Abstract
The diagnostic efficacy of Ortho VITROS chemiluminescence assay (CIA) in detecting antibodies to the hepatitis C virus (HCV) and the clinical significance of specimens with low sample-to-cut off (S/Co) ratio was analysed, comparing the positive rate for CIA in 5,550 consecutive outpatients with enzyme-immunoassay (EIA). In parallel testing, 43 samples (0.8%) were low positive by CIA (S/Co ratio from 1.0 to 8.0) but negative by EIA. No samples CIA negative/EIA positive were found. Among EIA negative results we found 22 RIBA positive or indeterminate, yielding CIA sensitivities of 100% and EIA sensitivity of 97.8%. None of the 33 samples with CIA S/Co ratios of ≤ 2.0 and only 3 (10.7%) with S/Co ratios of between 2.1 and 8.0 were found to be RIBA positive. Instead, the majority of samples with S/Co ratios ≤ 8.0 (55.7%) were recombinant immunoblotting assay (RIBA) negative. HCV RNA and/ or clinical evidence of HCV infection was not found in any of the 12 indeterminate cases examined with S/Co ratios ≤ 2. We suggest to report them as “Borderline”, with the recommendation to follow up in the future. Key words: HCV infection, RIBA, HCV-RNA, CIA, EIA.
Highlights
Since their introduction in 1990, enzyme linked immunosorbent assays (EIAs) for antibodies to hepatitis C virus (HCV) have been the principal tests for detection of exposure to HCV
Of the 5,550 patients included in this study, 376 (7%) were repeatedly chemiluminescence assay (CIA) anti-HCV positive and 333 (6%) EIA positive
Comparing the diagnostic efficacy of the CIA and EIA tests, the results were concordant in 5,507 samples (5,174 negative in both the EIA and CIA, 93.6% and 333 positive in both assays, 6.0%) and discordant in 43 samples (0.8%)
Summary
Since their introduction in 1990, enzyme linked immunosorbent assays (EIAs) for antibodies to hepatitis C virus (HCV) have been the principal tests for detection of exposure to HCV. Usually reported as positive or negative, the results are measured as an absorbance signal that is compared with that of a cutoff value (S/C) (Courouce et al, 1991; Zhang et al, 1993; Goncales et al, 2000). It was demonstrated that falsepositive anti-HCV results by EIA are frequent in samples with S/C ratio < 3.8 (Dufour et al, 2003). American Centers for Disease Control and Prevention (CDC) recommend RIBA confirmation for these samples(Centers for Disease Control and Prevention, 2003). It was over ten years ago that a chemiluminescence assay (CIA) for anti-HCV has been developed by Ortho Clinical Diagnostics (Calcagno et al, 2001). The VITROS anti-HCV assay is a specific two-step sandwich CIA for
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