Comparison of four methods for quantitative measurement of hepatitis B viral DNA

Real Time-PCR HBV-DNA Analysis: Significance and First Experience in Armed Forces

BACKGROUND

HBV DNA quantitation is used extensively world wide for the diagnosis and monitoring of treatment of Hepatitis B virus (HBV) infection. However, it has still to be popular in India. The aim of this study was to quantitate HBV - DNA by Real time - PCR method in Hepatitis B and in immuno-compromised patients, to compare the results with HBeAg detection and to monitor the response to therapy of chronic Hepatitis B patients to antivirals.

METHODS

Ninety one serum samples of Hepatitis group of patients (all HBsAg positive), 41 samples from immuno-compromised patients (all HBsAg negative) and 49 patients of Chronic Hepatitis B group (all HBsAg positive) were the subjects of this first ever study in Armed Forces. Twenty serum samples from healthy volunteers and non-hepatitis B patients served as negative controls. The amplification detection was carried out in a Rotor-Gene 2000-sequence detector.

RESULTS

Amongst Hepatitis B group, 33% (30/91) of the samples were positive for HBV-DNA and 26% (24/91) of samples were positive for HBeAg. In the immuno-compromised group of patients 14.6% (6/11) of samples were positive for HIV-DNA and 9.7% (4/41) were positive for HBeAg. Of the Chronic Hepatitis B patients on treatment, all (100%) were positive by HBV-DNA, whereas 29/49 (59.2%) were positive by HBeAg before treatment. After treatment with antivirals, 06/49 (12.2%) were positive by both tests and 11/49 (22.5%) were positive only by HBV-DNA. 32/49 (65.3%) patients became negative serologically after therapy.

CONCLUSION

HBeAg status did not necessarily reflect HBV-DNA level in the serum, as 10/91 (11%) in the Hepatitis B group, 2/41 (4.9%) in the immuno compromised group and 20/49 (40.8%) patients in the Chronic Hepatitis B group were positive for HBV-DNA but negative for HBeAg. HBV-DNA was not found to be positive amongst any of the negative controls. Real time - PCR is a sensitive and reproducible assay for HBV-DNA quantitation and may be started in Armed Forces referral centers in the near future.

Evaluation of the COBAS amplicor HBV monitor assay and comparison with the ultrasensitive HBV hybrid capture 2 assay for quantification of hepatitis B virus DNA

Performance characteristics of the COBAS Amplicor HBV Monitor test (Roche Diagnostics), which measures hepatitis B virus (HBV) DNA quantitatively, were evaluated and compared with the Ultrasensitive HBV Hybrid Capture 2 (HC2; Digene Corporation) assay. Linearity and within-run precision were assessed for both methods by using eight HBV DNA-positive samples serially diluted to obtain a range of <100 to 500,000 HBV DNA copies/ml and run in triplicate. Agreement between the methods was studied with 100 clinical samples. HC2 assay performance near the limit of detection was investigated through repeat testing of 149 samples with HC2 and testing of 37 samples with HC2 results of <4,700 HBV DNA copies/ml by Amplicor assay and a qualitative PCR assay. The linearity experiment for Amplicor had regression of observed values compared to expected values (y = 1.073x - 0.247; R(2) = 0.993, n = 32; for HC2, y = 0.855x + 0.759, R(2) = 0.729, n = 18). Within-run standard deviation of log HBV DNA copies/ml ranged from 0.003 to 0.348 (Amplicor) and 0.027 to 0.253 (HC2). Agreement assessed by Deming regression was poor [Amplicor = 1.197(HC2) - 0.961; R(2) = 0.799, standard error of the estimate (SEE) = 0.710, n = 94]. Near the lower limit of detection, 32 of 149 repeat HC2 results were <4,700 HBV DNA copies/ml. Of the 37 samples with HC2 results of <4,700 HBV DNA copies/ml, HBV DNA was not detected in 15 samples, while HBV DNA was detected by at least one PCR method in 12 samples. Amplicor is linear from 200 to 200,000 HBV DNA copies/ml with undiluted samples, and this range can be expanded through dilution. Inconsistent HC2 results near the limit of detection justify use of a grey zone.

Clinical evaluation of the COBAS Amplicor HBV monitor test for measuring serum HBV DNA and comparison with the Quantiplex branched DNA signal amplification assay in Taiwan

AIMS

To evaluate the performance characteristics and clinical usefulness of the COBAS Amplicor HBV monitor (COBAS-AM) test in Taiwan and to examine its correlation with the Quantiplex branched DNA signal amplification (bDNA) assay for measuring serum hepatitis B virus (HBV) DNA concentrations.

METHODS

HBV DNA was measured by the COBAS-AM test in 149 sera from chronic HBV infected patients that had previously been analysed by the bDNA assay.

RESULTS

The COBAS-AM test showed good reproducibility, with acceptable intra-assay and interassay coefficients of variation (1.6% and 0.9%, respectively) and good linearity (r2=0.98). The overall sensitivity of the COBAS-AM test was significantly higher than that of the bDNA assay (95.3% v 83.2%): 69.6% of samples with HBV DNA below the detection limit of the bDNA assay could be measured by the COBAS-AM test. There was a significant correlation between the results of the two assays (r=0.901; p<0.0001). On average, the results derived from the COBAS-AM test were 0.55 log lower than those of the bDNA assay. HBV DNA concentrations were significantly higher among HBV e antigen (HBeAg) positive patients than negative ones, and higher among patients with abnormal alanine aminotransferase (ALT) concentrations than those with normal ALT concentrations (p=0.0003).

CONCLUSIONS

The COBAS-AM assay, more sensitive in HBeAg negative samples than the bDNA assay, can effectively measure HBV DNA concentrations in Taiwanese patients. HBV DNA values measured by the COBAS-AM test and bDNA assay correlate significantly.

Quantitation of oligonucleotides by phosphodiesterase digestion followed by isotope dilution mass spectrometry: proof of concept

The importance of DNA as a regulatory analyte is well-known. Recent years have seen an increased interest in the quantitation of this analyte. Accurate quantitative measurements have been hampered by the lack of well-characterized standards and pure materials for this large-molecular-weight analyte. Outlined here is an approach for the accurate and reproducible quantitation of an oligonucleotide that is solely reliant on the availability of pure, well-characterized deoxynucleotides and not a sequence-specific pure DNA standard. The proposed procedure is intended to provide an accurate and definitive method for the quantitation of DNA for reference measurements as an improved alternative to the more conventional UV absorbance-based methods. For proof of concept, a gravimetrically prepared oligonucleotide solution was enzymatically digested to its constituent monomer-deoxynucleotide monophosphates (dNMPs), of which there are four different types. Qualitative mass spectrometry was used to confirm the 100% successful completion of the enzymatic digestion step. The dNMPs were then separated by liquid chromatography (LC) before being detected by electrospray ionization (ESI) mass spectrometry (MS). The method of quantitation was based on isotope dilution mass spectrometry (IDMS) analysis of the four different monomer units. The concentrations of the four dNMP residues were then summed to obtain the original concentration of the oligonucleotide. The concentrations determined by liquid chromatography/mass spectrometry (LC/MS) and also by liquid chromatography-tandem mass spectrometry (LC/MS/MS) differed by <2.5 and 1%, respectively, from the gravimetrically assigned value. These differences were well within the uncertainty of the gravimetrically assigned value. This highly accurate method, suitable for the definitive quantitation of oligonucleotides, should be ideal for characterizing primary calibration standards and certified reference materials that can then be used to underpin the more conventional quantitative techniques of UV and fluorescence spectroscopy.

Impact of HLA-compatibilities in patients undergoing liver transplantation for HBV-cirrhosis

Liver transplantation (OLT) for end-stage chronic hepatitis-B-virus (HBV) infection is frequently complicated by HBV recurrence. In the present study we investigated whether human leucocyte antigen (HLA)-matching influences the outcome after OLT. In a retrospective analysis we reviewed 84 recipients of liver transplants for end-stage HBV-cirrhosis and complete HLA-typing for outcome after OLT. Follow-up ranges from 1 to 110 months (median = 55.6 months). Immunosuppression consisted of Cyclosporin A (CsA)-based quadruple induction therapy or Tacrolimus-based induction protocols. Immunoprophylaxis with hepatitis B immunoglobulin was started at OLT and continued long-term. Actuarial 1- and 5-yr graft survival figures were 90.5 and 80.4%, respectively. Hepatitis-B recurrence was responsible for 15 of 20 (75%) graft failures. We observed a significantly improved graft survival in patients with more HLA-A, -B compatibilities (p = 0.02), whereas the degree of HLA-DR compatibilities did not influence the outcome. The occurrence of HBV-reinfection was significantly lower in HLA-A, -B matched grafts (p < 0.05). Additionally, graft survival was prolonged in patients with HBV-reinfection and 1 or 2 HLA-B compatibilities when compared with patients with HBV-reinfection and a complete HLA-B mismatch (p = 0.02). In conclusion, this retrospective analysis shows that more HLA-A, -B compatibilities seems to be associated with an improved graft survival in patients after OLT for end-stage HBV infection.

Comparison of commercial assays for the quantification of HBV DNA load in health care workers: calibration differences

Until recently, carriers of hepatitis B virus (HBV) were allowed to undertake exposure prone procedures providing their serum did not contain HBeAg. However, the recent description of hepatitis B transmission events occurring from HBV-infected health care workers who conduct exposure prone procedures demonstrated that the then current Department of Health guidelines needed to be revised. As part of a series of studies carried out to determine if viral load measurements are a more secure means of assessing the conduct of exposure prone procedures, the suitability of commercially available assays for HBV DNA detection and quantification were investigated. This study describes a comparative analysis on the performances of three assays each based on a different methodology. The assays included the QUANTIPLEX HBV DNA Assay (bDNA), (Chiron Diagnostics Ltd.), the AMPLICOR HBV Monitor Test, (Roche Diagnostics Systems) and the Digene Hybrid Capture System HBV DNA Assay (Digene Corporation). Calibration curves from experiments using the Eurohep ad and ay HBV DNA standard controls indicated a close correlation between the three assays over the dynamic ranges claimed by the manufacturers, although the Quantiplex assay did appear to be over-reporting. This became more apparent when testing patients undergoing anti-viral therapy where the Quantiplex assay consistently over-reported by 0.5 log(10) when compared with the Amplicor assay. The results of this study indicate that based on its dynamic range, the Amplicor HBV Monitor test is the most appropriate assay for the routine investigation of anti-HBe carriers, which will have lower levels of HBV DNA. The investigation also highlights the need for using accepted standard HBV DNA control sera. This will be essential when using an assay to establish whether health care workers who are hepatitis B carriers can be allowed to perform exposure prone procedures under the new guidelines of the UK Department of Health.

European proficiency testing program for molecular detection and quantitation of hepatitis B virus DNA

External quality control of hepatitis B virus (HBV) DNA detection remains an important issue. This study reports and compares the results obtained from two different proficiency panels for both the qualitative and quantitative assessment of HBV DNA. The panels were designed by the European Union Quality Control Concerted Action, prepared by Boston Biomedica, Inc., and distributed in May 1999 (panel 1) and February 2000 (panel 2). Each contained two negative samples and six positive samples with 10(3) to 10(7) copies/ml (panel 1) or 10(3) to 2 x 10(6) copies of HBV DNA per ml (panel 2). For panel 1, 42 laboratories submitted 20 qualitative (all in-house PCRs) and 37 quantitative (87% commercial assays) data sets. For panel 2, 51 laboratories submitted 25 qualitative (all in-house PCRs) and 47 quantitative (94% commercial assays) data sets. Five data sets (8.8%) in panel 1 and two data sets (2.8%) in panel 2 contained totals of six and two false-positives, respectively, corresponding to false-positive result rates of 5.3% for panel 1 and 1.4% for panel 2. The false-negative result rates of 10.5% for panel 1 and 17.4% for panel 2 were dependent on the detection levels of the assays employed as well as panel composition. In the qualitative analysis of all data sets, 47.4% (panel 1) and 51.4% (panel 2) had all samples correct. An adequate or better score (all correct or only the weak-positive sample missed) was obtained with 77.2% of the panel 1 samples and 68.1% of the panel 2 samples. In the quantitative analysis, 57.1% (panel 1) and 42.6% (panel 2) of the data sets achieved an adequate or better score (positive results within the acceptable range of the geometric mean +/- 0.5 log(10) of all positive results). These results demonstrate that while the qualitative performance of HBV detection has considerably improved compared to that of a previously published HBV proficiency study, the detection levels of many commercial quantitative assays are still too high to allow adequate quantitation of all relevant clinical samples.

Diagnosis and management of pre-core mutant chronic hepatitis B

Chronic hepatitis due to pre-core hepatitis B virus (HBV) mutants presents as hepatitis B e antigen (HBeAg)-negative chronic hepatitis B (CHB). HBeAg-negative CHB represents a late phase in the natural course of chronic HBV infection that develops after HBeAg loss and seroconversion to anti-HBe. It is usually associated with pre-core stop codon mutation at nucleotide 1896 (mainly selected in non-A HBV genotypes), but also with other pre-core changes or with mutations in the basic core promoter region (mainly in HBV genotype A). In chronic HBV infections, pre-core mutants can be detected both in patients with HBeAg-negative CHB and in inactive hepatitis B surface antigen (HBsAg) carriers. The diagnosis of HBeAg-negative CHB is based on HBsAg positivity, HBeAg negativity, and mainly on increased alanine aminotransferase (ALT) and serum HBV-DNA levels and exclusion of other causes of liver disease. The differential diagnosis between patients with CHB and inactive HBsAg carriers can be made only by close follow-up of aminotransferase activity and viraemia levels, although the cut-off level of serum HBV DNA has not been definitely determined. IgM anti-HBc levels have also been suggested as an index that increases the diagnostic accuracy for transient hepatitis flares, while liver biopsy confirms the diagnosis and evaluates the severity of the liver disease. Interferon-alpha (IFN-alpha) and lamivudine are the two drugs that have been tried, mainly in the management of HBeAg-negative CHB. A 12-month course of IFN-alpha achieves sustained biochemical remission in about 20% of patients, which has been associated with improvement in the long-term outcome of this subset. A 12-month course of lamivudine is rather ineffective, maintaining remission in less than 15% of patients after cessation of therapy. Long-term lamivudine is associated with progressively increasing rate of virological and subsequent biochemical breakthroughs due to YMDD mutants, with approximately 30% of patients remaining in remission in the third year of therapy. Several other antiviral agents are currently being evaluated in this setting with combined regimens being the most reasonable step for the near future.

Virological response to interferon therapy of chronic hepatitis B as measured by a highly sensitive assay

In the interferon (IFN) treatment of chronic hepatitis B, there is no accepted definition of virological response as measured by highly sensitive HBV DNA assays. In the present study of 98 patients given IFN (10 MU/day for 1 week, then 10 MU TIW for 11 weeks) with or without prednisolone priming, a virological response was identified as log HBV DNA/mL below 6.0 (by Amplicor Monitor, Roche) 6 months post-treatment. At this time, 92% (33/36) of the sustained responders (SR) still had detectable viraemia with log HBV DNA/mL at 4.30 +/- 0.15 (+/- SEM), as compared with 8.69 +/- 0.097 in nonsustained responders. Pretreatment viraemia below a threshold at 500 million copies/mL was associated with higher chance of response (P=0.023). Prednisolone enhanced the sustained response (53% vs. 30%, P=0.025), and in particular end-of-treatment response (ETR, 50% vs. 10%, P < 0.0001). ETR was predictive for SR (P < 0.0001), especially when log HBV DNA/mL was < 4.0 (PPV=92%). The potential value of differentiating the therapy of chronic hepatitis B on the basis of viraemia levels, as measured by highly sensitive assays, should be further investigated.

Limitations and improvements of the quantiplex branched-DNA assay in Hepatitis B virus-infected patients receiving lamivudine

The branched DNA (bDNA) assay for hepatitis B virus (Chiron Corporation Emerville, USA) was investigated by application to HBV-infected patients in Taiwan, where the B and C genotypes of hepatitis B virus are most prevalent. The study group included sera with hepatitis B surface antigen (HBsAg) and e antigen (HBeAg); Group 1 (n=70) without treatment; Group 2 (n=28) lamivudine treatment less than 3 months; Group 3 (n=73) lamivudine treatment 3-12 months; Group 4 (n=45) HBeAg-negative sera after 1 year treatment with lamivudine; control group (n=36) HBsAg-negative sera. Comparison of identical-sample results showed a significantly higher coefficient of variation for low-level HBV DNA (<100 MEq/ml) than for high-level (> or =100 MEq/ml), indicating increasing assay inaccuracy uncertainty as the sample HBV DNA concentration decreased. It is thus concluded that low-titered sera should receive special careful pipetting and processing. It was also found that using the relative luminescence of the negative control plus two standard deviations (S.D.) as a new cutoff could promote sensitivity (97.1-->97.1%, 89.3-->100%, 76.7-->84.9%, and 17.8-->22.2% in Groups 1-4, respectively) and specificity (94.4-->97.2%). In summary, the bDNA HBV assay showed only moderate assay performance for samples with low HBV DNA levels. This problem can be improved partially by choosing a new cutoff value based on the relative luminescence of the negative controls in the kit.

An international collaborative study to establish a World Health Organization international standard for hepatitis B virus DNA nucleic acid amplification techniques

BACKGROUND AND OBJECTIVES

Twenty-two laboratories from nine countries participated in an international collaborative study to establish a World Health Organization (WHO) international standard for hepatitis B virus (HBV) DNA nucleic acid amplification techniques (NAT).

MATERIALS AND METHODS

Three samples, AA, BB (both of which were lyophilized) and CC (which was a liquid preparation), were analysed using several different NAT assays. The mean HBV DNA content of each sample was determined from the study.

RESULTS

Despite the range of assays (commercial and in-house) used by participants, there was good agreement among the overall mean 'equivalents'/ml obtained by the different assays, except for one laboratory (laboratory 4). The variation in estimates of log10 'equivalents'/ml was 1.75-1.25 for the three samples if results from laboratory 4 were excluded. The mean log10 'equivalents'/ml for all laboratories were 6.42 for sample AA, 6.30 for sample BB and 5.03 for sample CC (exclusion of results from laboratory 4 made little difference). The difference in titres between the two lyophilized samples (AA and BB) was not statistically significant but the titre of the frozen sample (CC) was significantly lower. Material AA (code 97/746) was accepted as the first WHO international standard for HBV DNA NAT assays and assigned a potency of 10(6) international units (IU)/ml.

CONCLUSIONS

The titres (genome equivalents/ml) of three HBV preparations were determined by several laboratories using different NAT assays. This study enabled the establishment of an international standard, 97/746, for HBV DNA NAT assays.

Comparison of three different sensitive assays for hepatitis B virus DNA in monitoring of responses to antiviral therapy

The aim of our study was to compare the performances of two new hepatitis B virus (HBV) DNA assays, a cross-linking assay (NAXCOR) and a hybrid-capture amplification assay (Digene), versus the widely used branched-DNA (bDNA) assay (Chiron) in the monitoring of HBV DNA levels during antiviral treatment. Serial serum samples from 12 chronically HBV infected patients undergoing a phase II trial of an antiviral drug, 2',3'-dideoxy-5-fluoro-3'-thiacytidine (FTC), were studied. A total of 96 serum samples were tested for HBV DNA using the cross-linking, hybrid-capture amplification, and bDNA assays. In the comparison of the cross-linking and bDNA assays, concordant results were found in 77 (80.3%) samples, no significant difference was found between the median log(10) HBV DNA levels (6.66 versus 7. 17 meq/ml), and the results of the two assays were closely correlated (r = 0.95). In the comparison of the hybrid-capture amplification and bDNA assays, concordant results were found in 79 (82.3%) samples, no significant difference was found between the median log(10) HBV DNA levels (6.98 versus 6.99 meq/ml), and the results of the two assays were closely correlated (r = 0.99). Six (6. 3%) samples by the cross-linking assay and 10 (10.4%) samples by the bDNA assay required retesting because of unacceptably high within-run coefficients of variance. No sample required retesting in the hybrid-capture amplification assay according to the internal validation. In conclusion, the cross-linking and hybrid-capture amplification assays were as sensitive as the bDNA assay for HBV DNA detection and can be recommended for monitoring of HBV DNA levels during antiviral treatment.

Evaluation of an enzyme-linked immunosorbent assay for detection and quantification of hepatitis B virus PreS1 envelope antigen in serum samples: comparison with two commercial assays for monitoring hepatitis B virus DNA

An in-house sensitive and easy-to-use solid-phase enzyme-linked immunoassay (ELISA) was adapted for the detection and quantification of hepatitis B virus (HBV) PreS1 envelope antigen in serum, and compared with the HBV DNA Hybrid Capturetrade mark system from Murex and the polymerase chain reaction (PCR) Amplicortrade mark HBV Monitor assay from Roche. Twenty-five patients with chronic hepatitis B after liver transplantation were included in this study. The sensitivity of our ELISA was found to be 50 pg of HBsAg/PreS1Ag ml-1. The linearity was between 0.1 and 100 ng ml-1. Intra-assay reproducibility was obtained with a standard deviation of <1%. No correlation between the presence of serum PreS1 antigen and viral DNA detected by direct hybridization (Murex) was observed. In contrast, there was a significant 96% correspondence in the presence of PreS1 antigen and viral DNA detected and quantified by the PCR assay (Roche). In conclusion, the most important and reliable markers for monitoring residual HBV replication in serum were HBV DNA by the PCR assay, and virus envelope PreS1Ag by our in-house ELISA. Thus, PreS1Ag disappearance in serum could be used for evaluating the efficacy of antiviral therapies.

Development of a quantitative real-time detection assay for hepatitis B virus DNA and comparison with two commercial assays

A highly reproducible and sensitive real-time detection assay based on TaqMan technology was developed for the detection of hepatitis B virus (HBV) DNA and compared with two commercially available assays. The assay was validated with the Viral Quality Control panel, which also includes EUROHEP HBV DNA standards. This real-time PCR detection system had a dynamic range of 373 to 10(10) genome copies per ml and showed an excellent correlation with both the commercial HBV Digene Hybrid Capture II microplate assay (Digene Diagnostics) and the HBV MONITOR assay (Roche Diagnostics). To demonstrate its clinical utility, four chronically HBV-infected patients treated with lamuvidine were monitored using the three different assays. From the results we concluded that this assay is an excellent alternative for monitoring of HBV-infected patients in routine diagnostics and clinical practice, enabling the analysis of a large dynamic range of HBV DNA in a single, undiluted sample.

Predictive factors for response to lamivudine in chronic hepatitis B

BACKGROUND

Lamivudine has been shown to be an efficient drug for chronic hepatitis B (CHB) treatment.

AIM

To investigate predictive factors of response, using a quantitative method with high sensitivity.

METHODS

We carried out a prospective trial of lamivudine in 35 patients with CHB and evidence for viral replication, regardless to their HBeAg status. Lamivudine was given for 12 months at 300 mg daily and 150 mg thereafter. Response was considered when DNA was undetectable by PCR after 6 months of treatment. Viral replication was monitored by end-point dilution PCR. Mutation associated with resistance to lamivudine was detected by DNA sequencing in non-responder patients.

RESULTS

Response was observed in 23/35 patients (65.7%) but only in 5/15 (33.3%) HBeAg positive patients. Only three pre-treatment variables were associated to low response: HBeAg (p = 0.006), high viral load (DNA-VHB > 3 x 10(6) copies/ml) (p = 0.004) and liver HBcAg (p = 0. 0028). YMDD mutations were detected in 7/11 non-responder patients.

CONCLUSIONS

HBeAg positive patients with high viral load show a high risk for developing drug resistance. On the other hand, HBeAg negative patients show a good response to lamivudine even with high viremia.

A multicenter study evaluation of the digene hybrid capture II signal amplification technique for detection of hepatitis B virus DNA in serum samples and testing of EUROHEP standards

We have evaluated the new Digene Hybrid Capture II HBV DNA Test (HCII HBV), which is a 96-well microtiter plate-based signal amplification assay. This test uses hybrid capture technology that specifically detects RNA-DNA hybrids. HCII HBV is able to quantify hepatitis B virus (HBV) DNA at between 1.4 x 10(5) and 1.7 x 10(9) HBV copies per ml in a standard format. By using a modified sample preparation method, which allows the input of 30-fold more serum for an ultrasensitive format, the sensitivity of the assay can be increased reproducibly to approximately 8,000 copies of HBV per ml. By using a combination of these two formats, the assay can quantify over a total range of 6 logs. In our multicenter evaluation study, the mean laboratory-to-laboratory coefficients of variation were 22, 7, and 12% at the three sites, respectively, with a combined specificity of 98.4%. The linearities of both the standard test and the ultrasensitive test were excellent, with Spearman correlation coefficients of 0.997 and 0.999, respectively. Furthermore, the intra-assay reproducibility for the standard assay gave coefficients of variation of from 13 to 33, 9 to 21, and 3 to 8% at the three sites, respectively. HCII HBV was shown to be genotype independent when the EUROHEP standards for genotypes A and D were used. This assay allows the accurate measurement of HBV DNA levels in serum and can be clinically used for the monitoring of responses to antiviral agents for patients chronically infected with HBV.

Persistence of viral replication after anti-HBe seroconversion during antiviral therapy for chronic hepatitis B

BACKGROUND/AIMS

Hepatitis B virus genome mutants may be selected during the immune-mediated clearance of infection or during long-term nucleoside analog administration and may escape both antiviral pressures. The pattern of anti-HBe seroconversion was analyzed in patients receiving new nucleoside analogs, lamivudine or famciclovir, in comparison with patients treated with interferon alpha.

METHODS

Eighteen consecutive patients who seroconverted to anti-HBe were included in the study. Serial serum samples were studied with the quantitative determination of HBV DNA by the branched DNA assay (Chiron) and by a quantitative PCR assay (Roche diagnostics), determination of pre-S1 Ag, the genetic analysis of the viral genome with the determination of pre-core promoter or pre-core region mutations with a line probe assay (Innogenetics) and, in selected samples of polymerase gene mutations.

RESULTS

The quantitative PCR assay was found to be more sensitive than the bDNA assay, allowing a 25-log decrease in viral DNA levels to be demonstrated after anti-HBe seroconversion. Viral persistence after anti-HBe seroconversion induced by interferon, lamivudine or famciclovir, was often associated with circulating HBV genomes harboring mutations in the precore promoter. The clinical significance of these findings was demonstrated by the observation of reversion to HBeAg in two patients treated with interferon and one with lamivudine.

CONCLUSION

Persistence of significant levels of viremia that are not detected by the branched DNA assay may be observed after anti-HBe seroconversion. A precise monitoring of viremia levels with more sensitive assays and HBV mutant strains is warranted in patients undergoing antiviral therapy.

Molecular methods of measurement of hepatitis B virus, hepatitis C virus, and human immunodeficiency virus infection: implications for occupational health practice

Over the past decade, several molecular techniques for the detection of human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) have been developed that have implications for occupational health practice. This review describes the techniques used for qualitative and quantitative detection of the viral genome, and briefly explains nucleic acid sequencing and analysis of phylogenetic trees. The review also discusses the current and potential uses of these techniques in investigations of transmission of bloodborne viruses by patient to worker and worker to patient, in the management of occupational exposure to blood, in research, and in the development of guidance and policy on infected healthcare workers who perform procedures prone to exposure.

Comparison of the second-generation digene hybrid capture assay with the branched-DNA assay for measurement of hepatitis B virus DNA in serum

The optimal hepatitis B virus (HBV) DNA quantitative assay for clinical use remains to be determined. We examined the sensitivity, linearity, and variability of a novel second-generation antibody capture solution hybridization assay, the Digene Hybrid Capture II assay (HCII), and compared it with another widely used solution hybridization assay, the branched-DNA (bDNA) assay (Quantiplex; Chiron Corp.). Our results showed similar and satisfactory assay linearity values, as well as interassay and intra-assay variability values, for both HCII and bDNA assays across different ranges of HBV DNA. Ninety-one percent of 102 serum samples from hepatitis B surface antigen-positive patients showed concordant results with the two assays. The HCII assay was more sensitive than the bDNA assay by 1 dilution, with the lowest reading being 0.9 pg/ml (3.8 pg/ml by bDNA assay). The HBV DNA seropositivity rates for the 102 samples were 58, 67, and 97% by bDNA, HCII, and nested PCR, respectively. While the relationship between results obtained with the bDNA assay and those with the HCII assay was nonlinear, with the bDNA assay yielding values 2.83 +/- 0.92-fold higher than those of the HCII assay, especially at high HBV DNA levels, a linear relationship was observed between the two sets of data after logarithmic conversion. The formula for interassay conversion of results was derived as follows: HBV DNA by HCII (picograms per milliliter) = 3.19 x [HBV DNA by bDNA (megaequivalents per milliliter)](0.866). The HCII assay was technically less complex and required a shorter assay time (4 h) than the bDNA assay (24 h). We conclude that the HCII assay compares favorably with the bDNA assay and offers the additional advantages of increased sensitivity and shorter assay time. The increased sensitivity should be particularly useful in monitoring the efficacy of antiviral therapies and detecting the emergence of drug-resistant HBV mutants.

Interferon alfa for chronic hepatitis B infection: increased efficacy of prolonged treatment. The European Concerted Action on Viral Hepatitis (EUROHEP)

Interferon alfa (IFN-alpha) is the primary treatment for chronic hepatitis B. The standard duration of IFN-alpha therapy is considered 16 weeks; however, the optimal treatment length is still poorly defined. We evaluated the efficacy and acceptability of prolonged IFN-alpha treatment in patients with chronic hepatitis B. To investigate whether treatment prolongation could enhance the rate of hepatitis B e antigen (HBeAg) seroconversion, we conducted a prospective, controlled, multicenter trial in which all patients were treated with a standard regimen of 10 million units IFN-alpha 3 times per week over 16 weeks. Patients who were still HBeAg-positive after 16 weeks of therapy were randomized to prolongation of the identical regimen up to 32 weeks (prolonged therapy) or discontinuation of treatment (standard therapy). Among the 162 patients who entered the study, 27 (17%) were HBeAg-negative after the first 16 weeks of treatment, and 118 were randomized to standard or prolonged therapy. After randomization, a response (HBeAg seroconversion and sustained hepatitis B virus [HBV]-DNA negativity) was observed in 7 of the 57 (12%) patients assigned to standard therapy versus 17 of the 61 (28%) patients assigned to prolonged therapy (P =.04). A low level of viral replication after 16 weeks of treatment, as indicated by serum HBV-DNA values under 10 pg/mL, was found to be the only independent predictor of response (52% vs. 0%; P <.001) during prolonged therapy. The prolonged IFN-alpha schedule was well tolerated in the large majority of patients. In chronic hepatitis B, prolongation of IFN-alpha therapy up to 32 weeks is superior to a standard course of 16 weeks. Those patients who exhibit a low level of viral replication at the end of the standard regimen benefit most from prolonged treatment.

Effect of multiple freeze-thaw cycles on hepatitis B virus DNA and hepatitis C virus RNA quantification as measured with branched-DNA technology

Quantification of hepatitis B virus (HBV) DNA and hepatitis C virus (HCV) RNA often is performed in specimens that have been frozen and thawed more than once. To ensure optimal therapeutic and prognostic value, it is important to establish whether viral load measurements are affected by repeated freeze-thaw (FT) cycles. We therefore evaluated the effect of multiple FT cycles on HBV DNA and HCV RNA quantification by testing serum specimens subjected to one (baseline), two, four, and eight FT cycles with the appropriate Chiron Quantiplex assay. Linear regression analysis showed minor increases of 1.7% per FT cycle for both HBV DNA and HCV RNA. The rise in HCV RNA levels was more pronounced among low-concentration samples, since further analysis revealed an increase of 3.2% per FT cycle among samples with 0.2 to 3.86 Meq of HCV RNA per ml. Given that the coefficient of variation for the Quantiplex assays is generally 10 to 15%, the minor increases in HBV DNA and HCV RNA levels with progressive FT cycles for the specimens tested were recognized only because analysis of variance revealed a statistically significant trend (P < 0.05). Due to the minor statistical trend, the clinical impact for individual patient specimens is likely to be limited, but it may deserve further study. In conclusion, the concentration of HBV DNA and HCV RNA in serum specimens subjected to up to eight short-term FT cycles was stable.

Comparison of two methods for quantification of hepatitis B viral DNA

BACKGROUND

Quantitation of serum hepatitis B virus (HBV) DNA has proven useful in assisting with patient management and treatment and several commercially available assays have been developed to quantify serum HBV-DNA levels.

METHODS

The performance of the cross-linking assay and the branched-DNA signal amplification (bDNA) assay for the quantitative measurement of HBV-DNA was studied in 99 hepatitis B surface antigen-positive and viraemic patients.

RESULTS

Of these samples, 82 (83%) were positive for HBV-DNA by both assays and four (4%) were below the cut-off for both assays. Of the remaining 13 samples, 10 contained measurable levels of HBV-DNA by the cross-linking assay alone and three other samples contained measurable levels of HBV-DNA by the bDNA assay alone. The sensitivity gain of the cross-linking assay relative to bDNA assay in this study population was 10/92 (11%). In addition, a linear regression analysis showed that the HBV-DNA levels obtained from both assays was significantly correlated (gamma=0.974, P< 0.0001).

CONCLUSIONS

These findings suggest that the recently developed cross-linking assay is more sensitive than the bDNA assay for the quantitative determination of HBV-DNA.

Branched DNA signal amplification for direct quantitation of nucleic acid sequences in clinical specimens

In this chapter I have reviewed the development of bDNA as a method for quantitation of nucleic acid targets and the application of this technology to the study of infectious diseases and cell biology. The ability to quantify viral nucleic acids in clinical specimens has led to a better understanding of the pathogenesis of chronic viral infections such as HIV-1, HCV, and HBV. The information provided by these methods can also be important in the management of patients with these infections. The prognostic value of a single baseline HIV-1 RNA level rivals that surgical staging procedures for cancer, which are among the most powerfully predictive tests in medicine (Mellors et al., 1996). These methods have been used to assess rapidly the effects of antiviral therapy, which has both expedited the development of antiviral drugs and improved the management of patients with HIV-1 and HCV infections. bDNA has several characteristics that distinguish it from the quantitative target amplification systems, including better tolerance of target sequence variability, more direct measurement of target, simpler sample preparation, and less sample-to-sample variation. However, the first- and second-generation bDNA assays lacked sensitivity compared with the target amplifications systems. The changes incorporated into the third-generation assays have effectively increased the signal-to-noise ratio to such a high level that the analytical sensitivity of system 8 bDNA approaches that of PCR. In theory, bDNA can be made even more sensitive by increasing both the sample volume and the signal-to-noise ratio. Nonspecific hybridization can be further reduced by finding more effective blockers for the solid phase or by redesigning the amplifier molecule or the solid phase itself. The increased sensitivity may create new applications for the technology in filter and in situ hybridization assays.

Quantitative detection of hepatitis B virus DNA in two international reference plasma preparations. Eurohep Pathobiology Group

Quantitative detection of hepatitis B virus (HBV) in serum or plasma is of significance for monitoring of therapy and establishment of the prognosis of the disease, as well as for infectivity assessment and quality control of the diagnosis. Unfortunately, various commercially available test kits for HBV DNA yielded conflicting quantitative results, with differences of up to a factor of 120. The Eurohep Pathobiology Group has established two reference samples of plasma from HBV carriers and determined as accurately as possible the number of HBV DNA molecules in these samples. Plasma donations from two single highly viremic carriers of HBV genotype A (HBV surface antigen subtype adw2) and genotype D (ayw2/3), respectively, were collected, and coded dilutions of these samples were analyzed by members of the Eurohep Pathobiology Group. Quantitative results from the seven laboratories reporting consistent results were initially divergent. Limiting dilution and nested PCR assays suffered from incomplete DNA extraction. Hybridization assays used inaccurately quantitated cloned DNA as a reference. Two hybridization assays could not be calibrated directly with cloned HBV DNA, because virion-derived DNA reacted much less efficiently. After identification and elimination of these problems, limiting-dilution assays from three laboratories and hybridization assays from two producers generated consistent and concordant results: 2.7 x 10(9) HBV DNA molecules/ml (range, 2.1 x 10(9) to 3.4 x 10(9) HBV DNA molecules/ml) in the plasma from the carrier of genotype A and 2.6 x 10(9) HBV DNA molecules/ml (range, 2.1 x 10(9) to 3.0 x 10(9) HBV DNA molecules/ml in the plasma from the carrier of genotype D. The two Eurohep reference plasma samples have already been used for the standardization of test kits and in quality control trials, and the plasma from the carrier of genotype A will probably be the basis of a World Health Organization reference sample.

Nucleic acid-based cross-linking assay for detection and quantification of hepatitis B virus DNA

A nucleic acid photo-cross-linking technology was used to develop a direct assay for the quantification of hepatitis B virus (HBV) DNA levels in serum. Cross-linker-modified DNA probes complementary to the viral genomes of the major HBV subtypes were synthesized and used in an assay that could be completed in less than 6 h. The quantification range of the assay, as determined by testing serial dilutions of Eurohep HBV reference standards and cloned HBV DNA, was 5 x 10(5) to 3 x 10(9) molecules of HBV DNA/ml of serum. Within-run and between-run coefficients of variation (CVs) for the assay were 4. 3 and 4.0%, respectively. The assay was used to determine HBV DNA levels in 302 serum samples, and the results were compared to those obtained after testing the same samples with the Chiron branched-DNA (bDNA) assay for HBV DNA. Of the samples tested, 218 were positive for HBV DNA by both assays and 72 gave results below the cutoff for both assays. Of the remaining 12 samples, 10 were positive for HBV DNA by the cross-linking assay only; the 2 other samples were positive by the bDNA assay only. Twenty-eight samples had to be retested by the bDNA assay (CV, >20% between the results obtained from the testing of each sample in duplicate), whereas only three samples required retesting by the cross-linking assay. The correlation between the HBV DNA levels, as measured by the two tests, was very high (r = 0.902; P = 0.01). We conclude that the cross-linking assay is a sensitive and reproducible method for the detection and quantification of HBV DNA levels in serum.

Multi-measurement method comparison of three commercial hepatitis B virus DNA quantification assays

Serum specimens (327) from patients with chronic hepatitis B were evaluated for hepatitis B virus (HBV) DNA using three commercial assays--Chiron Quantiplex (CA), Digene Hybrid Capture (DA) and Abbott HBV DNA assay (AA). The HBV DNA values obtained following evaluation were used to compare the linearity, responsiveness and precision of each assay and to determine the conversion between the three different assay values. The comparison was accomplished using a new statistical approach termed the multi-measurement method (MMM). MMM is a minimal bias, non-linear regression technique that allows simultaneous multiassay performance evaluation as well as assay value interconversion. MMM analysis demonstrated that the CA was more sensitive and responsive than either the DA or the AA. Both the CA and DA were more precise than the AA. Validation of the MMM results was performed using two additional data sets of 551 and 100 specimens, respectively. MMM is a novel statistical tool that has a broad application for the generation of statistically normalized laboratory data and for interassay standardization.

Clinical evaluation of the branched DNA assay for hepatitis B virus DNA detection in patients with chronic hepatitis B lacking hepatitis B e antigen and treated with interferon-alpha

The aim of this study was to evaluate the Chiron branched DNA (bDNA) assay for detection of serum hepatitis B virus (HBV) DNA in patients with chronic hepatitis B lacking hepatitis B e antigen (HBeAg) and undergoing interferon (IFN) therapy. Results obtained with the bDNA assay were compared with those obtained using the Abbott liquid hybridization (LH) assay and the polymerase chain reaction (PCR). Serial samples (274) from 34 patients were analysed. Analysis of variance results indicated that bDNA values were more significantly correlated than LH values with both PCR positive/negative results (probability of artifact (Prob > F) = 0.7 and 0.09 for LH and bDNA assays, respectively) and presence/absence of precore mutations (Prob > F = 0.21 and 0.001 for LH and bDNA assays, respectively). Both bDNA and LH results correlated highly with alanine aminotransferase (ALT) values (both had Prob > F values of 0.0) while PCR was not correlated with ALT (Prob > F = 0.05). In 26 evaluable patients, a model based on a generalized Knodell score was used to predict response to IFN therapy, as defined by normalization of ALT values during therapy. This model discriminated well between non-responders and responders. The bDNA results correlated well with the generalized Knodell score, while the LH results did not (Prob > F = 0.04 and 0.19 for the bDNA and LH assays, respectively). In conclusion, the bDNA assay appears to be useful for quantification of HBV DNA levels in HBeAg-negative chronic hepatitis as it correlates with biochemical and histological indications of disease severity as well as with response to IFN therapy.

Clinical evaluation and applications of the Amplicor HBV Monitor test, a quantitative HBV DNA PCR assay

Viral load has emerged recently as a reliable marker of disease progression and therapeutic efficacy in chronic infections, including AIDS and hepatitis C. The clinical management of type B hepatitis could also be improved by monitoring viremia levels in patients with chronic liver disease undergoing anti-viral treatment. To address this question we evaluated the performance of a newly developed, quantitative PCR assay (Amplicor HBV Monitor test, Roche Diagnostic Systems) in the assessment of viremia changes over time in a group of 45 patients with chronic active hepatitis (CAH) who received interferon treatment. Of the 45 patients, 14 were HBsAg and anti-HBeAg positive and 31 HBsAg, HBeAg positive. Follow-up extended up to 24 months. An average of ten samples per patient were analyzed for levels of ALT, IgM anti-HBc (Abbott Laboratories), HBV DNA by in-house dot-blot hybridization and hybridization-capture assays (HBV-DNA hybrid capture kit, Murex Diagnostics) and by Amplicor HBV Monitor. A sustained biochemical response was observed at the end of treatment in 12 HBeAg-positive and in seven anti-HBeAg positive patients. This was accompanied by the disappearance of HBeAg and of HBV DNA (hybridization assays) in all cases and by the clearance of IgM anti-HBc in 70% of the cases. Viremia (quantitative PCR assay) became undetectable only in 25-30% of cases and was associated with the loss of HBsAg. A good correlation was observed between the time course of IgM anti-HBc, quantitative PCR and dot-blot hybridization although the latter missed 33% of viremic samples. Together, these results indicate that the Amplicor HBV Monitor test is a robust and standardized assay for quantifying HBV viremia levels in the range from 10(2) to 10(7) copies/ml. Compared to other current markers, viral load may provide additional clinical information by predicting long term virologic response and HBsAg clearance in patients with normal ALT at the end of interferon therapy.

The clinical utility of viral quantitation using molecular methods

BACKGROUND

The quantitation of viral nucleic acids in biological fluids has become increasingly desirable over the past several years. To this end, a number of quantitative molecular procedures have been developed.

OBJECTIVES

The objective was to review the current literature on the molecular techniques used in the quantitation of viral nucleic acids and to assess the appropriateness of these methods for clinical use.

RESULTS

Assays involving both target and signal amplification are now available for the accurate and precise quantitation of viral burden in infected patients. These methods include quantitative polymerase chain reaction (PCR), branched chain signal amplification (bDNA), nucleic acid sequence-based amplification (NASBA) and the SHARP signal and hybrid capture systems. Our understanding of the natural history and pathogenesis of viruses such as the human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), cytomegalovirus (CMV) and Epstein-Barr virus (EBV) may be greatly facilitated by accurate determinations of viral and infected cell burden. Quantitation of viral load in infected individuals may also be useful to assess disease progression, monitor the efficacy of therapy and to predict treatment failure and the emergence of drug-resistant viruses.

CONCLUSION

Precise, accurate and reproducible quantitation of viral load is now feasible. Molecular assays for viral quantitation should have a considerable impact on medical research and clinical care.

Assessment of hepatitis B virus DNA stability in serum by the Chiron Quantiplex branched-DNA assay

Quantification of hepatitis B virus (HBV) DNA in serum is used to establish eligibility for treatment and to monitor therapeutic response. With the trend toward centralized testing, defining the conditions that preserve sample integrity is of paramount importance. We therefore evaluated the stability of HBV DNA in 26 previously frozen (PF) and 5 fresh, never previously frozen serum specimens. PF specimens, covering a 3-log10 HBV DNA dynamic range, were thawed and stored at -70, 4, 23, 37, and 45 degrees C (+/-1.5 degrees C) for 0, 24, 72, and 120 h (+/-2 h) and were refrozen at -70 degrees C prior to testing. Five fresh specimens were split into two groups. Both group FG1 and group FG2 specimens were handled as described above; however, group FG1 specimens were subsequently maintained at 4 degrees C and were never frozen prior to testing. Linear regression analysis of PF specimens demonstrated no significant HBV DNA degradation at < or =4 degrees C over 5 days; however, HBV DNA levels decreased by 1.8, 3.4, and 20% per day at 23, 37, and 45 degrees C, respectively. Three independent statistical methods confirmed that the probability of specimen failure, defined as a loss of 20% or more of HBV DNA and/or coagulation of serum, was lowest at < or =4 degrees C and increased with temperature. Because only 10 to 20% of individual patient specimens demonstrated losses of HBV DNA of > or =20% at 23 or 37 degrees C, sufficient numbers of serum specimens must be evaluated to determine overall statistical trends. In conclusion, HBV DNA integrity in separated serum specimens is preserved for at least 5 days when the specimens are stored at -70 or 4 degrees C.

Diagnostic tools in the evaluation of patients with viral hepatitis undergoing liver transplantation

Familiarity with the diagnostic parameters of viral hepatitis is imperative in the liver transplantation arena. Chronic viral hepatitis B and C are among the most common categories of end-stage liver disease. The preoperative diagnosis, determination of recurrent infection, and the assessment of antiviral therapeutic efficacy are dependent on appropriate virological testing. Furthermore, liver transplant personnel are at a high risk for parenterally transmitted viral hepatitis infection. Knowledge and understanding of the serological patterns of acute and chronic viral hepatitis, as well as recognition of the immune status for one or more of these viruses, will facilitate prevention and treatment of viral hepatitis for these health care providers.