Hepatitis C virus (HCV) core antigen assay to detect ongoing HCV infection in thai injection drug users

Comparing RT-qPCR and Hepatitis C Virus Antigen Detection Assay for Detecting Active Infection in Blood Donors in Fars Province, Iran

Background: Immunoassay is still used to detect hepatitis C virus (HCV) antibodies in donated blood in many developing countries. However, an immunoblotting confirmation test is needed to confirm positive results. Objectives: We compared the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of nucleic acid testing and HCV core antigen (HCVcAg) detection in the serum samples of blood donors with HCV antibodies to determine active infection. Methods: Overall, 90 serum samples from blood donors referred to Fars Blood Transfusion Organization, Iran during March 2017-March 2019 and initially tested for HCV antibodies were included in the study. Enzyme immunoassays were used to detect the HCV antigen and anti-HCV antibody. A commercial reverse transcription-polymerase chain reaction (RT-PCR) kit was used to quantify HCV RNA. The HCV genotypes were also determined by DNA sequencing. In order to compare the HCVcAg detection method with the RT-qPCR reference method, sensitivity, specificity, performance, PPV, and NPV were calculated. Results: Out of 90 serum samples, 73 were positive for anti-HCV antibody, and 17 sera were negative. The HCV RNA was detected in 60 (82%) of anti-HCV antibody-positive samples, whereas the HCVcAg test detected HCV antigen in 54 (74%) of the samples, indicating a significant correlation between the two assays (r = 0.86). The overall sensitivity and specificity for HCVcAg detection method were 93.85% [95% confidence interval (CI): 84.99 - 98.3%] and 100% (95% CI: 94.64 - 100%), respectively. Based on the statistical analysis, the accuracy of the antigen detection test was 94.83% (95% CI: 87.26 - 98.58%). Moreover, the agreement between HCV RNA detection using RT-qPCR and HCVcAg detection was 97.78% (kappa value: 0.94). Conclusions: The sensitivity and specificity of HCVcAg detection in blood donors were ideal compared to the RT-qPCR reference method. However, the method should be tested on more HCV antibody-positive and -negative samples. Furthermore, our study revealed a significant association between the number of RT-qPCR-positive cases and the cases diagnosed by the HCVcAg detection method for screening and detecting active HCV infection in blood donors.

Prevalence of HCV genotypes and subtypes in Southeast Asia: A systematic review and meta-analysis

Known for its high genetic diversity and variation in genotypic presence in different regions of the world, hepatitis C virus (HCV) is estimated to infect about 71 million people globally. Selection of an appropriate therapeutic regimen largely depends on the identification of the genotype responsible for the infection. This systematic review and meta-analysis was conducted to provide a comprehensive view of HCV genotype and subtype distribution in Southeast Asia (SEA). The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA). We searched five databases without year and language restrictions. Data from 90 eligible studies involving 15,089 genotypes and 9,646 subtypes representing 10 SEA countries were analyzed. The pooled estimates showed that genotype 1 (46.8%) [95% CI, 43.2–50.4; I² = 92.77%; p < 0.001] was the most dominant HCV genotype in the region, followed by genotype 3 (23.1%) [95% CI, 19.4–27.2; I² = 93.03%; p < 0.001], genotype 6 (16.5%) [95% CI, 13.8–19.6], genotype 2 (4.6%) [95% CI, 3.5–5.9], genotype 4 (1.1%) [95% CI, 0.7–1.5] and genotype 5 (0.8%) [95% CI, 0.4–1.3]. Philippines had the highest prevalence of genotypes 1 and 2. Genotype 6 became more prevalent after year 2000. Over 40 different subtypes were identified, with subtypes 1b (26.3%), 1a (21.3%), and 3a (14.3%) being the most prevalent of all the reported subtypes. Although on a global scale, genotype 6 is considered highly prevalent in SEA, evidence from this study reveals that it is the third most prevalent genotype within the region.

Hepatitis C virus infection among people who inject drugs in Bangkok, Thailand, 2005-2010

BACKGROUND

Approximately 1% of adults in Thailand are infected with hepatitis C virus (HCV). New direct-acting antiviral agents achieve sustained virologic responses in >95% of HCV-infected patients and are becoming available in countries around the world. To prepare for new HCV treatment options in Thailand, this study characterized HCV infections among people who inject drugs (PWID) in Bangkok.

METHODS

The Bangkok Tenofovir Study (BTS) was a pre-exposure prophylaxis trial conducted among PWID, 2005-2013. Blood specimens were randomly selected from PWID screened for the BTS, to test for anti-HCV antibody and HCV RNA. The HVR1 region was amplified by polymerase chain reaction, using multiplex primer sets with unique identifier sequences; amplification products were pooled in sets of 25; and consensus sequencing was performed to characterize individual HCV genotypes.

RESULTS

The median age of 3679 participants tested for anti-HCV antibody was 31 years, 3016 (82.0%) were male and 447 (12.2%) were HIV infected. The prevalence of anti-HCV antibody was 44.3%. The adjusted odds of testing positive for anti-HCV antibody were higher in men (adjusted odds ratio [aOR] 3.2, 95% confidence interval [CI] 2.4-4.3), those aged 40 years or older (aOR 2.7, 95% CI 2.1-3.5), those who had more than a primary school education (aOR 1.7, 95% CI 1.4-2.1), and those who tested HIV positive (aOR 5.2, 95% CI 3.7-7.4). HCV RNA was detected in 644 (81.3%) of the 792 anti-HCV antibody-positive specimens, yielding an HCV RNA-positive prevalence of 36.0% (95% CI 33.8-38.2). Among a random sample of 249 of the 644 specimens, 218 could be characterized, and the most common HCV subtypes were 1a (30.3%), 1b (12.8%), 3a (35.8%), 3b (6.9%) and 6n (8.7%).

CONCLUSION

The prevalence of anti-HCV antibody among PWID was 44.3% and more than one third (36.0%) were HCV RNA positive. Genotypes 1, 3 and 6 accounted for all typable infections. As the government of Thailand considers introduction of direct-acting antiviral medications for people with hepatitis C, it will be important to ensure that the medications target these subtypes.

Hepatitis C virus core antigen: A potential alternative to HCV RNA testing among persons with substance use disorders

BACKGROUND

The hepatitis C virus (HCV) core antigen (HCVcAg) may be an alternative diagnostic method to HCV RNA especially in populations such as substance users, the homeless or in resource-limited settings.

AIMS

To evaluate performance of HCVcAg test in patients with opioid use disorder (OUD) on methadone in order to document its performance characteristics in the target population and to ensure that its specificity remains consistent across different populations.

METHODS

HCVcAg levels from 109 methadone-maintained patients were compared to HCV RNA levels.

RESULTS

Mean age was 53.8±7.8years, 59.6% were male, 68.8% African American, and 44% HCV-infected. HCVcAg was detectable in 47 of 48 HCV-infected, and undetectable in all HCV RNA negative patients. The HCVcAg assay had sensitivity of 97.9% and specificity of 100%. Correlation with HCV RNA levels was excellent (r=0.88, 95% CI 0.76; 0.95, p<0.01).

CONCLUSION

HCVcAg has excellent performance for the diagnosis of HCV infection in patients with OUD on methadone.

Can Hepatitis C Virus Antigen Testing Replace Ribonucleic Acid Polymearse Chain Reaction Analysis for Detecting Hepatitis C Virus? A Systematic Review

The complexity and cost of current diagnostics for hepatitis C virus (HCV) may act as a prevention to the scale-up of treatment in the developing world. Currently, ribonucleic acid (RNA)-polymerase chain reaction tests are the gold standard. However, there is potential for the use of simpler and cheaper antigen tests to confirm HCV infection in different clinical settings. We evaluated the sensitivity and specificity of antigen assays. This was compared with the reference-standard RNA assays. A subanalysis also assessed Architect core antigen test, which is the only commercially available antigen test on the market. In 24 datasets, evaluating HCV-antigen assays in 8136 samples, the percentage of HCV-antigen positive, HCV-RNA negative was 0.57%. The percentage HCV-antigen negative, HCV-RNA positive was 3.52%. There is strong evidence that antigen detection performs as well as RNA-based assays for HCV management. The use of antigen tests could improve access to HCV care in underresourced healthcare settings.

Hepatitis C virus core antigen assay: can we think beyond convention in resource limited settings?

Hepatitis C virus infects over 15 million patients from India and 2.86 million from Brazil. Detection of anti-hepatitis C virus antibodies has limited sensitivity during acute phase: the pre-seroconversion window period. Hepatitis C virus-RNA detection techniques are used to overcome this shortfall, but are costly and unavailable widely in developing countries. Estimation of hepatitis C virus core-antigen, a protein with highly conserved sequence, by enzyme-immunoassays is an economic and simpler alternative to RNA detection. This study was conducted in Delhi, involving 300 acute and chronic liver disease patients, tested for anti-hepatitis C virus 3rd-generation ELISA, hepatitis C virus core-antigen-ELISA and hepatitis C virus-RNA reverse transcription-polymerase chain reaction. Among the acute patients, hepatitis C virus core-antigen assay could identify 13 out of 14 pre-seroconversion window period cases and 6 out of 8 seroconverted cases, with a pre-seroconversion window period sensitivity of 92.9% and specificity of 100%. In hepatitis C virus core-antigen-positive cases, the viral load was in the range of 4900 to 1.46 × 10⁶ IU/mL, whereas in hepatitis C virus core-antigen-negative cases, the range of viral load was 100–4500 IU/mL. The cost of the hepatitis C virus core-antigen-ELISA was estimated around 3–4 times lesser than the in-house reverse transcription-polymerase chain reaction and 9–10 times lesser than the United States Food and Drug Administration approved reverse transcription-polymerase chain reaction. With a good sensitivity and specificity in the acute phase of infection, hepatitis C virus core-antigen-ELISA can thus be a useful alternative in the developing nations.

Core antigen tests for hepatitis C virus: a meta-analysis

Diagnosis and monitoring of hepatitis C virus (HCV) infection relies mainly on the detection of HCV antibodies and HCV RNA. HCV antibody test has a longer window period and is not applicable in the immunosuppressed population. Although HCV RNA test reduces the window period, it is still not widely recommended because of its high cost and requirement of specific equipment. HCV core antigen is another direct virological marker which has been investigated in recent years. HCV core antigen assay is as simple as the HCV antibodies assay and can detect HCV infection only 1 day delay compared to the HCV RNA assay. In order to evaluate the application of HCV core antigen test in HCV diagnosis and management, we performed this meta-analysis. Twenty five articles were finally included in meta-analysis. All statistical analyses were performed with MetaDisc 1.4 and Stata 11.0. The pooled sensitivity of HCV core antigen assay was 0.84 (95 % CI, 0.83-0.85), and the pooled specificity was 0.98 (95 % CI, 0.97-0.98). HCV core antigen assays may not displace HCV RNA assays to be a definitive diagnosis of HCV infection until now. Considering the higher sensitivity (0.926) and specificity (0.991) of subgroup, HCV-cAg detection is a promising method as a confirmatory test for HCV antibody positive, therapy-naive individuals. Explored by meta-regression and subgroup analysis, possible sources of heterogeneity of specificity was found, while the heterogeneity of sensitivity was still significant.

Evaluation of hepatitis C virus core antigen assays in detecting recombinant viral antigens of various genotypes

A single substitution within the hepatitis C virus core antigen sequence, A48T, which is observed in approximately 30% of individuals infected with genotype 2a virus, reduces the sensitivity of a commonly used chemiluminescence enzyme immunoassay. Quantitation of the antigen is improved by using a distinct anticore antibody with a different epitope.

Detection of hepatitis C virus core antigen for early diagnosis of hepatitis C virus infection in plasma donor in China

AIM: To evaluate the efficacy of a new hepatitis C virus (HCV) core antigen assay developed in China.

METHODS: After the determination of HCV infection, 49 serial samples were selected from 11 regular plasma donors in 5 different plasma stations. To compare the performance of HCV core antigen detection and HCV PCR, these samples were genotyped, and each specimen was analyzed by ELISA for the detection of HCV core antigen and by qualitative HCV PCR.

RESULTS: Among all of the sequential samples, the original 13 specimens were HCV RNA-negative, and 36 samples were HCV RNA-positive. Twenty-seven samples (75%) were HCV core antigen-positive from these HCV RNA-positive specimens. Conversely, 27 samples (93.1%) were found HCV RNA-positive in HCV core antigen-positive samples. Intervals between HCV RNA and HCV core antigen-positive, as well as between HCV core antigen-positive and HCV antibody-positive were 36.0 and 32.8 d, respectively.

CONCLUSION: This HCV core antigen assay, developed in China, is able to detect much of anti-HCV-negative, HCV RNA-positive preseroconversion window period (PWP) plasma donations.

[Use of combined detection of hepatitis C virus core antigen and antibodies to reduce the serological window-phase]

OBJECTIVES

In this study, we aimed at evaluating the performances of a combined assay for the detection of hepatitis C virus core antigen and antibodies and comparing this test with conventional third generation Elisa.

MATERIAL AND METHODS

Two hundred forty-one samples were included in this study and tested by Monolisa HCV Ag-Ab ULTRA, Biorad and compared to Monolisa Anti-HCV Plus. A comparative study was performed on a HCV seroconversion panel (Monolisa anti-HCV Plus, Biorad; Innotest HCV Ab IV, Innogenetics and Murex anti-HCV, Abbott). False positive samples were detected with western blot assay (INNO-LIA HCV Ab III, Innogenetics). Two anti-HCV negative haemodialysis patients with rise in ALT have been tested for RNA detection (Amplicor v2.0, Roche).

RESULTS

Results obtained with Biorad Ag-Ab were in agreement with third generation ELISA on HCV seroconversion panel. From anti-HCV negative patients, four samples were found low positive with HCV Ag-Ab. Two anti-HCV negative haemodialysis patients/HCV RNA positive were also negative with HCV Ag-Ab and 13 low positive samples with Biorad Ab were found negative with Ag-Ab.

CONCLUSION

The HCV Ag-Ab assay has a high specificity and sensitivity comparatively to conventional ELISA; but in our study we don't prove the reduction of the "serologic window" for detection of anti-HCV antibodies.

Evaluation of a total core antigen assay for the diagnosis of hepatitis C virus infection in hemodialysis patients

Hemodialysis patients are recognized as a group at high risk of infection with hepatitis C virus (HCV). Therefore, such a population should be screened routinely for the presence of HCV viremia. Since nucleic acid techniques remain expensive and largely unavailable in many laboratories in the developing world, the present study assesses the clinical usefulness of the HCV core antigen enzyme immunoassay for the diagnosis of HCV infection in dialysis patients. One hundred seventy-five dialysis patients were screened for the presence of anti-HCV antibodies and HCV RNA in the serum. One hundred twenty-eight serum samples were collected from the 76 patients who were anti-HCV antibody- and/or HCV RNA-positive. These were evaluated for total HCV core antigen. Of these samples, 55 had sufficient volume to be further tested to quantify HCV RNA by reverse transcription polymerase chain reaction (RT-PCR). Genotyping of the HCV strains showed that the majority belonged to genotype 1b (77%). The HCV core antigen assay showed a sensitivity and specificity of 84% and 89%, respectively. The use of core antigen assay has enabled the early detection of three patients who developed an acute hepatitis C infection during the period of study. A correlation study was undertaken between the quantitative values of viral load, expressed as pg/ml of HCV core antigen in serum, and viral RNA in UI/ml. A significant correlation was observed (Pearson's correlation coefficient: 0.552; P<0.001). In conclusion, detection of HCV core antigen in serum is an inexpensive, reliable, and highly specific assay that can be useful in most laboratory settings to diagnose HCV infection, and especially in laboratories where nucleic acid technologies are not yet available.

Simultaneous detection of hepatitis C virus (HCV) core antigen and anti-HCV antibodies improves the early detection of HCV infection

To evaluate whether a new enzyme immunoassay developed for the simultaneous detection of hepatitis C virus (HCV) core antigen (Ag) and anti-HCV antibodies (anti-HCV Ab) (Monolisa HCV Ag/Ab ULTRA; Bio-Rad) could improve the early detection of HCV infection, we compared its sensitivity to that of anti-HCV, HCV core Ag, and HCV RNA assays. The populations studied included 12 blood donor samples positive for HCV RNA and HCV core Ag but negative for anti-HCV antibodies and 23 hemodialysis patients who developed anti-HCV Ab (seroconversion) during the follow-up. From these 23 individuals, 83 samples sequentially collected prior to seroconversion and 108 samples collected after seroconversion were tested. Six of 12 blood donations were positive by the HCV Ag/Ab assay. In the hemodialysis cohort, the 24 HCV RNA-negative samples were negative by the HCV Ag/Ab assay and 23 of the 59 HCV RNA-positive samples (39%) were positive. The HCV Ag/Ab assay detected HCV infection on average 21.6 days before the most sensitive antibody assay. The HCV Ag/Ab assay did not detect HCV infection as early as the HCV RNA assay (mean delay, 30.3 days) or HCV Ag assay (mean delays, 27.9, and 16.3 days by the HCV core Ag quantification assay and the HCV Ag blood screening assay, respectively). This new assay provides a notable improvement for the early detection of HCV infection during the so-called window period compared with anti-HCV Ab assays and could be a useful alternative to HCV RNA detection or HCV core Ag assays for diagnosis or blood screening when nucleic acid technologies or HCV core Ag detection are not implemented.

Humoral immune response in acute hepatitis C virus infection

BACKGROUND

There is little information on the timing, magnitude, specificity, and clinical relevance of the antibody response to acute hepatitis C virus (HCV) infection. We investigated the specificity, titer, and neutralizing potential of antibody responses to acute infection by examining 12 injection drug users before, during, and after infection.

METHODS

Seroconversion was defined as incident detection of HCV-specific antibodies by using a commercially available enzyme-linked immuosorbent assay (ELISA). HCV protein-specific antibody responses were measured using recombinant antigens in an ELISA. For neutralization assays, plasma was incubated with human immunodeficiency virus (HIV)-HCV H77 or control HIV-murine leukemia virus (MLV) pseudotype virus and then allowed to infect Hep3B hepatoma cells.

RESULTS

The mean time to HCV seroconversion was 6 weeks after the onset of viremia. Antibody responses to nonstructural proteins were detected before responses to the structural proteins, and antibodies to both were primarily restricted to the immunoglobulin G1 (IgG1) subclass. The maximum median end point titers for antibody responses to structural and nonstructural proteins were 1 : 600 and 1 : 6400, respectively. Antibodies that neutralized a retroviral pseudotype bearing HCV 1a envelope glycoproteins were detected at seroconversion in only 1 subject and at 6-8 months after seroconversion in 3 subjects. The delayed appearance of neutralizing antibodies was consistent with the late development of antibodies specific for the viral envelope glycoproteins, which are believed to mediate virus neutralization.

CONCLUSION

The humoral immune response to acute HCV infection is of relatively low titer, is restricted primarily to the IgG1 subclass, and is delayed. A better understanding of why production of neutralizing antibody is delayed may improve efforts to prevent HCV infection.

Hepatitis B 1762T/1764A mutations, hepatitis C infection, and codon 249 p53 mutations in hepatocellular carcinomas from Thailand

Hepatocellular carcinoma is one of the leading causes of cancer death worldwide. The etiology of liver cancer is multifactorial, and infection with hepatitis B virus (HBV), whose pathogenesis is exacerbated by the acquisition of mutations that accelerate carcinogenesis, or hepatitis C virus (HCV) and dietary exposure to aflatoxin B(1) all contribute to elevating one's risk for this disease. In this study, we sought to determine the contributions of these agents by measuring the occurrence of an HBV 1762(T)/1764(A) double mutation, an aflatoxin-specific 249(G-->T) mutation of the p53 gene, and HCV in plasma of 34 HCC cases and 68 age- and gender-matched controls, and in 25 liver tumors from northern Thailand. In total, 14 cases, 5 controls, and 19 tumors had detectable levels of HBV DNA. All 14 cases, 2 controls (2.9%), and 17 tumors (89.5%) were positive for the HBV double mutation. Nine cases (26.5%), 10 controls (14.7%), and 6 tumors (24%) were positive for the p53 mutation. Five cases (14.7%), no controls, and 4 tumors (16%) had both mutations. The median age of HCC diagnosis in these 5 cases was 34 years versus 51 years for other cases. Five cases (14.7%) and 1 control (1.5%) were HCV enzyme immunoassay positive. Thus, specific HBV, HCV, and aflatoxin biomarkers reveal the complexity of risks contributing to HCC in northern Thailand and suggest further application of these biomarkers as intermediate end points in prevention, intervention trials, and etiologic investigations.

The role of core antigen detection in management of hepatitis C: a critical review

Several assays in research format and two commercial assays for the detection of hepatitis C virus (HCV) core protein or HCV core antigen have been developed in recent years. In order to elucidate the role and significance of HCV core antigen detection in the diagnosis and management of hepatitis C, we reviewed 56 studies published in peer-reviewed journals until September 2004. Evaluations in transfusion settings showed that the HCV core antigen assay detects HCV infection, similarly as nucleic acid techniques (NAT), between 40 and 50 days earlier than the current third generation HCV antibody screening assays. HCV core antigen levels closely track HCV RNA dynamics, and allow clinical monitoring of a patient's therapy, independently of HCV genotype, however, mainly in the samples with HCV RNA levels above 20,000 IU/ml. Considering the lower sensitivity of HCV core antigen detection in comparison to NAT, the HCV core antigen assay is not practical for the determination of the end of treatment response and sustained viral response, but could be useful for the determination of early viral response in the pegylated interferon-alpha and ribavirin treated patients infected with HCV genotype 1. The HCV core antigen detection is a viable tool for study of hepatitis C pathogenesis. The HCV core antigen can be used as a marker of HCV replication in anti-HCV positive individuals in the areas of the world that cannot afford NAT and/or in the settings that are not equipped or competent to perform HCV RNA testing. Because the manufacturer of HCV core antigen assays recently stopped an active marketing of these assays in several countries, it will, unfortunately and probably, never be possible to determine the actual potential and usefulness of HCV core antigen testing in the management of hepatitis C.

Detection of hepatitis C virus core antigen in blood donors using a new enzyme immunoassay

OBJECTIVES

The purpose of the study was to evaluate the presence of hepatitis C virus [HCV] core antigen (HCV core Ag) in blood donors at King Fahd Hospital of the University, Al-Khobar, using the new HCV core Ag assay, and to correlate this finding with anti-HCV antibodies detected in the same samples using the standard Abbott MEIA(microparticle enzyme immunoassay).

MATERIALS AND METHODS

A total of 898 samples from blood donors were analyzed using the new assay prototype designed to detect and quantify total HCV core Ag in serum (Ortho-Clinical Diagnostics). Positive results were confirmed by the neutralization assay. The results of the HCV core Ag assay were compared with the results of the standard Abbott MIEA which measures anti-HCV antibody.

RESULTS AND CONCLUSIONS

Out of the 898 samples tested, 18 samples were found to be positive by the HCV core Ag assay (2%). Out of these, 3 samples were confirmed positive by the neutralization protocol (0.33%). All the HCV core Ag positive samples were negative for anti-HCV antibodies (using MEIA by Abbott). These 3 donors may have been in the window period of HCV infection, or may be low responders for the HCV antigens, and are thus unable to mount detectable antibody level. The HCV core Ag assay is a potentially useful assay for screening blood donors, which will minimize the risk of using HCV positive blood from a patient in the window period of HCV infection.