Hepatitis C virus confirmation in blood donor screening

Supplementary anti-hepatitis C virus (HCV) testing with 2nd and 3rd generation recombinant immunoblot assay and matrix applied to enzyme immunoassay positive sera and comparison with HCV-RNA detection

A series of 118 serum samples tested positive in the anti-hepatitis C virus (HCV) 2nd-generation enzyme immunoassay (EIA-2), and indeterminate (93 samples) or negative (25 samples) in the supplementary 2nd-generation recombinant immunoblot assay (RIBA-2). These sera were further evaluated by three additional tests: 3rd-generation RIBA (RIBA-3), MATRIX, and AMPLICOR HCV-PCR. For the 93 RIBA-2 indeterminate serum samples, the results of the immunoassays had a concordance of 69%. Twenty-one and 34 samples remained anti-HCV indeterminate in the RIBA-3 test and the MATRIX, respectively. Among the 25 RIBA-2-negative samples, only seven samples remained anti-HCV negative, while five samples tested anti-HCV positive in both RIBA-3 and MATRIX. The reactivity of the RIBA-3 antigen NS5 was not crucial for the result of any sample. Positive to negative contradictions between the results of MATRIX and RIBA-3 were never observed. Altogether, the MATRIX tested a significantly lower number of samples anti-HCV negative than did the RIBA-3. HCV RNA was detectable in 54/93 RIBA-2 indeterminate and 7/25 RIBA-2 negative samples. High percentages of PCR positive results among RIBA-3-indeterminate and among MATRIX-indeterminate samples indicate an increased possibility of detecting HCV RNA if at least one antigen is reactive. The type of antigen, the pattern of antigen reactivity, or the level of reactivity had no prognostic value in predicting the presence of HCV RNA. Our findings show the necessity of being cautious in the interpretation of RIBA-2-negative results.

Analytical and laboratory evaluation of a new fully-automated third generation enzyme immunoassay for the detection of antibodies to the hepatitis C virus

An analytical and laboratory evaluation of a newly-developed fully-automated third generation ELISA for the detection of anti-HCV (Cobas Core Anti-HCV EIA, Roche) was undertaken. Coefficients of variation (CVs) calculated on positive control and serum samples ranged from 5.9 to 9.8% in the intra-assay precision test and from 3.9 to 11.3% in the inter-assay evaluation. With regard to the study of clinical laboratory performance, five groups of sera pre-screened with two third generation ELISA (Ortho HCV 3.0 ELISA; Innotest HCV Ab III) were assayed: anti-HCV negative samples (n = 932); anti-HCV positive samples (n = 449); difficult sera of different origin (n = 113); sera with discrepant results in the two ELISAs (n = 50); sera with an indeterminate result in one or more confirmatory test (n = 34). The overall concordance between the Roche anti-HCV EIA and the two reference assays was 97.5 and 97.8% for the Ortho and for the Innogenetics assays, respectively. Although it is not possible to provide absolute figures for clinical sensitivity and specificity, the results of the study on discrepant samples show that the Cobas Core Anti-HCV gives a number of negative results with positive or indeterminate confirmatory anti-HCV tests, which is intermediate between the Ortho and the Innogenetics assay. In contrast, only 5% Cobas Core Anti-HCV reactive sera are not positive or clear-cut single band reactive by supplemental assays. The results show that the new fully-automated third generation anti-HCV test is a valid alternative to other commercially available assays for screening of antibodies to the hepatitis C virus.

HCV-Infection in blood donors: association between anti-HCV core IgM antibodies and serum HCV RNA

Among 47 blood donors tested positive with HCV EIA 2.0 Abbott, 27 (57.4%) also reacted with four ¿third-generation' EIAs. The presence of anti-HCV antibodies was confirmed with 3 different immunoblot assays in 16 of 27 sera (34.0%) while 10 samples (21.3%) had indeterminate profile with antibodies usually directed against structural core antigen. Anti-HCV core IgM response was found in 12 of 47 sera (25.5%) and HCV viremia detected by the polymerase chain reaction (PCR) procedure was observed in 15 samples (31.9%). A comparative study of the different markers confirmed a good correlation between a strong antibody response in EIAs and immunoblot assays and the presence of HCV RNA in the serum; only 2 immunoblot indeterminate samples were PCR positive. An association was observed between IgM antibodies against "core' epitopes and HCV RNA carriage: all IgM-positive sera were found positive by PCR. However, the direct detection of viral genome remains the best method for identifying HCV carriers in the blood donor population.

Evaluation of a new automated third-generation anti-HCV enzyme immunoassay

The new Cobas Core Anti-HCV EIA was evaluated in two centers for its ability to detect antibodies directed to hepatitis C virus in human serum. This assay, which can be run fully automated on a random access analyzer, was compared with three other commercially available screening tests: the Ortho HCV 3.0 ELISA, the Murex anti-HCV, and the Abbott HCV EIA second generation. Positive or discrepant results were further investigated using the Wellcozyme HCV Western Blot or the Abbott Matrix HCV assays. The results obtained from analyzing 5045 serum samples showed a high correlation between the Cobas Core Anti-HCV EIA and the other screening assays, ranging from 98.9% to 99.9%. Diagnostic specificities and sensitivities ranged from 99.7% to 100% and from 98.8% to 100%, respectively. In this study, the Cobas Core Anti-HCV EIA proved to be a very convenient test, able to perform at the highest levels of sensitivity and specificity.

High proportion of false positive reactions among donors with anti-HCV antibodies in a low prevalence area

Among 39,656 voluntary blood donors in Okinawa Prefecture, Japan, 115 (0.29%) were repeatedly reactive for antibody to hepatitis C virus (anti-HCV) by second generation (2nd-gen) passive hemagglutination assay (PHA). Positive serum samples were tested for anti-HCV using three different enzyme immunosorbent assays (ELISAs; Abbott 2nd EIA, UBI-HCV-EIA, JCC-2) and for HCV-RNA by the polymerase chain reaction (PCR). The 115 2nd-gen PHA-positive sera were divided into three groups according to the agglutination titers; > 2(10) (high titer group), 2(7)-2(9) (median), 2(5)-2(6) (low). All but one serum (44/45) in the high PHA titer group reacted in each of the three second screening ELISAs. Furthermore, 43 (97.7%) of the 44 sera contained HCV-RNA by PCR. In the median titer group, 11 of the 13 samples tested were positive by each of the three ELISAs, and 4 (36.4%) of the 11 showed reaction by PCR. On the other hand, all of the 38 sera tested in the low titer group were negative for HCV-RNA by PCR, and 24 of the 38 were also negative by each of the three ELISAs. Most of the low titer positive reactions in the 2nd-gen agglutination assay seemed to be false positive. In Okinawa Prefecture, the prevalence of anti-HCV among blood donors is much lower than in the rest of Japan (0.29% vs. 1.11%). Moreover, a significant proportion of these sera were low titer by the PHA assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization and reactivity of an immunodominant domain in the NS3 region of hepatitis C virus

Analysis of the amino acid sequences of the nonstructural region 3 (NS3) of the hepatitis C virus type 1 revealed four points with a high average hydrophilicity (Ah). Two of these potential antigenic sites were expressed in E. coli as short fragments. The first fragment of 91 residues (NS3f3: residues 1359-1449) harbors the hexapeptide K-K-K-C-D-E with an Ah of 2.33; the second fragment is 73 residues long (NS3f4: residues 1460-1532) and encompasses the heptapeptide R-S-N-R-R-G-R with an Ah of 1.79. Both fragments were expressed with truncated hepatitis B core (tHBc) as a carrier protein. The fusion proteins were purified from the bacterial lysates by affinity chromatography on immobilized monoclonal antibodies against HBc, and evaluated as antigens in an enzyme immunoassay for the detection of HCV antibodies. In a specificity control panel, reactivity with NS3f3 was only found in proven HCV carriers, while reactivity with NS3f4 was weak in HCV carriers but accounted for some of the nonspecific serological reactions. In a group of 48 genotyped HCV-infected volunteer blood donors, antibodies against NS3f3 were detected in 90% (27/30) of HCV-type 1 infections and in all HCV-type 4 infections (5/5).(ABSTRACT TRUNCATED AT 250 WORDS)

Third-generation hepatitis C virus tests in asymptomatic anti-HCV-positive blood donors

This study evaluated the performance of third-generation anti-HCV assays in blood donors who were positive by second-generation anti-HCV, and assessed any possible relationship between antibody patterns, HCV replication and liver damage. Fifty-two second-generation enzyme immunoassay-positive asymptomatic Italian blood donors were retested for anti-HCV by third-generation enzyme immunoassay and recombinant immunoblot assay (Ortho third-generation enzyme immunoassay, third-generation recombinant immunoblot assay), utilising recombinant C33c and NS5 and synthetic peptide C100 and C22 antigens, and for HCV-RNA by "nested" polymerase chain reaction with 5' region primers. Alanine aminotransferases were tested monthly for 6 months. Two out of 52 second-generation enzyme immunoassay-positive donors were third-generation enzyme immunoassay, third-generation recombinant immunoblot assay and HCV-RNA negative. Among 50 third-generation enzyme immunoassay-positive cases, two had a third-generation enzyme immunoassay optical density < or = 1: one was third-generation recombinant immunoblot assay and HCV-RNA negative, and the other was third-generation recombinant immunoblot assay "indeterminate" and HCV-RNA-positive. The remaining 48 cases had third-generation enzyme immunoassay optical density > 1: six were third-generation recombinant immunoblot assay negative (one HCV-RNA+ve), eight "indeterminate" (two HCV-RNA+ve) and 34 positive (22 HCV-RNA+ve). All "indeterminate" subjects reacted only to C22. HCV-RNA was positive in 22/34 cases with positive third-generation recombinant immunoblot assay (two or more Ags), 3/9 "indeterminate" and 1/11 negative. Alanine amino-transferases were abnormal in 13 cases with positive third-generation recombinant immunoblot assay, one was "indeterminate" and three were negative.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of third-generation screening and confirmatory assays for HCV antibodies

A third-generation (gen.) screening and immunoblot assay (Ortho EIA-3.0; Chiron RIBA-3 prototype), using antigens derived from the capsid and different nonstructural regions (NS3, NS4 and NS5) of the hepatitis C virus viral genome, were evaluated in comparison with the corresponding second-gen. assays (Ortho EIA-2.0; revised Ortho EIA-2.5; Chiron RIBA-2). In 203 depository sera of blood donors, positive in EIA-2.0, specificity of the screening assays was improved as shown by an increase in positive predictive value for viral carrier state from 0.23 (EIA-2.0) to 0.37 (EIA-2.5) and 0.52 (EIA-3.0). Comparing the confirmation patterns on RIBA-2 and RIBA-3, this amelioration was mainly due to the specific elimination of false-positive c22-3 and c100-3 reactions. Antibody response to the newly added NS5 antigen was not as prevalent as to the other antigens and had only a minor influence in sample allocation. In contrast, screening of 1,560 volunteer blood donors and 47 hemodialysis patients revealed 3 additional positive sera, only reacting with the NS5 antigen. However none of these isolated NS5 reactions could be confirmed on synthetic peptides [INNO-LIA: NS5(p)] and none was PCR positive. A documented seroconversion, detected earlier with EIA-3.0, was related to a better immunological response to the NS3 antigen and not to the additional NS5. From this pilot study third-gen. assays appeared extremely useful in the reevaluation of HCV-seropositive depository sera. However the additional value of the NS5 antigen in blood donor screening is still hypothetical and remains to be established in larger screening studies.