Chemiluminescence assay improves specificity of hepatitis C antibody detection. Clin. Chem

have typically been detected by enzyme immunoassay (EIA). A chemiluminescence assay (CA) for anti-HCV is now commercially available. Methods: We compared the positive rate for a CA in a HCV screening program for veterans with historical rates obtained with EIA. We also compared results in 2824 samples tested by both methods and assessed the significance of low signal-to-cutoff (S/C) ratios. Results: The frequency of CA-positive results was signif-icantly lower than with EIA (12.6 % vs 16.0%; P <0.0001). The frequency of low S/C ratios was also significantly lower with CA (11.5 % vs 20.0%; P <0.0001). Among low-positive values, samples positive by CA were significantly less likely to be recombinant immunoblot assay (RIBA)-negative (64 % vs 84%; P <0.0005). In parallel testing