Background. For many people infected with the hepatitis C virus (HCV), the route of exposure, risk of transmission, and severity of associated liver disease are unknown. We studied these variables in people who donated blood voluntarily. Methods. Blood donors who tested positive for HCV antibodies on enzyme immunoassay were classified according to whether the results of a confirmatory second-generation recombinant immunoblot assay (RIBA) for HCV were positive, negative, or indeterminate. The evaluations also included an assessment of risk factors, a physical examination, serial determinations of alanine aminotransferase levels and HCV serologic assays, a polymerase- chain-reaction assay for HCV RNA, testing of sexual contacts and family members, and liver biopsies in some participants who were HCV-positive by RIBA. Results. A total of 481 donors were studied, among whom 248 were positive for HCV by RIBA, 102 had indeterminate results, and 131 were HCV- negative. In a logistic-regression analysis, significant risk factors for HCV infection among the HCV-positive participants were a history of blood transfusion in 66 (27 percent; P<0.001 for the comparison with RIBA-negative donors), intranasal cocaine use in 169 (68 percent, P<0.001), intravenous drug use in 103 (42 percent, P=0.001), sexual promiscuity in 132 (53 percent, P = 0.002), and ear piercing among men (P<0.05). Nine of 85 sexual partners of HCV-positive donors were anti-HCV-positive; 8 had used intravenous drugs or received transfusions. HCV RNA was found in 213 HCV-positive donors (86 percent), 3 who had indeterminate results by RIBA (2 of these 3 tested positive with a more specific, third-generation RIBA), and none who were HCV- negative. Of the HCV-positive donors, 69 percent had biochemical evidence of chronic liver disease; among 77 donors positive for HCV by RIBA who underwent liver biopsy, 5 had severe chronic hepatitis or cirrhosis, 66 had mild-to- moderate chronic hepatitis, and 6 had no evidence of hepatitis. Conclusions. Among volunteer blood donors, prior blood transfusion, intranasal cocaine use, intravenous drug use, sexual promiscuity, and ear piercing in men are risk factors for HCV infection. The high frequency of intravenous drug use was unexpected, because these donors had denied such use when questioned directly at the time of their blood donations.
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