Long-term follow-up study of serum IgM antibody to hepatitis C virus (HCV), HCV replication, and liver disease outcome in chronic hepatitis C.

IgM anti-hepatitis C virus (HCV) and HCV RNA were longitudinally tested for 4.0-8.7 years in 40 patients with chronic HCV infection. Patients in disease remission usually lost IgM anti-HCV and HCV RNA, but most patients experiencing disease reactivation had increased levels of the IgM antibody or it reappeared before the biochemical relapse, even when HCV RNA was undetectable. IgM anti-HCV was detectable in most patients with ongoing viral replication and persistent liver disease. Despite long-term disease remission, IgM anti-HCV may persist and be detectable with or without evidence of serum HCV RNA; this indicates a possible disease reactivation, which could occur after several years of sustained transaminase normalization. Detection of IgM anti-HCV in chronic hepatitis C indicates an active immune response to persistent viral infection and should, therefore, be considered as a sensitive marker of active HCV replication and HCV-associated liver disease.