HEPATITIS C DISEASE : CLINICAL ASPECTS
The incubation period of hepatitis C averages 6–12 weeks. The infection is usually asymp-tomatic or mild and anicteric but results in a chronic carrier state in up to 85% of adults of patients. The average time from infection to the development of chronic hepatitis is 10–18 years. Cirrhosis and hepatocellular carcinoma are late sequelae of chronic hepatitis. Chronic hepatitis tends to wax and wane, is often asymptomatic, and may be associated with either elevated or normal alanine aminotransferase (ALT) values in serum. Chronic hepatitis C is the leading cause of liver transplantation in the United States.
Antigens of hepatitis C are not detectable in blood, so diagnostic tests attempt to demon-strate antibody. Unfortunately, the antibody responses in acute disease remain negative for 1 to 3 weeks after clinical onset and may never become positive in up to 20% of pa-tients with acute, resolving disease. Current tests measure antibodies to multiple hepatitis C antigens by either enzyme immunoassay or immunoblot testing. Even with these newer assays, IgG antibody to hepatitis C may not develop for up to 4 months, making the sero-diagnosis of acute hepatitis C difficult. Quantitative assays of hepatitis C RNA may be used for diagnosis, estimating prognosis, predicting interferon responsiveness, and moni-toring therapy, but there is not a very good correlation between viral load and histology.
Combination therapy with interferon alpha and ribavirin is the current treatment of choice for patients with evidence of hepatitis due to hepatitis C. Criteria for initiating treatment are controversial, but most physicians would treat with abnormal liver histology and ele-vated liver enzymes. Responses are better in patients with genotypes other than 1 and those with low initial titers of viral RNA. Corticosteroids are not beneficial. Avoidance of injection drug use and screening of blood products are important preventive measures. It is not clear whether prophylactic ISG protects against hepatitis C. In addition, it is question-able whether a vaccine will be effective; patients may be reinfected by wild-type virus.