Objective To evaluate the specificity and sensitivity of a Hove]hepatitis C virus NS3 antigen detection immunoassay and the potential application of this assay in clinical diagnosis.Methods Samples from 77 healthy flubjects,173 anti-HCV-positive pailents and 3708 patients infected with other type of hepatitis were tested with the HCV NS3 antigen assay,some HCV NS3 antigen positive samples were validated witll HCV-RNA.neutralization and immunodot assays.Twenty.five sequential samples from 11 HCV NS3 antigen positive patients were subjected to kinetic studv.Results Forty-eight(1.3%)of 3708 antiHCV negative samples were positive for HCV NS3 antigen.Among them,44 of 3030 samples from patients only infected with HBV were HCV NS3 antigen-positive,4 of the 445 samples from patients infected with other type hepatitis were HCV NS,antigen-positive.In addition.42(24.3%)of 173 anti-HCV positive samplea were HCV NS3 antigen-positive and all 77 samples from healthy subjects were negative to HCV NS3 antigen assay.Of 15 HCV NSl antigen-positive samples,9(60%)were HCV-RNA positive.The neutralization and positive percentage of immunodot assay for 23 HCV NS3 antigen-positive sera were 87.0%(20/23)and 69.6%(16/23) respectively.Of the 25 sequential samples from 11 HCV NS3 antigen positive patients,there was a negative correlation between the A values and the duration of test.and there were correlations among their HCV NS3 antigen.HCV.RNA and anti-HCV;In addition,the anti-HCV antibodies of two sera were detected while their A values of HCV NS3 antigen decreased gradually.Conclusion The HCV NS3 antigen detection assay showed perfect specificity and higher sensitivity,it will be useful in routine laboratories test in developing countfies for earlier diagnosis of HCV infection.

A simple rapid detection of antibody to hepatitis delta virus (anti-HDV) in human serum was developed by using double antigen sandwich ELISA. HDV gene fragment encoding HDAg was isolated from a Chinese patient infected with HDV by RT-PCR, and a high-efficient expression HD-PQE31 strain was constructed with the fragment. We obtained high titer and good quality hepatitis delta virus protein purified by Ni-NTA metal-affinity chromatography, which was identified by Western blot and ELISA, then we set up the double antigen sandwich ELISA for detection of anti-HDV in human serum, and the performance of the sandwich ELISA was evaluated in terms of specificity and sensitivity. Results were: 1) The purified HDAg protein's purity was 90%, and its ELISA titer was 1/100 000. 2) 42 anti-HDV positive sera were detected and showed that the sensitivity of sandwich ELISA was higher than that of competitive ELISA (t=2.44, p<0.01). 3) The inhibitory rates for 2 anti-HDV positive sera by the specific HDAg were 74% and 93% respectively. 4) For the assay of specificity, all 60 samples infected by other hepatitis viruses and 30 normal samples were negative for anti-HDV. These results suggested that the double antigen sandwich ELISA with purified recombinant HDAg showed higher specificity and sensitivity, It can be used in routine laboratories to diagnose the HDV infection.