Hepatitis C virus infection, alpha interferon therapy and thyroid dysfunction

Abstract

positive anti-thyroid autoantibodies without biochemical evidence of thyroid dysfunction (8). HCV infection was confirmed by detectable serum HCV RNA using nested polymerase chain reaction (PCR) in five of six patients tested with anti-HCV antibodies. The 7% prevalence of anti-HCV positivity in the 147 patients was greater than the prevalence observed in a group of blood donors (0.7%). These observations suggest a possible role of HCV in autoimmune thyroid disease. Recently, Tran et al. (9) found higher levels of anti-Gor in patients with chronic hepatitis C and in patients with positive anti-thyroid autoantibodies as compared with those without anti-thyroid autoantibodies, which supports the existence of autoimmune disorders in these patients. All these studies must be interpreted according to the specificity of the test for the detection of anti-HCV antibodies and anti-thyroid autoantibodies. False positive anti-HCV results may be found in patients with autoimmune disease because of dysglobulinemia, in particular hypergammaglobulinemia (10). False positive results are less frequent with the secondgeneration ELISA than with the first-generation ELISA; however, false positive results are not rare in studies performed on frozen serum. With the thirdgeneration ELISA, the rate of false positive reactions is still lower (11). RIBA is more specific than ELISA; however, non-reactivity remains possible. In the study by Duclos-Vallee et al. (7), the presence of anti-HCV was confirmed by RIBA in four of six patients, but there was no confirmatory study by detection of serum HCV RNA. In the study by Quaranta et al. (8), antiHCV were detected using first- and second-generation ELISA without confimation by RIBA; however, HCV infection was confirmed in five of six patients by detection of serum HCV RNA by PCR. In our experience, in a series of 30 patients with Hashimoto’s disease, none had detectable anti-HCV using third-generation ELISA (unpublished data).