Lamivudine resistance of hepatitis B virus masked by coemergence of mutations in probe region of the COBAS AMPLICOR assay

Rapid quantification assay of hepatitis B virus DNA in human serum and plasma by Fully Automated Genetic Analyzer μTASWako g1

Real-time monitoring of serum hepatitis B virus (HBV) levels is essential for the management of patients with chronic HBV infection in clinical practice, including monitoring the resistance of anti-HBV nucleotide analog or the detection of HBV reactivation. In this context, serum HBV deoxyribonucleic acid (DNA) quantification should be rapidly measured. A rapid HBV DNA quantification assay was established on the Fully Automated Genetic Analyzer, μTASWako g1. The assay performs automated sample preparation and DNA extraction, followed by the amplification and detection of quantitative polymerase chain reaction (PCR) combined with capillary electrophoresis (qPCR-CE) on integrated microfluidic chip. This study aimed to evaluate the analytical and clinical performance of HBV DNA assay on the μTASWako g1 platform in human serum and EDTA-plasma. The HBV DNA assay has a linear quantitative range from 20 to 108 IU/mL of HBV DNA with standard deviation (SD) of ≤0.14 log10 IU/mL. The limits of detection of the assay were 4.18 for the serum and 4.35 for EDTA-plasma. The HBV assay demonstrated the equivalent performance in both human serum and EDTA-plasma matrices. The HBV genotypes A to H were detected with an accuracy of ±0.34 log10 IU/mL. In quantification range, the HBV DNA assay was correlated with Roche cobas AmpliPrep/cobas TaqMan Ver2.0 (CAP/CTM v2) (r = 0.964). The mean difference (μTASWako g1-CAP/CTM v2) of the reported HBV DNA was -0.01 log10 IU/mL. Overall, the sensitivity, accuracy, and precision of the μTASWako g1 HBV assay were comparable to the existing commercial HBV DNA assay, and the assay can be completed within 110 min. This evaluation suggests that the HBV DNA assay on the μTASWako g1 is potentially applied for alternative method of the HBV viral load test, in particular with the advantage of the HBV DNA result availability within 2 h, improving the HBV infection management.

Evaluation of the Aptima HBV Quant Assay Compared to Abbott RealTime M2000 HBV Quant Assay and Procleix Ultrio Plus dHBV Assay in Plasma Samples

Analytical performance of hepatitis B virus (HBV) DNA quantitative assay is critical for screening infection and initiating and monitoring antiviral treatment. In this study, the limit of detection (LoD) and linearity of Aptima HBV Quant assay were evaluated, and analytical performance was compared with that of the Abbott RealTime M2000 HBV Quant assay and the Procleix Ultrio Plus dHBV assay in plasma samples. The LoDs for genotypes B, C, and D plasma samples were 2.139 (1.531, 4.520), 3.120 (2.140, 7.373), and 3.330 (2.589, 4.907) IU/mL, respectively. The R² value fitted by linear regression of serially diluted samples less than 2,000 IU/mL was above 0.9. There was no difference in positive rate between Aptima and Abbott or between Aptima and Procleix. Quantitative results of Aptima and Abbott showed good correlation with an r of >0.9 using Spearman analysis, while the quantitative results of Aptima were slightly lower than those of Abbott. Usual mutations in the HBV S region had no impact on Aptima assay. This study showed that Aptima is a dual-targeted transcription-mediated amplification (TMA) assay suitable for HBV DNA detection in clinical practice, with quantitative performance comparable to that of the Abbott RealTime M2000 HBV Quant assay and qualitative performance comparable to that of the Procleix Ultrio Plus dHBV assay.

IMPORTANCE The Aptima HBV Quant assay (Hologic Inc., San Diego, CA, USA) is a dual-target real-time transcription-mediated amplification (RT-TMA) assay. This study aims to evaluate whether this assay is suitable for HBV DNA detection. As a result, the assay showed high sensitivity with LoDs below 3.5 IU/mL. The amplification efficiency of Aptima for samples below 2,000 IU/mL is adequate for clinical practice, with an R² of >0.9 fitted by linear regression. Usual mutations in the HBV S region did not affect the performance of Aptima. Moreover, its performance was comparable to the widely used Abbott RealTime M2000 HBV Quant assay for detecting HBV DNA in plasma specimens. Although not indicated for use as a diagnostic or blood screening assay, the Aptima HBV Quant assay demonstrated comparable qualitative performance to the Procleix Ultrio Plus dHBV system.

Comparison of the Amplisure HBV Quantitative Kit with the Qiagen Artus HBV QS-RGQ Assay for Quantifying Viral DNA in Plasma Samples of Monitoring Cases

BACKGROUND

Monitoring of hepatitis B virus (HBV) viral load has become an essential phase in the treatment of HBV. There are many commercial assays available for HBV viral load quantification. In this study, we have evaluated the performance characteristics of Amplisure® HBV Kit in comparison with the Qiagen artus HBV QS-RGQ kit for HBV DNA quantitation.

METHODS

Comparison of 2 methods was carried out on 200 clinical samples, 150 HBV DNA positive and 50 HBV DNA negative, by a reference method. Results obtained with Amplisure® HBV Kit (Amplisure HBV) were compared using the Qiagen artus HBV QS-RGQ assay results as the comparator method.

RESULT

The overall performance of the Amplisure HBV compared with the comparator method shows positive and negative clinical agreement of 100 and 76%, respectively. Among the 12 qualitative discrepant samples, all positive with Amplisure HBV were sequenced and 10 were below comparator method's LOD. For 5 weak positives (-0.22 to 0.98 log IU/mL), the sequencing failed. The 7 other positives (0.48 to 1.89 log IU/mL) were confirmed positive by sequencing. Quantitative comparison gave an r2 of 0.967 with a mean log difference of 0.09 log10 IU/mL.

CONCLUSION

This study shows that Amplisure® HBV Quantitative Kit shows comparable performance with artus HBV QS-RGQ assays and can be useful in management and therapeutic monitoring of HBV in a clinical practice.

A Highly Prevalent Polymorphism in the Core Region Impairs Quantification of Hepatitis B Virus (HBV) by the cobas TaqMan HBV Assay

The high genetic variability of hepatitis B virus (HBV) can impair DNA quantification. Here, we investigate a major underquantification of HBV by the cobas TaqMan HBV assay (CTM; Roche). In France, between 2005 and 2017, HBV DNA was detected in 3,102 blood donations by use of the CTM (95% limit of detection [LOD₉₅], 4.8 IU/ml). HBV strains were sequenced in the S region (LOD₉₅, ∼30 IU/ml). Concordant (n = 120) and discordant (n = 45) samples were identified according to the agreement between the plasma viral load (pVL) determined by the CTM and sequencing; all samples were also quantified using the RealTime HBV assay (RTH; Abbott). The viral signature, cloning, and mutagenesis were used to characterize the polymorphism responsible for CTM misquantification. A CTM-RTH discordance (>1 log IU/ml) was found in 14/45 samples that had low pVLs and were successfully genotyped (pVL^low genoS⁺). PreC/C clones of concordant (C1, C2) and discordant (D1, D2) strains were used to challenge the CTM. Strains D1 and D2 were highly underquantified (42- and 368-fold). In clones, mutating the region corresponding to the CTM reverse primer from a discordant sequence to a concordant sequence restored the levels of quantification to 24% (D1→C1) and 59% (D2→C1) of theoretical levels, while mutating the sequence of a concordant strain to that of a discordant strain led to 78-fold (C1→D1) and 146-fold (C1→D2) decreases in quantification. Moreover, mutating positions 1961 and 1962 was enough to induce a 5-fold underquantification. We conclude that the CTM underestimates pVLs for HBV strains with mutations in the reverse primer target. Specifically, the polymorphism at nucleotides 1961 and 1962 is naturally present in 4.79 and 4.22% of genotype A and D strains, which are highly frequent in Europe, leading to a 5-fold decrease in quantification. Quantification using the new-generation Roche C4800 assay is not affected by this polymorphism.

HBV DNA Test Among Blood Donations May Require Two Amplification Targets

To analyze the risk and reason of false-negative HBV DNA results of NAT reagents among blood donations of China and discuss the necessity of two amplification targets for HBV DNA tests among donations. In this study, samples that showed discordant results on two commercially available assay platforms were further detected by established in-house methods based on conserved regions of the HBV genome. The HBV concentration of these samples was determined using two commercially available reagents. The samples with high titers of HBV were detected by an in-house method. The samples showing high Ct differences between two regions in the in-house method were further sequenced and aligned with primers and probes. The results showed that the established method has a good detection performance. The mismatch between reverse primers and sample sequences led to decreased detection capacity of S and C regions by the in-house method, but it could be compensated by another region. Among the false-negative samples detected by commercial reagents, most were because of low titers; however, there were 7 samples with HBV DNA concentrations much higher than the LOD of the commercial reagents, which may be due to mismatch of the primer or probe. This study highlights the potential risk of HBV false-negative detection by commercial NAT reagents. The dual-target assay may be helpful for HBV screening and reduce the risk of false-negative detection.

Prediction value of serum HBV large surface protein in different phases of HBV infection and virological response of chronic hepatitis B patients

BACKGROUND

Serum HBV large surface protein (HBV-LP) is an envelope protein that has a close relationship with HBV DNA level. This study is to explore the prediction value of HBV-LP in different phase of HBV infection and during antiviral therapy in chronic hepatitis B (CHB) patients.

METHODS

A retrospective study was conducted in 2033 individuals, which included 1677 HBV infected patients in different phases and 356 healthy controls. HBV-LP, HBV serum markers and HBV DNA were detected by ELISA, CMIA and qRT-PCR, respectively. 85 CHB patients receiving PegIFNα or ETV were divided into virological response (VR) and partial virological response (PVR). The dynamic changes of HBV DNA and HBV-LP were observed.

RESULTS

The level of HBV-LP in 2033 individuals was shown as: HBeAg-positive hepatitis > HBeAg-positive infection > HBeAg-negative hepatitis > HBeAg-negative infection > healthy controls. HBV-LP was positive in all patients whose HBV DNA > 1.0E + 06 IU/ml. When HBsAg was <0.05 IU/ml or >1000 IU/ml, HBV DNAs were all negative if HBV-LP < 1.0 S/CO. When HBsAg was between 0.05 IU/ml and 1000 IU/ml, the consistency of HBV-LP with HBV DNA was 100% in case of HBV-LP > 4.0 S/CO in HBeAg-positive patients and HBV-LP > 2.0 S/CO in HBeAg-negative ones. During antiviral therapy, baseline HBV-LP was lower in VR patients than that in PVR patients. The optimal cut-off points to predict VR by baseline HBV-LP were 32.4 and 28.6 S/CO for HBeAg-positive and HBeAg-negative hepatitis patients, respectively.

CONCLUSIONS

HBV-LP may be a useful marker for distinguishing the different phases of HBV infection. Moreover, baseline HBV-LP level can be used for predicting VR of CHB patients.

Performance of the cobas Hepatitis B virus (HBV) test using the cobas 4800 system and comparison of HBV DNA quantification ability between the COBAS AmpliPrep/COBAS TaqMan HBV test version 2.0 and cobas HBV test

BACKGROUND

Hepatitis B virus (HBV) DNA levels are used to predict the response to therapy, determine therapy initiation, monitor resistance to therapy, and establish treatment success.

OBJECTIVE

To verify the performance of the cobas HBV test using the cobas 4800 system for HBV DNA quantification and to compare the HBV DNA quantification ability between the cobas HBV test and COBAS AmpliPrep/COBAS TaqMan HBV version 2.0 (CAP/CTM v2.0).

STUDY DESIGN

The precision, linearity, and limit of detection of the cobas HBV test were evaluated using the 4th World Health Organization International Standard material and plasma samples. Clinical samples that yielded quantitative results using the CAP/CTM v2.0 and cobas HBV tests were subjected to correlational analysis.

RESULTS

Three hundred forty-nine samples were subjected to correlational analysis, among which 114 samples showed results above the lower limit of quantification. Comparable results were obtained ([cobas HBV test] = 1.038 × [CAP/CTM v2.0]-0.173, r = 0.914) in 114 samples, which yielded values above the lower limit of quantification. The results for 86.8% of the samples obtained using the cobas HBV test were within 0.5 log₁₀ IU/mL of the CAP/CTM v2.0 results. The total precision values against the low and high positive controls were 1.4% (mean level: 2.25 log₁₀ IU/mL) and 3.2% (mean level: 6.23 log₁₀ IU/mL), respectively. The cobas HBV test demonstrated linearity (1.15-6.75 log₁₀ IU/mL, y = 0.95 × 6 + 0.17, r² = 0.994).

CONCLUSION

The cobas HBV test showed good correlation with CAP/CTM v2.0, and had good precision and an acceptable limit of detection. The cobas HBV test using the cobas 4800 is a reliable method for quantifying HBV DNA levels in the clinical setting.

Real-time PCR assays for hepatitis B virus DNA quantification may require two different targets

Background

Quantification Hepatitis B virus (HBV) DNA plays a critical role in the management of chronic HBV infections. However, HBV is a DNA virus with high levels of genetic variation, and drug-resistant mutations have emerged with the use of antiviral drugs. If a mutation caused a sequence mismatched in the primer or probe of a commercial DNA quantification kit, this would lead to an underestimation of the viral load of the sample. The aim of this study was to determine whether commercial kits, which use only one pair of primers and a single probe, accurately quantify the HBV DNA levels and to develop an improved duplex real-time PCR assay.

Methods

We developed a new duplex real-time PCR assay that used two pairs of primers and two probes based on the conserved S and C regions of the HBV genome. We performed HBV DNA quantitative detection of HBV samples and compared the results of our duplex real-time PCR assays with the COBAS TaqMan HBV Test version 2 and Daan real-time PCR assays. The target region of the discordant sample was amplified, sequenced, and validated using plasmid.

Results

The results of the duplex real-time PCR were in good accordance with the commercial COBAS TaqMan HBV Test version 2 and Daan real-time PCR assays. We showed that two samples from Chinese HBV infections underestimated viral loads when quantified by the Roche kit because of a mismatch between the viral sequence and the reverse primer of the Roche kit. The HBV DNA levels of six samples were undervalued by duplex real-time PCR assays of the C region because of mutations in the primer of C region.

Conclusions

We developed a new duplex real-time PCR assay, and the results of this assay were similar to the results of commercial kits. The HBV DNA level could be undervalued when using the COBAS TaqMan HBV Test version 2 for Chinese HBV infections owing to a mismatch with the primer/probe. A duplex real-time PCR assay based on the S and C regions could solve this problem to some extent.

Comparison of the QIAGEN artus HBV QS-RGQ Assay With the Roche COBAS AmpliPrep/COBAS TaqMan HBV Assay for Quantifying Viral DNA in Sera of Chronic Hepatitis B Patients

BACKGROUND

Hepatitis B virus DNA quantification is essential for managing chronic hepatitis B (CHB). We compared the performance of artus HBV QS-RGQ (QIAGEN GmbH, Germany) and CAP/CTM v2.0 HBV assays (Roche Molecular Diagnostics, USA) in CHB patients.

METHODS

A comparative evaluation between two assays was performed with 508 clinical serum samples. Precision, linearity, and the limit of detection (LOD) of QS-RGQ assay was evaluated by using the WHO standard 97/750 and clinical samples.

RESULTS

Detection rates and viral loads as determined QS-RGQ assay were significantly lower than those from the CAP/CTM v2.0 assay (52.8% vs 60.6%; 3.55±1.77 IU/mL vs 4.18±1.89 IU/mL, P<0.0001). The kappa coefficient between qualitative results was 0.79 (95% confidence interval, 0.74 to 0.85). Bland-Altman plot found a mean difference of (QS-RGQ - CAP/CTM v2.0)=-0.63 log₁₀ IU/mL (95% limit of agreement, -1.48 to 0.22). Repeatability and total imprecision (% CV) of the QS-RGQ assay were 1.0% and 1.1% at 2,000 IU/mL, and 0.7% and 1.4% at 20,000 IU/mL, respectively. Linearity of this assay ranged from 31.6 to 1.0±10⁷ IU/mL, and the LOD was 2.95 IU/mL.

CONCLUSIONS

The artus HBV QS-RGQ assay showed good performance but significantly decreased detection rate and viral load compared with CAP/CTM v2.0 assays. This assay recommends using plasma; however, we used stored serum because of the retrospective study design. Usually HBV DNA quantification is performed in plasma or serum, but sample type and clinical relevance of quantitative values should be considered when determining the clinical application of this reagent.

Definition of an HBsAg to DNA international unit conversion factor by enrichment of circulating hepatitis B virus forms

Hepatitis B (HBV) virus infection is characterized by the overproduction of subviral particles (SVP) over infectious Dane particles (VP). Precise regulation of the ratio between these forms is unknown, but its fluctuation may have a clinical impact. An enrichment method was applied to assess the SVP/VP ratio in chronically infected patients (CHB) and to compare the sensitivity of HBs antigen (HBsAg) and DNA detection methods. Plasmas from 9 genotype A-D CHB patients were fractionated on Nycodenz(®) gradients, and both HBV DNA and HBsAg were quantified in each collected fraction using standardized techniques expressed in IU/mL. Infection of primary human hepatocytes (PHHs) was performed with crude or fractionated plasma. Independently of the genotype, all plasmas showed a similar rate-zonal separation profile characterized by a bottom DNA-enriched peak surmounted by HBsAg-enriched fractions. Inoculation of PHH with plasma-derived VP-enriched fractions led to long-lasting production of virus in cell supernatants with a SVP/VP ratio similar to that observed in patient plasmas. In the VP fraction, one IU of HBsAg corresponded to approximately 5 million IU of HBV DNA. Rate-zonal gradient separation directly applied on patient plasma allows a better insight into the distribution of VP in HBeAg-positive CHB carriers. This study highlights the sensitivity difference of the techniques classically used to monitor HBV infection and indicates that VP-associated HBsAg contributes modestly to the overall amount of total circulating HBsAg in CHB. Such a fractionation approach should help to understand the fine regulation of HBsAg production over replication at different stages of CHB.

Abbott RealTime HBV assay is more sensitive in detection of low viral load and little impacted by drug resistant mutation in chronic hepatitis B patients under nucleot(s)ide analogues therapy

BACKGROUND

Selection of drug-resistant strains may lead to failure of HBV antiviral therapy. There is little information whether there is detection difference in drug resistant mutations between different viral load assays of HBV.

OBJECTIVES

This study is aimed to investigate whether there is drug-resistant strains related detection difference between Abbott RealTime HBV (RealTime) and CobasAmpliPrep/CobasTaqMan HBV assays 2.0 (TaqMan).

STUDY DESIGN

One hundred and thirty-four CHB patients who received HBV anti-viral therapy were enrolled. HBV virological markers were tested 3 months apart regularly. Serum HBV DNA levels were determined using the TaqMan and RealTime. YMDD (rt180M and rt204V) mutation was checked in patients who experienced virologic breakthrough (VBT).

RESULTS

The correlation of HBV DNA observed between the RealTime and TaqMan was good for all 571 samples (R2 = 0.797; P<0.001). However, the correlation in the 434 samples with HBV DNA level <3 log10 IU/ml was not as good as in all samples (R2 = 0.457). Overall, 21.5% of samples had a detection difference of ≥ 1 log10 IU/ml with 91.9% of these having HBV DNA level <3 log10 IU/ml. Twenty-four patients experienced VBT. Three of these patients had acquired the YMDD mutation and exhibited discordant viral load results between the two methods tested. In each case, persistent HBV DNA was detected by RealTime and undetectable with TaqMan. Of the patients who experienced a VBT and had acquired YMDD mutation, 4.7% had undetectable HBV DNA by TaqMan while all were detectable with RealTime.

CONCLUSIONS

RealTime assay is more sensitive and is little impacted by the development of drug resistant mutation.

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.

Sequence conservation of the region targeted by the Abbott RealTime HBV viral load assay in clinical specimens

The Abbott RealTime HBV assay targets the N-terminal region of the S gene. Here we analyzed the sequence variability of the assay target region from >2,100 clinical specimens. Thermodynamic modeling of the percentage of bound primer/probe at the assay annealing temperature was performed to assess the potential effect of sequence variability.

Development of a new duplex real-time polymerase chain reaction assay for hepatitis B viral DNA detection

BACKGROUND

Quantification of hepatitis B virus (HBV) DNA can be used for diagnosing HBV infection and monitoring the effect of antiviral therapy. However, probably because of mismatches between the template and primer/probe, HBV DNA in some HBV infections could not be detected using currently available commercial assays with single primer/probe. By aligning the HBV sequences, we developed a duplex real-time polymerase chain reaction (PCR) assay using two sets of primers/probes and a specific armored DNA as internal control (IC).

RESULTS

The limit of the duplex real-time PCR assay was 29.5 IU/ml, whereas the specificity was 100%. The within-run precision coefficient of variation (CV) ranged from 1.02% to 2.73%, while the between-run CV ranged from 0.83% to 1.25%. The optimal concentration of armored DNA IC in the HBV DNA duplex real-time PCR assay was 1 000 copies/ml. Data from 69 serum samples with HBV infection showed that the performance of the duplex real-time PCR assay was comparable to that of the COBAS Ampliprep/Cobas Taqman (CAP/CTM) HBV assay and was superior to those of the domestic commercial HBV assays.

CONCLUSIONS

The duplex real-time PCR assay is sufficiently sensitive, specific, accurate, reproducible and cost-effective for the detection of HBV DNA. It is suitable for high throughput screening and frequent HBV DNA level monitoring.

Quantitation of hepatitis B virus DNA in plasma using a sensitive cost-effective "in-house" real-time PCR assay

BACKGROUND

Sensitive nucleic acid testing for the detection and accurate quantitation of hepatitis B virus (HBV) is necessary to reduce transmission through blood and blood products and for monitoring patients on antiviral therapy. The aim of this study is to standardize an "in-house" real-time HBV polymerase chain reaction (PCR) for accurate quantitation and screening of HBV.

MATERIALS AND METHODS

The "in-house" real-time assay was compared with a commercial assay using 30 chronically infected individuals and 70 blood donors who are negative for hepatitis B surface antigen, hepatitis C virus (HCV) antibody and human immunodeficiency virus (HIV) antibody. Further, 30 HBV-genotyped samples were tested to evaluate the "in-house" assay's capacity to detect genotypes prevalent among individuals attending this tertiary care hospital.

RESULTS

The lower limit of detection of this "in-house" HBV real-time PCR was assessed against the WHO international standard and found to be 50 IU/mL. The interassay and intra-assay coefficient of variation (CV) of this "in-house" assay ranged from 1.4% to 9.4% and 0.0% to 2.3%, respectively. Virus loads as estimated with this "in-house" HBV real-time assay correlated well with the commercial artus HBV RG PCR assay ( r = 0.95, P < 0.0001).

CONCLUSION

This assay can be used for the detection and accurate quantitation of HBV viral loads in plasma samples. This assay can be employed for the screening of blood donations and can potentially be adapted to a multiplex format for simultaneous detection of HBV, HIV and HCV to reduce the cost of testing in blood banks.

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.

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.