Analysis of sera indeterminate by Ortho-HCV RIBA-2 by using three confirmatory assays for anti-hepatitis C virus antibody

Nanotechnology: A reality for diagnosis of HCV infectious disease

Hepatitis C virus (HCV) is the primary etiologic agent of liver cirrhosis or hepatocellular carcinoma. HCV elevated infection rates are mostly due to the lack of an accurate and accessible screening and diagnosis, especially in low- and middle-income countries. Conventional HCV diagnostic algorithm consists of a serological test followed by a nucleic acid test. This sequence of tests is time consuming and not affordable for low-resource settings. Nanotechnology have introduced new promising tests for the diagnose of infectious diseases. Based on the employment of nanoparticles and other nanomaterials which lead to highly sensitive and specific nanoscale tests, most of them target pathogen genome. Implementation of nanoscale tests, which are affordable, portable and easy to use by non-specialized personal, would improve HCV diagnosis algorithm. In this review, we have summed up the current emerging nanotechnology tools, which will improve actual screening and treatment programs, and help to reach HCV elimination proposal.

Estimating incidence rates with misclassified disease status: a likelihood-based approach, with application to hepatitis C virus

BACKGROUND

In epidemiologic research, incidence is often estimated from data arising from an imperfect diagnostic test performed at unequally spaced intervals over time.

METHODS

We developed a likelihood-based method to estimate incidence when disease status is measured imperfectly and assays are performed at multiple unequally spaced visits. We assumed conditional independence, no remission, known constant levels of sensitivity and specificity, and constant incidence rates over time. The method performance was evaluated by examining its bias, accuracy (i.e., mean squared error (MSE)), and coverage probability in a simulation study of 4000 datasets, and then we applied the proposed method to a study of hepatitis C virus (HCV) infection in a cohort of pregnant women in the period 1997-2006.

RESULTS

The simulation revealed that our method has minimal bias and low MSE, as well as good coverage probability of the resulting confidence intervals. In the application to HCV study, the standard incidence rate estimate which ignores the imperfections of the diagnostic test (number of events/person-years), was 13.7 new HCV cases per 1000 person-years (95% confidence interval 10.1, 17.4). The adjusted incidence estimates (obtained using our proposed method) ranged from 0.4 cases per 1000 person-years (when sensitivity and specificity were assumed to both be 95%) to 13.7 cases per 1000 person-years (when sensitivity and specificity were both 100%). The magnitude of difference between standard and adjusted estimates varied depending on specificity and sensitivity assumptions. Specificity had the greatest impact on the magnitude of bias.

CONCLUSIONS

Scientists should be aware of the impact of misclassification on incidence estimates. Appropriate study design, proper selection of the diagnostic test, and adjustment for misclassification probabilities in the analysis is necessary to obtain the most accurate incidence estimates.

Development of low cost peptide-based anti-hepatitis C virus screening and confirmatory assays: comparison with commercially available tests

Screening and confirmatory low cost reagent tests have been developed for detection of anti-hepatitis C virus (HCV). Assays are based on the use of specific synthetic peptides from several structural and non-structural viral proteins. The efficacy of the screening anti-HCV EIA-Spep assay was compared with both Abbott EIA 2.0 (Abbott Laboratories, North Chicago, IL) and Ortho EIA 2.0 (Ortho Diagnostic Systems, Raritan, NJ) anti-HCV detection kits and the confirmatory EIA-Cpep assay was compared with the Abbott Matrix anti-HCV confirmation test. In the EIA-Spep, a pool of 3 peptides was added to each well of a microtiter plate. In EIA-Cpep, each well was separately coated with 1 of 4 peptides and 1 recombinant protein. A total of 867 blood donor samples from Costa Rica tested simultaneously with the 3 screening assays yielded the same specificity and negative predictive values of > or =99.9% and 100%, respectively. A comparative study on voluntary blood donor samples from Honduras, Nicaragua, and El Salvador using the 2 anti-HCV confirmatory assays revealed different patterns that are 46% positive, 24% indeterminate, and 30% negative with the EIA-Cpep assay vs. 31% positive, 48% indeterminate, and 21% negative with the Matrix assay. A study of 71 patient samples from Costa Rica showed a higher correlation between initially reactive samples when analyzed by the Abbott and Ortho kits, than when the assay results were compared between the Abbott and EIA-Spep kits; the latter detected 7 and 15 non-reactive samples, respectively. These results could reflect the use of a similar antigen source for the 2 commercial assays. The presence of HCV RNA in a group of 29 samples analyzed was related to the simultaneous reactivity in all 3 screening assays. None of the discordant samples had detectable levels of HCV RNA. Economic difficulties for health care services in the developing countries of Central America have prevented implementation of routine anti-HCV blood donor screening tests. This is likely to be the primary reason for uncontrolled dissemination of HCV, and the lack of identification of potential high risk groups. Alternative low cost reagents developed locally as described in this article could be a useful tool in the control of HCV spread throughout the developing world.

Detection of hepatitis C virus by PCR in second-generation enzyme immunoassay-seropositive blood donors by using matched pairs of fresh frozen plasma and pilot tube sera

Between April 1993 and March 1995, 429 of 334,454 (0.13%) blood donations at the Toronto Centre of the Canadian Red Cross were reactive for hepatitis C virus (HCV) by second-generation enzyme immunoassay (EIA-2). Of the 429 EIA-2-positive donations, 189 (44%), 138 (32%), and 102 (24%) were positive, indeterminate, and negative by Second-Generation Recombinant Immunoblot Assay (RIBA-2). To assess HCV viremia and minimize the risk that specimen handling affected PCR-based detection, the qualitative AMPLICOR HCV test was performed on both pilot tube sera (PTS) and the corresponding fresh frozen plasma (FFP) from 294 EIA-2-reactive donations. AMPLICOR PCR results for PTS and FFP were 100% concordant and were confirmed by nested HCV PCR for 27 of 294 donations. The AMPLICOR HCV test was positive for 127 of 140 (91%) of RIBA-2-positive donations (81, 91, and 96% of donations with two, three, and four reactive bands, respectively), 5 of 88 (5.7%) indeterminate donations, and 0 of 66 (0%) RIBA-2-negative donations. The Third-Generation Recombinant Immunoblot Assay (RIBA-3) was performed on RIBA-2-negative, -indeterminate, and -positive, PCR-negative donations. RIBA-3 demonstrated enhanced specificity and resolved 18 of 88 (20%) of RIBA-2-indeterminate samples as HCV antibody positive. The study demonstrates that PTS are as suitable as FFP for PCR-based detection of HCV and can be used to determine if EIA-2-reactive blood donors are viremic at the time of donation.

Hepatitis C virus infection in an HIV-positive population in Normandy: antibodies, HCV RNA and genotype prevalence

The prevalence and the characteristics of hepatitis C virus infection (HCV) in 161 HIV-positive patients were studied. HCV seroprevalence was determined by enzyme immunoassay and recombinant immunoblot assay (RIBA). Two different reverse transcriptase polymerase chain reaction (RT-PCR) methods were also used to test the HCV-seropositive samples and 50 EIA-negative sera used as controls. The RNA HCV-positive sera were genotyped by the LiPA procedure. Associations of HCV status with demographic characteristics and risk factors were assessed by chi 2 and Fisher's exact tests. The seroprevalence of HCV was 34.2% with a significant difference between blood and sexual exposure risk groups (60.6% vs. 13.6%, respectively; P < 0.0001). Thirty-six of the 55 anti-HCV-positive sera were also positive for HCV RNA, and PCR detected HCV RNA in 8 HCV-seronegative patients. Various RIBA profiles were found and all sera were positive for antibodies to the c33 protein. A proportion of sera had elevated levels of transaminase activity (37.2%), and abnormal liver function as associated with HCV infection. Forty-two samples were genotyped and five genotypes and subtypes of the HCV virus were detected. Genotype 1a was the most frequent in this cohort, although genotype 1b is generally more common in France. The majority (94.1%) of the patients with genotype 1a had a history of blood exposure, which may account for the difference.