Specificity and sensitivity of 3rd generation EIA for detection of HCV antibodies among intravenous drug-users.

Serum samples from 487 ambulatory I.V. drug users were screened for HIV and HCV antibodies to determine the prevalence of coinfection in this high risk group for AIDS. For anti-HCV antibody screening we first used a 3rd generation EIA using, as antigen synthetic peptides which were not subjected to false positive results due to antibodies against superoxide dismutase or against yeast proteins (which may copurify with the recombinant proteins employed in the first and second generation test). The specimens that were positive in the screening test were confirmed by a more specific EIA system that detect antibodies to proteins encoded by structural (HCV-st EIA) and non structural (HCV-nst-EIA) regions of the HCV genome. A second confirmation assay was also performed: sera were run in presence or absence of blocking reagents which inhibits antibodies to C200 and C22 HCV epitopes for binding to the solid phase. The sensitivity of the HCV EIA screening for human HCV antibody detection revealed a 100% positivity for HCV infection. The confirmatory strategy presented in this paper revealed an HCV EIA specificity of 98.6%. In this work we demonstrated a significantly higher prevalence (p < 0.001) of HCV exposure in HIV infected individuals compared to the general population. Our experimental data also confirmed that HBV infection in drug-users at high risk for HIV infection was significantly associated with HCV infection (p < 0.001). In contrast, the acquisition of HIV by sexual contact was not a statistically significant risk factor for HCV coinfection.