The methods for diagnosing hepatitis C virus infection have been evolving since the first-generation enzyme-linked immunosorbent assay antibody test was devised in 1989. In addition to assaying for serum antibodies against viral proteins, serum and liver tissue can be tested for viral RNA, evidence of ongoing viral replication. The improving ability to diagnose hepatitis C has furthered the understanding of the natural history of this infection. Acute hepatitis C results in chronic elevations of serum transaminase levels following nearly one half of cases. Cirrhosis complicates approximately 20% of chronic infections. Long-standing chronic hepatitis C may play a role in the pathogenesis of hepatocellular carcinoma. Sustained normalization of serum transaminase levels, often accompanied by a decrease in or disappearance of viral RNA, occurs in approximately 25% of patients with chronic hepatitis C who are treated with a 6-month course of recombinant interferon alfa. This treatment can occasionally be complicated by hematologic, endocrinologic, and psychiatric adverse effects but is usually fairly well tolerated. Whether interferon therapy will diminish the risk of cirrhosis or carcinoma is not yet known. This article reviews the diagnosis of chronic hepatitis C infection as well as the mechanisms of action, efficacy, and adverse effects associated with interferon alfa therapy.
