment of the HCV genome and comparison to libraries of known genotypes allow detection of infection by more than one strain.

There are three potential treatments: interferon monotherapy, standard interferon plus ribaviron, and pegylated interferon plus ribavirin. Combination treatments are more effective than interferon monotherapy. Interferon treatment is expensive and has many side effects, so it is important to use sensitive assays to determine whether the treatment is effective in eliminating HCV RNA from the blood. The goal of treatment is to eradicate HCV RNA from the body, which correlates with the absence of HCV RNA in the blood after treatment has been stopped for six months.