Real time TaqMan PCR detection and quantitation of HBV genotypes A-G with the use of an internal quantitation standard

Identifying the Genotypes of Hepatitis B Virus (HBV) with DNA Origami Label

The hepatitis B virus (HBV) genotyping may profoundly affect the accurate diagnosis and antiviral treatment of viral hepatitis. Existing genotyping methods such as serological, immunological, or molecular testing are still suffered from substandard specificity and low sensitivity in laboratory or clinical application. In a previous study, a set of high-efficiency hybridizable DNA origami-based shape ID probes to target the templates through which genetic variation could be determined in an ultrahigh resolution of atomic force microscopy (AFM) nanomechanical imaging are established. Here, as a further confirmatory research to explore the sensitivity and applicability of this assay, differentially predesigned DNA origami shape ID probes are also developed for precisely HBV genotyping. Through the specific identification of visualized DNA origami nanostructure with clinical HBV DNA samples, the genetic variation information of genotypes can be directly identified under AFM. As a proof-of-concept, five genotype B and six genotype C are detected in 11 HBV-infected patients' blood DNA samples of Han Chinese population in the single-blinded test. The AFM image-based DNA origami shape ID genotyping approach shows high specificity and sensitivity, which could be promising for virus infection diagnosis and precision medicine in the future.

Evaluation of the Aptima HBV Quant assay vs. the COBAS TaqMan HBV test using the high pure system for the quantitation of HBV DNA in plasma and serum samples

Background:

Proper management of patients with chronic hepatitis B virus (HBV) infection requires monitoring of plasma or serum HBV DNA levels using a highly sensitive nucleic acid amplification test. Because commercially available assays differ in performance, we compared herein the performance of the Hologic Aptima HBV Quant assay (Aptima) to that of the Roche Cobas TaqMan HBV test for use with the high pure system (HPS/CTM).

Methods:

Assay performance was assessed using HBV reference panels as well as plasma and serum samples from chronically HBV-infected patients. Method correlation, analytical sensitivity, precision/reproducibility, linearity, bias and influence of genotype were evaluated. Data analysis was performed using linear regression, Deming correlation analysis and Bland-Altman analysis.

Results:

Agreement between the assays for the two reference panels was good, with a difference in assay values vs. target <0.5 log. Qualitative assay results for 159 clinical samples showed good concordance (88.1%; κ=0.75; 95% confidence interval: 0.651–0.845). For the 106 samples quantitated by both assays, viral load results were highly correlated (R=0.92) and differed on average by 0.09 log, with 95.3% of the samples being within the 95% limit of agreement of the assays. Linearity for viral loads 1–7 log was excellent for both assays (R2>0.98). The two assays had similar bias and precision across the different genotypes tested at low viral loads (25–1000 IU/mL).

Conclusions:

Aptima has a performance comparable with that of HPS/CTM, making it suitable for use for HBV infection monitoring. Aptima runs on a fully automated platform (the Panther system) and therefore offers a significantly improved workflow compared with HPS/CTM.

Real-time TaqMan assay for myxovirus resistance protein (MxA) mRNA: a robust marker of interferon beta bioactivity in patients with multiple sclerosis

For many patients suffering from MS, interferon beta (IFNβ) is an effective therapeutic option; however, some patients who receive long-term IFNβ therapy for relapsing-remitting MS (RRMS) develop neutralizing antibodies (NAbs) that affect IFNβ efficacy. It is therefore important to evaluate patients' therapeutic response to IFNβ over time. Myxovirus resistance protein A (MxA), a surrogate marker of individual immunologic response to IFNβ, may be a useful tool for assessing IFNβ immunogenicity. The real-time TaqMan assay for MxA messenger RNA (mRNA) has several distinct advantages, including the ability to amplify and complete quantitative analyses in one step, a high degree of quality control and prior experience and confidence in the field of quantitative viral diagnostics. The real-time TaqMan assay for MxA mRNA can be incorporated as a component of IFNβ therapy to evaluate patients during the course of treatment. Multiple Sclerosis 2007; 13: S49—S52. http://msj.sagepub.com

Profile of HBV polymerase gene mutations during entecavir treatment in patients with chronic hepatitis B

BACKGROUND/AIMS

We investigated the efficacy of entecavir (ETV) monotherapy in 54 naïve patients and 27 lamivudine (LMV) and/or adefovir (ADV) experienced patients.

METHODS

Eighty-one chronic hepatitis B patients with a viral load above 4 log 10 copies/ml and high levels of serum alanine aminotransferase were treated with ETV 0.5mg daily. The viruses of patients were sequenced before ETV therapy and after every three months of ETV therapy.

RESULTS

Eight LAM-experienced and ADV-experienced patients emerged mutations in the ETV treatment. In one of these experienced patients, the ETV-resistant mutations were detected during ETV treatment, with the virological and the biochemical breakthrough. Two LAM-experienced and ADV-naïve patients were detected mutation during 1-2 years ETV therapy. All three LAM-naïve and ADV-experienced patients were detected mutations in the ETV treatment. Five in fifty for LAM-naïve and ADV-naïve patients showed mutations in the ETV monotherapy.

CONCLUSIONS

ETV has a high genetic barrier to resistance and the efficacy in LAM-experienced and/or ADV-experienced patients were much lower than in naïve patients.

ADVANCED LIVER INJURY IN PATIENTS WITH CHRONIC HEPATITIS B AND VIRAL LOAD BELOW 2,000 IU/mL

Introduction:

According to the guidelines, the viral load of 2,000 IU/mL is considered the level to differentiate between inactive carriers and HBeAg(-) chronic hepatitis B patients. Even so, liver damage may be present in patients with lower viral load levels, mainly related to regional variations. This study aims to verify the presence of liver injury in patients with viral load below 2,000 IU/mL.

Methods:

Patients presenting HBsAg(+) for more than six months, Anti-HBe(+)/HBeAg(-), viral load below 2,000 IU/mL and serum ALT levels less than twice the upper limit of normality underwent liver biopsy. Clinical and laboratory characteristics were evaluated in relation to the degree of histologic alteration. Liver injury was considered advanced when F ≥ 2 and/or A ≥ 2 by the METAVIR classification.

Results:

11/27 (40.7%) patients had advanced liver injury, with a mean viral load of 701.0 (± 653.7) IU/mL versus 482.8 (± 580.0) IU/mL in patients with mild injury. The comparison between the mean values of the two groups did not find a statistical difference (p = 0.37). The average of serum aminotransferases was not able to differentiate light liver injury from advanced injury.

Conclusions:

In this study, one evaluation of viral load did not exclude the presence of advanced liver damage. Pathologic assessment is an important tool to diagnose advanced liver damage and should be performed in patients with a low viral load to indicate early antiviral treatment.

In-house quantitative real-time PCR for the diagnosis of hepatitis B virus and hepatitis C virus infections

The quantification of viral nucleic acids in serum by real-time PCR plays an important role in diagnosing hepatitis B virus and hepatitis C virus infection. In this study, we developed an assay using specific primers and probes to quantify hepatitis B virus DNA or hepatitis C virus RNA in serum from infected patients. For standardization and validation of the assay, an international panel of hepatitis B virus/hepatitis C virus and standard plasmids was used. A correlation coefficient of 0.983 and 0.963 for hepatitis B virus and hepatitis C virus, respectively, was obtained based on cycle threshold values and concentrations of DNA or RNA. The standard curve showed a linear relationship from 19 IU/mL to 1.9 × 10⁹ IU/mL of serum, with a coefficient of determination (r²) of 0.99. In sera from patients infected with hepatitis B virus or hepatitis C virus viral loads (19 IU/mL and 1.9 × 10⁹ IU/mL), we quantified viral loads with a detection limit of 1.9 × 10² IU/mL. The real-time quantitative PCR assay developed in this study provides an ideal system for routine diagnosis and confirmation of indeterminate serological results, especially in immunosuppressed patients.

Recent advances in molecular diagnostics of hepatitis B virus

Hepatitis B virus (HBV) is one of the important global health problems today. Infection with HBV can lead to a variety of clinical manifestations including severe hepatic complications like liver cirrhosis and hepatocellular carcinoma. Presently, routine HBV screening and diagnosis is primarily based on the immuno-detection of HBV surface antigen (HBsAg). However, identification of HBV DNA positive cases, who do not have detectable HBsAg has greatly encouraged the use of nucleic acid amplification based assays, that are highly sensitive, specific and are to some extent tolerant to sequence variation. In the last few years, the field of HBV molecular diagnostics has evolved rapidly with advancements in the molecular biology tools, such as polymerase chain reaction (PCR) and real-time PCR. Recently, apart of PCR based amplification methods, a number of isothermal amplification assays, such as loop mediated isothermal amplification, transcription mediated amplification, ligase chain reaction, and rolling circle amplification have been utilized for HBV diagnosis. These assays also offer options for real time detection and integration into biosensing devices. In this manuscript, we review the molecular technologies that are presently available for HBV diagnostics, with special emphasis on isothermal amplification based technologies. We have also included the recent trends in the development of biosensors and use of next generation sequencing technologies for HBV.

Comparison of the Abbott RealTime HBV assay with the Roche Cobas AmpliPrep/Cobas TaqMan HBV assay for HBV DNA detection and quantification

BACKGROUND

Measurement of hepatitis B virus (HBV) DNA levels is essential in the clinical management of patients with chronic HBV infection. Performance and accuracy of quantitation for HBV DNA are therefore critical in clinical practice.

OBJECTIVES

We aimed to compare and evaluate the performance characteristics of two HBV DNA quantitative assays: Abbott RealTime HBV (RealTime assay) and Cobas AmpliPrep/Cobas TaqMan HBV assays 2.0 (TaqMan assay).

STUDY DESIGN

Serum samples from 220 HBV-infected patients were collected. Performance characteristics of the HBV DNA quantitative assays, including sensitivity, linearity, and reproducibility were measured. The assays were compared based on the viral status, including HBeAg, genotype, core promoter and pre-core region mutations.

RESULTS

The RealTime assay had a sensitivity and specificity of 98.2% and 100%, respectively. The intra-assay coefficients of variation of serum samples ranged from 0.00% to 11.25% for the RealTime assay and 1.22% to 8.22% for TaqMan assay. Paired quantitative results showed excellent correlation by linear regression analysis (R(2)=0.961), good level of agreement with a mean difference of 0.31log10IU/mL, and limits of agreement of -0.62 to 1.24log10IU/mL, irrespective of HBeAg, genotype, core promoter and pre-core region mutation-specific differences. In this study, a difference of ≥1log10IU/mL between the two assays was observed in 8.6% of the samples. Genotype B and average HBV DNA levels of <3log10IU/mL were significant associated factors of this discordance.

CONCLUSIONS

The Abbott assay delivered high performance for HBV DNA quantification and correlated extremely well with the TaqMan assay, irrespective of viral status.

Comparison of currently available assays for detection of hepatitis B virus DNA in the routine diagnostic laboratory

Infection with the hepatitis B virus (HBV) continues to present diagnostic and therapeutic challenges worldwide. Today, many routine diagnostic laboratories have implemented assays based on molecular techniques for the detection of HBV DNA. However, the standard algorithm for specific diagnosis of HBV infection still relies on serologic testing. Molecular assays are employed for pretreatment evaluation, clinical staging and monitoring of antiviral therapy. Furthermore, molecular methods are essential for identification of mutations in the HBV genome. Although a continuous improvement of assay performance has been observed during recent years, lack of comparability of different molecular assays remains a problem to be resolved in the future. The limited range of linearity when employing conventional PCR will be overcome by using real-time assays.

Comparison of Hybrid Capture 2 Assay with Real-time-PCR for Detection and Quantitation of Hepatitis B Virus DNA

Background

Both real-time-polymerase chain reaction (PCR) and hybrid capture 2 (HC2) assay can detect and quantify hepatitis B virus (HBV) DNA. However, real-time-PCR can detect a wide range of HBV DNA, while HC2 assay could not detect lower levels of viremia. The present study was designed to detect and quantify HBV DNA by real-time-PCR and HC2 assay and compare the quantitative data of these two assays.

Materials and methods

A cross-sectional study was conducted in between July 2010 and June 2011. A total of 66 serologically diagnosed chronic hepatitis B (CHB) patients were selected for the study. Real-time-PCR and HC2 assay was done to detect HBV DNA. Data were analyzed by statistical Package for the social sciences (SPSS).

Results

Among 66 serologically diagnosed chronic hepatitis B patients 40 (60.61%) patients had detectable and 26 (39.39%) had undetectable HBV DNA by HC2 assay. Concordant results were obtained for 40 (60.61%) out of these 66 patients by real-time-PCR and HC2 assay with mean viral load of 7.06 ± 1.13 log₁₀ copies/ml and 6.95 ± 1.08 log₁₀ copies/ml, respectively. In the remaining 26 patients, HBV DNA was detectable by real-time-PCR in 20 patients (mean HBV DNA level was 3.67 ± 0.72 log₁₀ copies/ml. However, HBV DNA could not be detectable in six cases by the both assays. The study showed strong correlation (r = 0.915) between real-time-PCR and HC2 assay for the detection and quantification of HBV DNA.

Conclusion

HC2 assay may be used as an alternative to real-time-PCR for CHB patients.

How to cite this article: Majid F, Jahan M, Moben AL, Tabassum S. Comparison of Hybrid Capture 2 Assay with Real-time-PCR for Detection and Quantitation of Hepatitis B Virus DNA. Euroasian J Hepato-Gastroenterol 2014;4(1):31-35.

Mucocutaneous blood contact: blood release behavior of safety peripheral intravenous catheters

BACKGROUND

Protection against needlestick injuries has significantly improved in recent years thanks to so-called "safety devices." However, a potential drawback occasionally reported by users is a risk of blood splashing. If this blood comes in contact with the mucous membranes, it could lead to an infection.

METHODS

Five safety peripheral intravenous catheter brands were examined in a laboratory test. To simulate the extreme situations, which may arise through human use, the introducer needle was withdrawn from the catheter at 2 different angles whereby an industrial robot was used to simulate the sequence of this movement. Each brand was tested 30 times. The experiment was carried out using radioactively labeled human whole blood. The measurements for the transmitted volume of blood was taken both from an artificial head and from a surface measuring 18.5 cm by 26.5 cm at a height of 30 cm above the catheter; scintigraphy was used to take the measurements.

RESULTS

The volume of blood droplets potentially splashing into the mucous membranes was in the range of 1 nL.

CONCLUSION

For normal virus concentrations in the blood of sick patients, this dose is too small to cause hepatitis C and HIV.

Identification of optimal target gene regions for hepatitis B virus genotyping by DNA sequencing

OBJECTIVES

DNA sequencing is the gold standard for hepatitis B virus (HBV) genotyping. We investigated the intergenotypic discriminatory capabilities of various target gene regions over the entire HBV genome, introducing a novel data evaluation approach generally applicable in viral genotyping.

METHODS

Complete genome sequences of seventy HBV variants obtained from the sera of 50 Syrian patients were determined and assigned GenBank accession No. from JN257148 to JN257217. Nucleotide sequence contigs were analyzed together with the NCBI reference genome set of HBV genotypes. Nine target gene regions were analyzed by phylogenetic and scored BLAST analyses. Thirty-one overlapping 300-bp sequence segments over the entire genome were also analyzed using a scored BLAST analysis, and intergenotypic discriminatory capabilities were statistically estimated for each.

RESULTS

Intergenotype discrimination was extremely significant when targeting either the complete genome, the entire coding sequence of either P or S genes, or any 300-bp sequence segment over the coding sequences of S protein or the polymerase N-terminal domain. Interestingly, intergenotypic discriminatory capability correlated negatively with intragenotype variation.

CONCLUSIONS

The intragenotypic conservation of certain target gene regions determines the intergenotypic discriminatory capability and allows reliable genotyping with relatively short segments. Our referential genome-wide tabulated guide allows for selecting candidate target gene regions for sequencing-based HBV genotyping. © 2013 S. Karger AG, Basel.

Protocol for the use of light upon extension real-time PCR for the determination of viral load in HBV infection

Real-time PCR has engendered wide acceptance for quantitation of hepatitis B virus (HBV) DNA in the blood due to its improved rapidity, sensitivity, reproducibility, and reduced contamination. Here we describe a cost-effective and highly sensitive HBV real-time quantitative assay based on the light upon extension real-time PCR platform and a simple and reliable HBV DNA preparation method using silica-coated magnetic beads.

Comprehensive analysis of the prevalence of hepatitis B virus escape mutations in the major hydrophilic region of surface antigen

Escape mutations in the major hydrophilic region (MHR) of hepatitis B surface antigen (HBsAg) are reported widely worldwide; these mutations lead to diagnostic problems, emergence of vaccine-escape mutants, and hepatitis B immunoglobulin (HBIG) therapy failure. However, the prevalence of these mutations in different genotypes remains to be studied systematically. In the current study, 11,221 non-redundant hepatitis B virus (HBV) sequences of 8 genotypes (from A to H), obtained from the National Center for Biotechnology Information (NCBI), were analyzed to determine the prevalence of HBsAg escape mutations that were previously described. Eight important mutations associated with diagnostic failure, P120T, T126S, Q129H, G130N, S143L, D144A, and G145A/R, were prevalent in one or more genotypes, with the frequency of no less than 1%. With regard to escape variants that evade vaccine or immunoglobulin therapy, mutations were located mainly at positions 120, 126, 129, 130, 133, 134, 137, 140, 143, 144, and 145. The majority of such mutations showed genotypic heterogeneity, indicating the different distribution of the escape mutations. Most of the escape mutations clustered in the "a" determinant, indicating that this region was more likely to be affected by immune selection or antiviral therapy than other regions. Understanding the prevalence and heterogeneity of escape mutations could provide useful guidance for the improvement of diagnostic assays, design of new vaccines, and prevention of failure of HBIG therapy.

Comparison of three Roche hepatitis B virus viral load assay formats

Two FDA-approved (in vitro diagnostic [IVD]) hepatitis B virus (HBV) viral load assays, the manual Cobas TaqMan HBV Test for use with the High Pure System (HP) and the automated Cobas AmpliPrep/Cobas TaqMan HBV Test v2.0 (CAP/CTM), were compared to a modified (not FDA-approved) version of the HP assay by automating the DNA extraction using the Total Nucleic Acid Isolation (TNAI) kit on the Cobas AmpliPrep. On average, CAP/CTM measurements were 0.08 log IU/ml higher than HP results (n = 206), and TNAI results were 0.17 log IU/ml higher than HP results (n = 166). The limit of detection (LOD), as determined by probit analysis using dilutions of the 2nd HBV international standard, was 10.2 IU/ml for CAP/CTM. The data sets for HP and TNAI were insufficient for probit analysis; however, there was 100% detection at ≥ 5 or ≥ 10 IU/ml for TNAI and HP, respectively. Linearity was demonstrated between 60 and 2,000,000 IU/ml, with slopes between 0.95 and 0.99 and R(2) values of >0.99 for all assays. Total precision (log percent coefficient of variance [CV]) was between 0.8% and 2.1% at 4.3 log IU/ml and between 1.4% and 4.9% at 2.3 log IU/ml. Correlation of samples, reproducibility, linearity, and LOD were acceptable and similar in all assays. The CAP/CTM assay and, to a lesser extent, the TNAI assay reduced hands-on time due to automation. There were no instances of contamination detected in negative samples during the course of the study, despite testing several samples up to 9.6 log IU/ml. The incidence of false-positive negative controls in HP and CAP/CTM clinical testing was <0.5% over 6 to 7 months of testing.

Defining virologic relapse in chronic hepatitis B

BACKGROUND AND AIMS

Different definitions of virologic relapse (VR) are being used. One way of defining VR is "reappearance of HBV DNA in the serum," while another definition is an "increase in HBV DNA level greater than 1 log in two determinations at least 4 weeks apart." The aim of this study was to see the effectiveness of these two definitions

METHODS

Forty-five HBeAg-positive chronic hepatitis B patients with a virologic response [negative PCR (<12 IU/ml)] who had discontinued therapy were analyzed retrospectively for VR, HBeAg reversion and biochemical flare.

RESULTS

HBV DNA reappeared in the serum (≥12 IU/ml) of all 45 patients (100%). An increase in HBV DNA level greater than 1 log in two determinations at least 4 weeks apart was identified in 20 of 25 patients (80%). Biochemical flare and HBeAg reversion were observed in 18 (40%) and 14 (31%) patients, respectively. Peak off-therapy HBV DNA level was significantly associated with biochemical flare (r=0.758, P<0.001) and HBeAg reversion (r=0.645, P<0.001). Two patients with high initial off-therapy HBV DNA levels (≥4.0 log(10) IU/ml) were reassessed at 4 weeks, and both experienced a biochemical flare and HBeAg reversion. Two patients had an increase in HBV DNA level greater than 1 log at a very low level (1 log to 2 or 3 log), but did not experience biochemical flare or HBeAg reversion during follow-up.

CONCLUSIONS

Reappearance of HBV DNA was universal when sensitive HBV DNA assay was used. Waiting 4 weeks to confirm VR may be harmful for patients with a high HBV DNA level, and was ineffective to indicate re-therapy for patients with increase in HBV DNA at a very low level. There is a need for improved and standardized definitions of VR.

Cerumen as a potential risk for transmission of Hepatitis B virus

Hepatitis B virus (HBV) transmission via blood and other body fluids from infected individuals to healthy people has been largely demonstrated. However, in the current literature, there is little information available on the potential role of cerumen in HBV transmission. Cerumen and blood were collected from 70 patients infected with HBV and 70 volunteer healthy people were selected as the control group, and the samples were evaluated by ELISA and Real-time PCR. All the patients proved positive for HBsAg and anti HBc total. Sixty-one of the 70 cerumen samples of cases (82.1%) and 5 (7%) of controls were positive for HBV DNA with ranges from 1.53 × 102 to 2.9 × 108 and 1.3 × 102-2.6 × 105/ml, respectively. In three patients, the level of HBV DNA in cerumen was higher than that in the serums. The patients who were positive for HBeAg showed a higher rate of HBVDNA in the serum and cerumen.The results of this study showed the level of HBV DNA as a probably indicator of high risk transmission factor, which was present in the cerumen of chronic hepatitis B patients in west of Iran.

A real-time quantitative assay for hepatitis B DNA virus (HBV) developed to detect all HBV genotypes

Hepatitis B virus (HBV) is a major cause of chronic liver disease worldwide. Besides genotype, quantitative analysis of HBV infection is extensively used for monitoring disease progression and treatment. Affordable viral load monitoring is desirable in resource-limited settings and it has been already shown to be useful in developing countries for other viruses such as Hepatitis C virus (HCV) and HIV. In this paper, we describe the validation of a real-time PCR assay for HBV DNA quantification with TaqMan chemistry and MGB probes. Primers and probes were designed using an alignment of sequences from all HBV genotypes in order to equally amplify all of them. The assay is internally controlled and was standardized with an international HBV panel. Its efficacy was evaluated comparing the results with two other methods: Versant HBV DNA Assay 3.0 (bDNA, Siemens, NY, USA) and another real-time PCR from a reference laboratory. Intra-assay and inter-assay reproducibilities were determined and the mean of CV values obtained were 0.12 and 0.09, respectively. The assay was validated with a broad dynamic range and is efficient for amplifying all HBV genotypes, providing a good option to quantify HBV DNA as a routine procedure, with a cheap and reliable protocol.

Detection of hepatitis B virus genotypes A to D by the fluorescence polarization assay based on asymmetric PCR

The hepatitis B virus genotypes A and D have global distributions, while the hepatitis B genotypes B and C are predominant in Asia. Individuals infected with genotype C or D have a lower response rate to therapy than individuals infected with genotype A or B. The conventional detections of hepatitis B genotypes A to D, however, have not been used routinely due to technical difficulties and high costs. A simple and cost-effective method for simultaneous detection of the hepatitis B genotypes A to D has been developed. A pair of general primers in the preS region of the hepatitis B were used in an asymmetric PCR. Four probes specific for the hepatitis B genotypes A to D labeled with different fluorophores hybridized, respectively with their target amplicons, and the hybridization increased the fluorescence polarization (FP) values. The genotypes were determined by the increased fluorescence polarization values. DNA extracted from 1398 samples was detected by the FP and the type-specific PCR assay in parallel. No significance difference was found between the two methods.

Nuclease-resistant double-stranded DNA controls or standards for hepatitis B virus nucleic acid amplification assays

BACKGROUND

Identical blood samples tested using different kits can give markedly different hepatitis B virus (HBV) DNA levels, which can cause difficulty in the interpretation of viral load. A universal double-stranded DNA control or standard that can be used in all commercial HBV DNA nucleic acid amplification assay kits is urgently needed. By aligning all HBV genotypes (A-H), we found that the surface antigen gene and precore-core gene regions of HBV are the most conserved regions among the different HBV genotypes. We constructed a chimeric fragment by overlapping extension polymerase chain reaction and obtained a 1,349-bp HBVC+S fragment. We then packaged the fragment into lambda phages using a traditional lambda phage cloning procedure.

RESULTS

The obtained armored DNA was resistant to DNase I digestion and was stable, noninfectious to humans, and could be easily extracted using commercial kits. More importantly, the armored DNA may be used with all HBV DNA nucleic acid amplification assay kits.

CONCLUSIONS

The lambda phage packaging system can be used as an excellent expression platform for armored DNA. The obtained armored DNA possessed all characteristics of an excellent positive control or standard. In addition, this armored DNA is likely to be appropriate for all commercial HBV DNA nucleic acid amplification detection kits. Thus, the constructed armored DNA can probably be used as a universal positive control or standard in HBV DNA assays.

A novel real-time PCR assay for determination of viral loads in person infected with hepatitis B virus

A novel LUX (Light Upon eXtension) primer-based real-time PCR assay was developed and evaluated in this study, which was designed to provide a cost-effective, specific and highly sensitive method for viral load determination of hepatitis B virus (HBV). The assay employed an effective and rapid nucleic acid extraction system based on magnetic beads. To evaluate its efficacy, this new viral DNA preparation method was compared with QIAamp Blood Mini Kit and the results showed a good correlation (r=0.971; P<0.001). The performance of the LUX real-time assay was validated by testing serial dilutions of HBV plasmid DNA (5 to 5 x 10(8)copies/reaction) and a good linear relationship was obtained between the Ct values and the log(10) concentration of the HBV DNA. The assay possessed high sensitivity and the detection limit of this system was as few as 25 copies/ml of serum. A total of 91 positive serum samples were detected to evaluate further the assay and the high specificity was confirmed by melting curve analysis. This assay provides an ideal tool for monitoring the treatment efficacy and studying the relationship between HBV viral load and the stage of disease.

Impact of hepatitis B virus genotypes and surface antigen variants on the performance of HBV real time PCR quantification

Quantitative PCR assays used to monitor hepatitis B virus (HBV) load differ in their ability to detect different HBV variants. This study evaluated the performance of the Abbott RT PCR assay for quantitating DNA from different HBV genotypes and from HBV variants bearing HBsAg gene mutations. The study was performed on a randomly-selected sample with a viral load >6logIU/mL for each genotype and on 25 HBsAg variants. Each sample was assayed using the Abbott RT assay and with the Roche Cobas AmpliPrep-Cobas TaqMan as a reference method. All HBV genotypes were detected with the Abbott RT assay with an equivalent dynamic range (1-8logIU/mL). For each genotype, the data suggest that the assay was linear over the entire dilution range (r(2): 0.985-0.995). For the 25 HBsAg variants, viral titres determined with the two assays correlated well (r(2): 0.929). The mean difference between the two methods was -0.295 (95% CI: -0.520 to -0.071). The difference was lower than 1log unit in all but two cases. In conclusion, the Abbott RT assay can detect and quantify DNA from different HBV variants with equivalent performance and is thus suitable for routine monitoring of patients with chronic HBV infections.

Genesis of hepatic fibrosis and its biochemical markers

Liver fibrosis is characterized by an abnormal hepatic accumulation of extracellular matrix (ECM) that results from both increased deposition and reduced degradation of collagen fibres. Fibrotic liver injury results in activation of the hepatic stellate cell (HSC). Surrogate markers are gradually being substituted for biomarkers that reflect the complex balance between synthesis and degradation of the extracellular matrix. Once the hepatic stellate cell is activated, the preceding matrix changes and recurrent injurious stimuli will perpetuate the activated state. The ECM directs cellular differentiation, migration, proliferation and fibrogenic activation or deactivation. The metabolism of the extracellular matrix is closely regulated by matrix metalloproteinases (MMP) and their specific tissue inhibitors (TIMP). Although liver biopsy combined with connective tissue stains has been a mainstay of diagnosis, there is a need for less invasive methods. These diagnostic markers should be considered in combination with liver function tests, ultrasonography and clinical manifestations.

[Performance evaluation of Abbott RealTime HBV Quantification Kit for HBV viral load by real-time PCR]

BACKGROUND

Hepatitis B virus (HBV) DNA quantification is necessary for starting and monitoring of antiviral therapy in patients with chronic hepatitis B. This study was intended to assess the clinical performance of Abbott RealTime HBV Quantification kit (Abbott Laboratories, USA).

METHODS

The performance was evaluated in terms of precision, linearity, detection sensitivity, cross-reactivity, and carry-over. A correlation with the Real-Q HBV Quantification kit (BioSewoom Inc., Korea) was also examined using serum samples from 64 patients diagnosed with chronic hepatitis B and underwent lamivudine therapy in Asan Medical Center. We verified the trueness of the system by comparing the outputs with the assigned values of the BBI panel (BBI Diagnostics, USA).

RESULTS

Within-run and between-run coefficients of variation (CV) were 3.56-4.71% and 3.03-4.98%, respectively. Linearity was manifested ranging from 53 to 10(9)copies/mL and the detection sensitivity was verified to be 51 copies/mL. None of hepatitis C virus showed cross-reactivity. No cross-contamination occurred when negative and positive samples were alternatively placed in a row. It showed a good correlation with the Real-Q HBV (r(2)=0.9609) and the test results for the BBI panel were also well agreed to the assigned values (r(2)=0.9933).

CONCLUSIONS

The performance of Abbott RealTime HBV Quantification kit was excellent; thus, it should be widely used in starting and monitoring of antiviral therapy in Korean patients with chronic hepatitis B.

Experience of German Red Cross blood donor services with nucleic acid testing: results of screening more than 30 million blood donations for human immunodeficiency virus-1, hepatitis C virus, and hepatitis B virus

BACKGROUND

The risk of transfusion-transmitted human immunodeficiency virus-1 (HIV-1), hepatitis C virus (HCV), and hepatitis B virus (HBV) infections is predominantly attributable to donations given during the early stage of infection when diagnostic tests may fail. In 1997, nucleic acid amplification technique (NAT)-testing was introduced at the German Red Cross (GRC) blood donor services to reduce this diagnostic window period (WP).

STUDY DESIGN AND METHODS

A total of 31,524,571 blood donations collected from 1997 through 2005 were screened by minipool NAT, predominantly with pool sizes of 96 donations. These donations cover approximately 80 percent of all the blood collected in Germany during that period. Based on these data, the WP risk in the GRC blood donor population was estimated by using a state-of-the-art mathematic model.

RESULTS

During the observation period, 23 HCV, 7 HIV-1, and 43 HBV NAT-only-positive donations were detected. On the basis of these data and estimated pre-NAT infectious WPs, the residual risk per unit transfused was estimated at 1 in 10.88 million for HCV (95% confidence interval [CI], 7.51-19.72 million), 1 in 4.30 million for HIV-1 (95% CI, 2.39-21.37 million), and 1 in 360,000 for HBV (95% CI, 0.19-3.36 million). Based on observed cases of breakthrough infections, the risk of transfusion-related infections may be even lower.

CONCLUSION

The risk of a blood recipient becoming infected with HCV, HIV-1, or HBV has reached an extremely low level. Introduction of individual donation testing for HCV and HIV-1 would have a marginal effect on interception of WP donations.

Comparison of real-time polymerase chain reaction with the COBAS Amplicor test for quantitation of hepatitis B virus DNA in serum samples

AIM: To compare the clinical performance of a real-time PCR assay with the COBAS Amplicor Hepatitis B Virus (HBV) Monitor test for quantitation of HBV DNA in serum samples.

METHODS: The reference sera of the Chinese National Institute for the Control of Pharmaceutical and Biological Products and the National Center for Clinical Laboratories of China, and 158 clinical serum samples were used in this study. The linearity, accuracy, reproducibility, assay time, and costs of the real-time PCR were evaluated and compared with those of the Cobas Amplicor test.

RESULTS: The intra-assay and inter-assay variations of the real-time PCR ranged from 0.3% to 3.8% and 1.4% to 8.1%, respectively. The HBV DNA levels measured by the real-time PCR correlated very well with those obtained with the COBAS Amplicor test (r = 0.948). The real-time PCR HBV DNA kit was much cheaper and had a wider dynamic range.

CONCLUSION: The real-time PCR assay is an excellent tool for monitoring of HBV DNA levels in patients with chronic hepatitis B.

Are there benefits of simultaneous root colonization by different arbuscular mycorrhizal fungi?

Arbuscular mycorrhizal fungal (AMF) communities were established in pots using fungal isolates from a single field in Switzerland. It was tested whether multispecies mixtures provided more phosphorus and supported greater plant growth than single AMF species. Two host plants, medic (Medicago truncatula) and leek (Allium porrum), were inoculated with three AMF species (Glomus mosseae, G. claroideum and G. intraradices), either separately or in mixtures. The composition of the AMF communities in the roots was assessed using real-time PCR to determine the copy number of large ribosomal subunit genes. Fungal communities in the roots were usually dominated by one AMF species (G. mosseae). The composition of the communities depended on both plant identity and the time of harvest. Leek colonized by a mixture of G. claroideum and G. intraradices acquired more P than with either of the two AMF separately. Direct evidence is provided for functional complementarity among species within the AMF community colonizing a single root system. Competition among the species poses a major challenge in interpreting experiments with mixed inoculations, but this is greatly facilitated by use of real-time PCR.

Antiviral therapy of chronic hepatitis B: prevention of drug resistance

The emergence of viral resistance during treatment is becoming an important clinical issue for hepatitis B virus (HBV) antiviral therapy. Considerable progress has been achieved in the efficacy of treatment, with the development of new drugs that allow a sustained suppression of HBV replication, or at least maintain the viral load below a clinically relevant threshold. Although most drugs currently registered for the treatment of chronic hepatitis B are effective in suppressing viral load, long-term therapy is required to avoid viral reactivation and progression of liver disease. Because of the variability of the HBV genome, such long-term treatments are associated with the emergence of resistant viral strains, which may compromise the initial clinical benefit of the treatment.

Characterization of a new sensitive PCR assay for quantification of viral DNA isolated from patients with hepatitis B virus infections

Sensitive and accurate quantification of hepatitis B virus (HBV) DNA is necessary for monitoring patients with chronic hepatitis receiving antiviral therapy in order to determine treatment response and to adapt therapy in case of inadequate virologic control. The development of quantitative PCR assays has been crucial in meeting these needs. The objective of this study was to compare the performance of a new real-time PCR assay (Abbott RealTime) for HBV DNA with that of three other commercial assays for the detection of HBV DNA. These were the Versant 3.0 branched-chain DNA assay, the Cobas Amplicor HBV Monitor test, and the Cobas AmpliPrep-Cobas TaqMan hepatitis B virus assay (CAP-CTM). HBV DNA was measured in blood samples taken from two cohorts of patients with chronic hepatitis. HBV DNA levels measured with the Abbott RealTime assay were highly correlated with those measured with the other three tests over their respective dynamic ranges (r, 0.88 to 0.96). The sensitivity (detection limit, 10 IU/ml) and dynamic range of the Abbott RealTime assay (10(1) to 10(9) IU/ml) was superior to that of the Versant assay. The RealTime assay recognized both HBV strains belonging to genotypes A to G and those bearing polymerase gene mutations equivalently. In conclusion, this study demonstrates the utility of the Abbott RealTime assay for monitoring HBV DNA levels in patients with chronic hepatitis B. Its sensitivity and wide dynamic range should allow optimal monitoring of antiviral therapy and timely treatment adaptation.

Molecular testing in the diagnosis and management of chronic hepatitis B

Hepatitis B virus (HBV) is an enveloped virus with a small (3.2-kb) partially double-stranded DNA genome that causes acute and chronic infections. The impact of these infections on public health worldwide is enormous, with an estimated prevalence of 2 billion acute infections and 360 million chronic infections globally. This review focuses on chronic hepatitis B and the molecular assays used in its diagnosis and management. Background information, including that about features of the hepatitis B virion, viral replication, and epidemiology of infection, that is important for understanding chronic hepatitis B and molecular diagnostic tests for HBV is provided. To facilitate an understanding of the utility of molecular testing for chronic hepatitis B, the four stages of chronic hepatitis B infection that are currently recognized, as well as an additional entity, occult hepatitis B, that can be diagnosed only by sensitive nucleic acid amplification methods, are reviewed in detail, including available therapeutic agents. The molecular diagnostic content focuses on tests for HBV DNA quantification, genotyping, and mutation detection (including precore/core promoter and antiviral resistance mutations). The discussion of these tests encompasses their current utility and performance characteristics, drawing from current clinical guidelines and other studies from the literature. In recognition of the continual evolution of this field, the final section describes emerging molecular markers with future diagnostic potential.

Prevalence of low-level hepatitis B viremia in patients with HBV surface antigen-negative hepatocellular carcinoma with and without hepatitis C virus infection in Japan: analysis by COBAS TaqMan real-time PCR

OBJECTIVES

The effect of circulating low-level hepatitis B virus (HBV), defined as one of the states of 'occult HBV infection', on the development of hepatocellular carcinoma (HCC) in HBV surface antigen (HBsAg)-negative patients is controversial. In addition, the prevalence of occult HBV infection strongly depends on the sensitivity of the HBV detection method. We investigated the prevalence of low-level HBV in the serum of HBsAg-negative patients with HCC using a newly developed, sensitive method based on real-time polymerase chain reaction.

METHODS

Serum was examined for HBV DNA in 132 patients with HBsAg-negative HCC (95 with hepatitis C virus [HCV] infection and 37 without detectable hepatitis virus infection) with the COBAS TaqMan HBV test, of which the 95% hit rate is 35 copies/ml (6.7 IU/ml).

RESULTS

Low-level HBV DNA was detected in 2 of 95 (2.1%) patients with HCV-related HCC and 1 of 37 (2.7%) patients with non-viral HCC.

CONCLUSION

The prevalence of the detection of circulating low-level HBV was low in both HBsAg-negative HCC patients with HCV infection and those without detectable hepatitis virus, even with the use of the most sensitive method for the detection of HBV. Circulating low-level HBV does not appear to play an important role in hepatocarcinogenesis in HBsAg-negative HCC.

Detection and quantification of hepatitis B virus DNA by SYBR green real-time polymerase chain reaction

A single-round real-time polymerase chain reaction (PCR) assay based on SYBR green dye technology for the detection and quantification of hepatitis B virus (HBV) DNA in serum was evaluated and compared with a qualitative nested PCR and the Cobas Amplicor HBV Monitor assay (Roche Molecular Diagnostics, Milan, Italy). The performance of the real-time PCR assay was evaluated in a routine clinical laboratory setting with a total of 212 clinical specimens. The sensitivity of the real-time PCR corresponded to 31 IU/ml (70 copies/ml), and comparison with the qualitative nested PCR showed significant concordance for 94% of samples. The linear curve over 7 log units, spanning 10(3)-10(9) IU/ml (2.28 x 10(3) to 2.28 x 10(9) copies/ml), was observed in the quantitative determination. The interexperimental variability coefficient of the assay ranged from 0.22 to 0.39 and the intraexperimental variability coefficient from 0.24 to 0.41. By excluding values outside of the dynamic ranges of both tests, the HBV Monitor and the real-time PCR gave an agreement within +/-1 log unit for 90% of samples, while those for the remaining 10% were found to be above 1 log unit but less than 1.5 log units. When the results inside and outside the dynamic range of the HBV Monitor were examined, 90% of the results were in agreement. In conclusion, the real-time PCR based on SYBR green technology proved suitable for routine diagnostic purposes, showing good sensitivity, high specificity, high reproducibility, and good linearity over a broad dynamic range of quantification.

Statistical methods for determining the accuracy of quantitative polymerase chain reaction-based tests

Quantitative polymerase chain reaction (PCR)-based tests are used in several different scientific fields to determine levels of a target DNA sequence of interest (the target molecule). The accuracy of quantitative PCR-based tests can be assessed by using the assay to determine the number of copies of the target molecule in a sample with a known concentration of the target molecule. For example, a sample with a known concentration of a target DNA sequence is serially diluted into replicate aliquots and these are tested to determine if the observed quantity of the target is close to the expected quantity (given the concentration in the original sample and the dilution). Statistical methods that are conventionally used to assess the accuracy of these assays do not take into account the variability in the number of target molecules in each aliquot from the original sample. We develop methods that take into account this extra variation and which determine the accuracy of quantitative PCR-based tests in estimating the number of target molecules based on a set of assays of serial dilutions from an original sample with a known concentration of target molecules. These methods are applied to data from an experiment to test the accuracy of a real-time PCR assay at low HIV-1 DNA copy levels.

COBAS AmpliPrep-COBAS TaqMan hepatitis B virus (HBV) test: a novel automated real-time PCR assay for quantification of HBV DNA in plasma

Success in antiviral therapy for chronic hepatitis B is supported by highly sensitive PCR-based assays for hepatitis B virus (HBV) DNA. Nucleic acid extraction from biologic specimens is technically demanding, and reliable PCR results depend on it. The performances of the fully automatic system COBAS AmpliPrep-COBAS TaqMan 48 (CAP-CTM; Roche, Branchburg, NJ) for HBV DNA extraction and real-time PCR quantification were assessed and compared to the endpoint PCR COBAS AMPLICOR HBV monitor (CAHBM; Roche). Analytical evaluation with a proficiency panel showed that CAP-CTM quantitated HBV DNA levels in one single run over a wide dynamic range (7 logs) with a close correlation between expected and observed values (r = 0.976, interassay variability below 5%). Clinical evaluation, as tested with samples from 92 HBsAg-positive patients, demonstrated excellent correlation with CAHBM (r = 0.966, mean difference in quantitation = 0.36 log(10) IU/ml). CAP-CTM detected 10% more viremic patients and longer periods of residual viremia in those on therapy. In lamivudine (LAM)-resistant patients, the reduction of HBV DNA after 12 months of Adefovir (ADF) was higher in the combination (LAM+ADF) schedule than in ADF monotherapy (5.1 logs versus 3.5 logs), suggesting a benefit in continuing LAM. CAP-CTM detected HBV DNA in liver biopsy samples from 15% of HBsAg-negative, anti-HBcAg-positive graft donors with no HBV DNA in plasma. The amount of intrahepatic HBV DNA was significantly lower in occult HBV infection than in overt disease. CAP-CTM can improve the management of HBV infection and the assessment of antiviral therapy and drug resistance, supporting further insights in the emerging area of occult HBV infection.

A genotype-independent real-time PCR assay for quantification of hepatitis B virus DNA

Accurate quantification of hepatitis B virus (HBV) DNA levels is important for monitoring patients with chronic HBV infection and for assessing their responses to antiviral therapy. This study aimed to develop a real-time PCR assay that is sensitive and can accurately quantify a wide range of HBV DNA levels across the known HBV genotypes. An "in-house" real-time PCR assay using primers and a TaqMan probe in a highly conserved region of the HBV surface gene was designed. The assay was standardized against a WHO standard and validated against plasmids of HBV genotypes A through H. The linear quantification range was approximately 5 x 10(0) to 2.0 x 10(9) IU/ml. Results of samples from patients infected with HBV genotypes A through H tested using our real-time "in-house" PCR assay showed an excellent correlation with those of the Cobas Amplicor HBV Monitor (R2=0.9435) and the Cobas TaqMan HBV (R2=0.9873) tests. We have established a real-time PCR assay that is genotype independent and can accurately quantify a wide range of HBV DNA levels. Further studies of additional samples are ongoing to validate the genotype independence of our assay.

Rapid quantification of hepatitis B virus DNA by real-time PCR using efficient TaqMan probe and extraction of virus DNA

AIM: To rapidly quantify hepatitis B virus (HBV) DNA by real-time PCR using efficient TaqMan probe and extraction methods of virus DNA.

METHODS: Three standards were prepared by cloning PCR products which targeted S, C and X region of HBV genome into pGEM-T vector respectively. A pair of primers and matched TaqMan probe were selected by comparing the copy number and the Ct values of HBV serum samples derived from the three different standard curves using certain serum DNA. Then the efficiency of six HBV DNA extraction methods including guanidinium isothiocyanate, proteinase K, NaI, NaOH lysis, alkaline lysis and simple boiling was analyzed in sample A, B and C by real-time PCR. Meanwhile, 8 clinical HBV serum samples were quantified.

RESULTS: The copy number of the same HBV serum sample originated from the standard curve of S, C and X regions was 5.7 × 10⁴/mL, 6.3 × 10²/mL and 1.6 × 10³/mL respectively. The relative Ct value was 26.6, 31.8 and 29.5 respectively. Therefore, primers and matched probe from S region were chosen for further optimization of six extraction methods. The copy number of HBV serum samples A, B and C was 3.49 × 10⁹/mL, 2.08 × 10⁶/mL and 4.40 × 10⁷/mL respectively, the relative Ct value was 19.9, 30 and 26.2 in the method of NaOH lysis, which was the efficientest among six methods. Simple boiling showed a slightly lower efficiency than NaOH lysis. Guanidinium isothiocyanate, proteinase K and NaI displayed that the copy number of HBV serum sample A, B and C was around 10⁵/mL, meanwhile the Ct value was about 30. Alkaline failed to quantify the copy number of three HBV serum samples. Standard deviation (SD) and coefficient variation (CV) were very low in all 8 clinical HBV serum samples, showing that quantification of HBV DNA in triplicate was reliable and accurate.

CONCLUSION: Real-time PCR based on optimized primers and TaqMan probe from S region in combination with NaOH lysis is a simple, rapid and accurate method for quantification of HBV serum DNA.

Expertise of laboratories in viral load quantification, genotyping, and precore mutant determination for hepatitis B virus in a multicenter study

A national evaluation study was performed in 14 specialized laboratories with the objective of assessing their capacities to provide (i) hepatitis B virus (HBV) viral loads (VL), (ii) HBV genotypes, and(iii) identification of precore/core mutants. The panel consisted of 12 HBV DNA-positive samples with VLs from 2.8 to 9.1 log(10) copies/ml, different HBV genotypes (A to F), and 3 mutant and 9 wild-type samples at nucleotide 1896. The coefficients of variation of the mean VLs ranged from 2.4% to 10.4% with the Cobas HBV Monitor assay, from 1.8% to 5.5% with the Cobas TaqMan 48, from 1.5 to 26.2% with RealArt HBV PCR, and from 0 to 7% with branched DNA (bDNA). The Cobas Monitor assay underestimated the VLs of genotype F samples, with differences ranging from 1.4 to 2.4 log(10) copies/ml. The accuracies of genotype determinations ranged from 33% to 100%, and those of precore mutant determinations ranged from 25 to 100%. This study showed some drawbacks of two widely used assays: (i) Cobas Monitor has a narrow dynamic range and underestimates genotype F sample VLs and (ii) bDNA shows poor sensitivity and may fail to identify patients with low VLs. With higher performance in terms of analytical sensitivity combined with a larger dynamic range and an ability to quantify the main genotypes equally, real-time PCR methods appear more appropriate for accurate monitoring of HBV DNA quantification. Furthermore, the clinical implications of HBV genotyping and the determination of precore/core mutants need to be clearly stated to justify the standardization of these methods.

Evaluation of the COBAS AmpliPrep-total nucleic acid isolation-COBAS TaqMan hepatitis B virus (HBV) quantitative test and comparison to the VERSANT HBV DNA 3.0 assay

Quantitative detection of hepatitis B virus (HBV) in serum or plasma has become the most direct and reliable method for monitoring chronic hepatitis B. Here, we report the performance characteristics of a real-time PCR hepatitis B DNA quantitative assay, the COBAS TaqMan (CTM) HBV test (Roche Diagnostics, Meylan, France), in combination with an automated DNA extraction on the COBAS AmpliPrep (CAP) instrument using the total nucleic acid isolation kit (TNAI kit), a generic reagent for nucleic acid isolation (both from Roche Diagnostics). The linearity, accuracy, and specificity of the CAP-TNAI-CTM HBV test were evaluated using various reference panels and standards (HBV panel 2004 from Quality Control for Molecular Diagnostics, OptiQuant HBV panel from AcroMetrix, WHO International Standard for HBV, and Teragenix hepatitis B genotype panel). Quantitative results show that the CAP-TNAI-CTM HBV test performed well with respect to linearity, accuracy, and reproducibility from at least 100 to 500,000 HBV DNA IU/ml. Based on the log(10) IU of HBV DNA/ml measured, the intra-assay variation ranged from 2.49% to 8.46% and the interassay variation ranged from 1.88% to 7.83%. The test was extremely sensitive and could detect samples containing HBV DNA below the reported quantification threshold (<30 IU/ml). All HBV genotypes were correctly amplified, and no cross-contamination occurred during the automated sample preparation. In addition, 402 human serum samples were tested comparatively to the VERSANT HBV DNA 3.0 assay (bDNA; Bayer Diagnostics, Puteaux, France). The viral load results of the CAP-TNAI-CTM test and bDNA were significantly correlated, but the agreement between the two tests was poor, with large differences between results for individual samples. The hands-on time was estimated to be reduced from 2.30 h with bDNA to 45 min with the CAP-TNAI-CTM test, and up to 84 samples were completely processed within a working day. Overall, the performance characteristics of the CAP-TNAI-CTM test demonstrated that it provides a high-throughput sensitive and reliable method for quantitation of HBV DNA levels in the routine molecular laboratory.

Quantification of hepatitis B virus (HBV) DNA with a TaqMan HBV analyte-specific reagent following sample processing with the MagNA pure LC instrument

TaqMan hepatitis B virus (HBV) analyte-specific reagent (ASR; Roche Molecular Systems, Inc., Branchburg, NJ) is designed for the quantification of HBV DNA in serum or plasma. The performance characteristics of TaqMan HBV ASR following automated sample processing with the MagNA Pure LC instrument (MP; Roche Applied Science, Indianapolis, IN) were evaluated in this study. Analytical sensitivity and precision were assessed with commercially available HBV standards, while clinical serum specimens from HBsAg-seropositive patients and healthy blood donors were used to determine clinical sensitivity, specificity, and correlation with other commercially available assays. Analytical studies yielded a limit of detection of 2.4 IU/ml, with good linearity and correlation (R(2) = 0.9958) with expected HBV DNA titers over a wide range (6.0 x 10(0) to 2.1 x 10(8) IU/ml). Clinical sensitivity and specificity of the assay combined with automated sample processing were both 100%. Comparison of TaqMan HBV ASR and VERSANT HBV DNA 3.0 assay (bDNA; Bayer HealthCare LLC, Tarrytown, NY) results among clinical specimens yielded good correlation (R(2) = 0.9237), with a mean difference in titer of -0.213 log(10) IU/ml (95% confidence interval, -0.678 to 1.10 log(10) IU/ml). The overall test failure rate was 2.0% among 204 clinical serum specimens tested. Total time required for MP sample processing and automated postelution handling of 24 samples was 224 min, with 57 min of actual hands-on time. MP is a reliable, labor-saving platform suitable for use with TaqMan HBV ASR, providing sensitive and accurate quantification of HBV DNA levels over a range of 8 log(10) IU/ml.