Significance of anti-hepatitis C virus core IgM antibodies in patients with chronic hepatitis C.

Antihepatitis C virus (HCV) IgM antibodies were found in patients with both acute and chronic hepatitis C. The aims of the study were to determine the significance, in terms of liver disease and virological parameters, of anti-HCV core IgM antibodies in the serum of patients with chronic hepatitis C, and the possible relationship between the presence of these antibodies before treatment and biochemical and virological responses to interferon therapy. Sixty-one patients with chronic hepatitis C were studied. Tests for serum anti-HCV core IgM antibodies were carried out before treatment. The patients received 3 mega units of interferon alpha-2a subcutaneously thrice weekly for at least 3 months (6 months when alanine aminotransferase activity was normal at month 3). A biochemical response to interferon therapy was defined as normal alanine aminotransferase activity at the end of treatment (month 6: biochemical response) and 6 months later (month 12: sustained biochemical response). A sustained virological response was defined as serum HCV RNA negativity by a polymerase chain reaction-based detection method (PCR) in patients with normal alanine aminotransferase at month 12. Anti-HCV core IgM antibodies were detected in 28 of the 61 patients (46%). The prevalence of these antibodies was significantly higher in patients infected with HCV genotype 1 (including subtypes 1a and 1b) than in patients infected with other genotypes (including 2a and 3a) (57% vs. 17%; P < 0.01). No significant difference was found between IgM-positive and IgM-negative patients as regards the mean age, sex ratio, serum alanine aminotransferase and gamma-glutamyl transpeptidase activities, the prevalence of cirrhosis in liver biopsy specimens, detection of HCV RNA by PCR, and quantitation by branched DNA assay. At month 6 of interferon therapy, normal alanine aminotransferase activity was significantly more frequent in IgM-negative than in IgM-positive patients (52% vs. 21%, respectively; P < 0.02). At month 12, normal alanine aminotransferase activity and PCR negativity were significantly more frequent in IgM-negative than in IgM-positive patients (18% vs. 0%, P < 0.04). It is concluded that anti-HCV core IgM antibodies in serum are significantly more frequent in patients infected by HCV type 1 than by other types. This suggests that their overall prevalence in patients with chronic hepatitis C in industrialized countries, where HCV type 1 accounts for the majority of infections, would be of the order of 50%, that anti-HCV core IgM antibodies are not associated with characteristic features of liver disease, and that their presence before treatment is associated with a failure of interferon alpha therapy to clear the virus.

Is the detection of anti-hepatitis C virus core IgM influenced by the presence of serum rheumatoid factor?

Rheumatoid factor (RF) induces false-positive results in the detection of serum antibodies, especially of the IgM type. About 70% of the patients with chronic hepatitis C have abnormal levels of serum RF. The aim of this study was to determine whether the presence of serum RF could influence the detection of anti-HCV core IgM, using an assay designed not to pick up RFs by the addition of goat antibodies directed against human IgG in the sample diluent. Serum anti-HCV core IgM antibodies and RF were sought in 60 patients with chronic hepatitis C. Serum anti-HCV IgG antibodies and anti-HCV core IgM antibodies were also sought in 101 patients with high levels of RF. Anti-HCV core IgM antibodies were found in 45% and serum RF in 72% of the patients with chronic hepatitis C. Neither the prevalence nor the levels of RF differed significantly between IgM positive and negative patients. Eight percent of the 101 patients with raised RF had anti-HCV antibodies and two of them had anti-HCV core IgM antibodies. No patient without anti-HCV antibodies had anti-HCV core IgM antibodies. These results show that: a) the detection of anti-HCV core IgM in patients with chronic hepatitis C is independent of the presence of serum RF; b) high titers of serum RF are not responsible for false-positive results of anti-HCV IgM tests. The study suggests that the test used could be a confident tool for studies on the significance of anti-HCV core IgM antibodies in chronic hepatitis C.