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To understand how to prevent the diffusion of hepatitis C virus (HCV) in dialysis units, 289 chronic dialysis patients treated in a renal department from the beginning of 1990 to June 30, 1993, were studied. Patients were screened monthly for alanine aminotransferase values and every 3 months for anti-HCV antibodies. At the beginning of the study the prevalence of anti-HCV antibodies was 24.7%. Two study groups were defined. In the first, anti-HCV-positive patients were treated on separate machines; in the second, 13 anti-HCV-positive and 13 negative patients shared the same machines. Patients in the study were treated with traditional dialysis, employing low-permeability membranes and disposable dialysate circuits on machines without an ultrafiltration control device. The 'universal precautions' were rigorously applied. The use of blood transfusions was markedly reduced. Although new patients starting dialysis treatment revealed a high frequency of HCV positivity (10.8%), the overall prevalence of HCV infection in the department did not increase during the follow-up period. Furthermore, no seroconversion was found in patients on dialysis treatment, not only in the section where anti-HCV-positive patients were treated on separate machines, but also in the section where anti-HCV-positive and anti-HCV-negative patients shared the same machines. The possibility of an intradialytic diffusion of HCV appeared to be very low and the treatment of infected patients on separate machines not strictly necessary.

In 12 hemodialysis (HD) patients with persistently raised serum alanine amino-transferase concentrations, 6 of which with anti-HCV antibodies, a liver biopsy was performed. The histological examination showed chronic persistent hepatitis or less significant changes in 11 patients and mild chronic active hepatitis in only 1. Non-A, non-B hepatitis seems to demonstrate in HD patients a low tendency to induce an active and progressive liver disease.

To define the prevalence of non-A, non-B hepatitis, antibodies to HCV were detected in 193 patients on renal replacement therapy (52 transplant and 141 hemodialysis patients) and in 50 staff members of a Nephrology Department. Unequivocal seroconversion was documented in 5 transplant (9.6%) and in 26 dialysis patients (18.4%). In the dialysis population, the prevalence of anti-HCV antibodies was evaluated in patients grouped according to the number of blood transfusions and to the different sections of dialytic treatment. The most striking findings were the marked differences in the prevalence of anti-HCV antibodies among patients treated in different sections (from 0% to 70%), and the presence of a significant increase in alanine-amino-transferase (ALT) concentrations in 14 anti-HCV negative patients. The results suggest that the diffusion of non-A, non-B hepatitis is mainly transfusion-related, with the possibility of significant environmental diffusion related to the violation of infection-control measures. The current immunoassay is probably unable to detect the actual frequency of the infection.