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We titrated 277 hepatitis C virus (HCV) antibody-positive serum samples from 235 volunteer blood donors as well as from 42 outpatients of a hospital for elderly people and studied the relation of the titre of HCV antibody to the presence of HCV RNA, of antibody to C100 protein (anti-c100) and of antibody to GOR epitope (anti-GOR). Liver dysfunction was measured also. Of 177 HCV RNA-positive serum samples, 87 were tested for the degree of HCV viraemia by means of a competitive assay. Among the 277 samples, prevalences of HCV RNA, anti-c100, anti-GOR and liver dysfunction were 63.9%, 71.8%, 75.7% and 17.5%, respectively. The prevalence of HCV RNA became higher as the titre of HCV antibody increased. The titre tended to increase with age but the tendency was not statistically significant. The mean titre was higher in females (2(10.4 +/- 1.8)) than in males (2(9.4 +/- 2.2)) (P < 0.01). In the HCV RNA-positive serum samples, the HCV antibody titre was significantly higher in the anti-c100-positive samples than in the negative ones. This difference between the positive and negative samples, however, was not statistically significant for anti-GOR and liver dysfunction. Low degrees of HCV viraemia were accompanied by high titres of HCV antibody while high degrees of HCV viraemia went with low titres of HCV antibody. The study revealed that titres of HCV antibody were higher in females and the degree of HCV viraemia correlated inversely with the titre of HCV antibody.

A second generation assay for antibody to hepatitis C virus (anti-HCV) was used in order to establish the exact prevalence of HCV infection in haemodialysis patients. HCV RNA was sought by the polymerase chain reaction in order to determine whether haemodialysis patients with anti-HCV had been infected with HCV in the past or were presently infected. Of 357 patients, 198 (55.5%) were positive for anti-HCV, compared to 113 (31.7%) positive for original antibody to c100-3 protein (P < 0.001). HCV RNA was detected in 171 (86.4%) of the 198 patients with anti-HCV. Liver dysfunction was found in 63 (17.6%) of all haemodialysis patients. Of these, 55 (87.3%) had HCV infection, one (1.6%) hepatitis B virus infection while, in the remaining seven, the origin was unknown. Thus, in almost all anti-HCV-positive patients, HCV viraemia was present. We conclude that HCV is an important cause of liver disease in haemodialysis patients.

Serum samples from 337 Japanese patients with chronic non-A, non-B liver disease were tested for antibodies to hepatitis C virus (HCV) by means of first-generation (c100-3; anti-c100) and second-generation (pHCV-34, pHCV-31, c100-3; anti-HCV II) enzyme linked immunosorbent assays (ELISA) and for antibody to the GOR epitope (anti-GOR) also by ELISA. Anti-HCV II was detected in 314 (93.2%), anti-c100 in 247 (81.3%) and anti-GOR in 211 (62.6%) samples. Thus, anti-HCV II was more sensitive in detecting HCV infection than either anti-c100 or anti-GOR (P < 0.001). All serum samples reactive with anti-c100 or anti-GOR reacted with anti-HCV II. Among 314 anti-HCV II-positive patients, we found that 185 (58.9%) were positive for both anti-c100 and anti-GOR while 14 (4.5%) were positive for anti-HCV II alone. Nine (64.3%) of the 14 are presently infected with HCV, as revealed by detection of HCV RNA in their serum; the remaining five may have been infected in the past with HCV. These findings indicate that HCV is a major causative agent of chronic non-A, non-B liver disease in Japan and that detection of anti-HCV II is a specific and more sensitive diagnostic test for HCV infection.