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At present, routine screening for hepatitis C virus (HCV) infection is based on the detection of antiviral antibodies. Underdiagnosis of HCV infection by using HCV antibody tests, however, still occurs. Additional diagnostic means are provided by the polymerase chain reaction (PCR). The measurement of aminotransferase (ASAT and ALAT) has served as an auxiliary, less specific test. The present research aimed to design practical and low cost strategies to diminish underdiagnosis of HCV infection in dialysis patients. With this purpose in mind, we examined whether aminotransferases values in HCV antibody-negative patients could be related to undiagnosed HCV infection, by using HCV RNA testing by PCR as the gold standard. In 112 hemodialysis patients, we found 78 negative and 34 positive for HCV antibodies. A major finding was that 222 (28.2%) out of the 78 HCV antibodies-negative patients had positive HCV RNA by PCR. In repeated samples taken at six months follow-up from 19 out of these 22 patients, only one of them was positive for anti-HCV antibodies; moreover, a positive HCV RNA by PCR was confirmed in 13 (68.5%) of them. Within the HCV antibody-negative group, the mean values of ASAT, ALAT and gammaglutamiltransferase were higher (P < 0.001, P < 0.001 and P < 0.02, respectively) in the HCV PCR-positive versus the HCV PCR-negative patients. No significant differences were found in the liver enzyme values between the HCV antibody-negative, HCV RNA positive and the HCV antibody positive, HCV RNA positive individuals. Histological samples from two HCV RNA positive, HCV antibody-negative patients disclosed the presence of a mild liver disease. In conclusion, the present study demonstrates the critical importance of HCV RNA determination by PCR in hemodialysis patients who have no detectable circulating antibodies against the HCV. Furthermore, in conditions in which PCR technology is not readily available, we have established that the existence of a moderate increase of aminotransferases is a helpful clue to detect patients with absent HCV antibodies, and might represent an useful, low cost tool for HCV screening in dialysis patients.

To investigate the replicative hepatitis C virus status and its relation to liver damage, serum, peripheral blood mononuclear cells and liver-paired samples from 45 untreated hepatitis C virus infected patients (38 with chronic hepatitis, three with minimal changes, and four with normal liver) were studied by nested polymerase chain reaction, using primers from the 5' untranslated region. Positive HCV-RNA strand was detected in serum (69%), peripheral blood mononuclear cells (100%) and liver samples (100%). The presence of negative HCV-RNA strand was confirmed using specificity controls assays and was only detected in liver and peripheral blood mononuclear cells samples, (95% and 82%, respectively). No correlation between the presence of negative HCV-RNA strand in peripheral blood mononuclear cells and positive HCV-RNA strand in serum was found, whereas serum HCV-RNA was not detected in patients without negative HCV-RNA strand in the liver. Both positive and negative HCV-RNA strands were found in liver and peripheral blood mononuclear cells of four patients with normal liver histology, and three with minimal changes. Furthermore, the presence of HCV-RNA in serum did not correlate with the alanine aminotransferase values and the histological activity index. These data confirm the existence of replicative intermediates in the liver, not only from patients with histologically proven chronic hepatitis, but also from those with normal liver, suggesting the existence of hepatitis C virus in true healthy carriers.

Interferon (IFN) therapy of chronic hepatitis C has proved useful in recent years. A major goal in the treatment of hepatitis C is the prevention of the high relapse rate after cessation of therapy and the improvement of the response rate in non-responders. Several approaches can be tried. The administration of higher doses of IFN results in an increase in the response rate, but does not prevent ultimate relapse. Similarly, prolongation of the treatment period gives better results, but one third of cases still relapse. In these cases, re-treatment results in ALT normalization once again, but does not prevent subsequent relapse; in non-responders to IFN, re-treatment will not lead to improvement of the response rate. Analysis of the viral genome reveals its presence in serum in spite of the normalization of ALT values. The role of HCV genome heterogeneity in the response to IFN needs to be assessed and it is necessary to find other antiviral agents that are able to clear HCV from all relevant hosts (serum, liver tissue and mononuclear cells).