Accuracy Validation of the Elecsys HBsAg II Quant Assay and Its Utility in Resolving Equivocal Qualitative HBsAg Results.

Background and Objectives: There are reports of false qualitative HBsAg results, because of various causes, such as samples with low HBsAg concentrations that may produce false positives. The main aims of this study were to validate the analytical accuracy and to assess the utility of the Elecsys assay compared to that of the qualitative HbsAg assay as a screening test in resolving equivocal qualitative HbsAg results. Materials and Methods: The limit of blank (LoB), the limit of detection (LoD), the limit of quantification (LoQ), and linearity were estimated to validate the analytical accuracy of the Elecsys HBsAg II Quant assay. A total of 449 serum samples showing initial equivocal results (1-50 index) were evaluated by Elecsys HBsAg II Quant and ADVIA Centaur HBsAg II assays. Results: The LoQ of the assay was determined to be 0.050 IU/mL, as provided by the manufacturer. The Kappa agreement between the two assays was almost perfect, at 0.9669, despite seven discordant results. With a specificity of 100% at new cut-off index value ≥5.42, about 78 samples (17%, 78/449) with index value ≥5.42 were interpreted as positives without further duplicate tests, however the remaining 371 samples with index value <5.42 need to be confirmed with additional HBV marker assays. Conclusions: We confirm that the Elecsys HBsAg II Quant assay is accurate and sensitive for HBV infection and recommend it as an alternative confirmatory HBsAg assay for resolving equivocal qualitative HBsAg results.

Analytical Performance of the Sysmex HISCL HBsAg Assay and Comparison with the Roche Elecsys HBsAg II Quant Assay in the Quantification of Hepatitis B Surface Antigen.

Background and Objectives: This study aims to estimate the analytical performance of the Sysmex HISCL HBsAg assay and to assess the analytical correlation with the Roche Elecsys HBsAg II quant assay with clinical samples and the WHO International Standard (IS). Materials and Methods: The intra-assay precision, linearity, assay limitation, accuracy, and comparative evaluation of the HISCL HBsAg assay were estimated. Results: Extrapolating from the plot of the average total allowable error versus the reference value, an accuracy goal of 20% would be achieved around a limit of quantification (LoQ) of 0.014867 IU/mL. The percentage of biases for each level of the WHO IS measured by the two assays were less than 15%, except for the WHO 3rd IS, for which the HISCL HBsAg assay achieved a percentage of bias of 33%. In the comparative evaluation, Passing-Bablok regression analysis did not reveal any significant deviation from linearity between the two assays (y = -48.6998 + 1.9206x; p = 0.79 by the CUSUM test for linearity). The mean difference of the quantitative HBsAg level between the two assays was 1762.5 IU/mL in the Bland-Altman plot. Conclusions: The HISCL HBsAg assay, with a highly sensitive LoQ of 0.03 IU/mL, showed similar analytical performance in HBsAg quantification to the Elecsys HBsAg II quant assay and may be helpful in obtaining better diagnoses and therapeutic strategies for treating HBV infections.

[Recent advances in understanding and diagnosing hepatitis B virus infection]. / Progrès récents dans la compréhension et le diagnostic de l'infection chronique par le virus de l'hépatite B.

Hepatitis B virus (HBV) infects approximately 257 million individuals worldwide. Recent advances in the virology and diagnosis of HBV infection are summarized in this review article. A novel classification of the different phases of chronic HBV infection, proposed by the European Association for the Study of the Liver (EASL), is presented. New diagnostic and monitoring tools are now available, including rapid diagnostic tests for hepatitis B surface antigen (HBsAg) detection, HBsAg quantification assays, an HBV core-related antigen (HBcrAg) quantification test, and HBV RNA quantification testing. Their clinical utility under study is discussed in this review.

A randomized clinical trial of peginterferon alpha-2b with or without entecavir in patients with HBeAg-negative chronic hepatitis B: Role of host and viral factors associated with treatment response.

Combining peginterferon (PEG-IFN) and a potent nucleoside/nucleotide analogue might improve treatment response in patients with chronic hepatitis B (CHB). The aims of this study were to compare the efficacy of PEG-IFN alpha-2b with or without entecavir in HBeAg-negative CHB and to investigate predictors of response. A total of 126 treatment-naïve patients were randomly assigned to receive monotherapy (n = 63) or combination therapy (n = 63) for 48 weeks. Virological response (VR) was defined as HBV DNA level <2000 IU/mL at week 96. Baseline factors including polymorphisms in the IFNL3 (rs12979860) and HLA-DPA1 (rs3077) genes and on-treatment viral kinetics were determined. At week 48, rates of undetectable HBV DNA were lower in the monotherapy than combination groups, but rates of HBsAg clearance and decline were comparable. At week 96, there was no difference between the corresponding groups regarding virological response (41.3% vs 38.1%, P = 0.856), HBsAg clearance (9.5% vs 4.8%, P = 0.491) and HBsAg decline. Baseline HBsAg level [odds ratio (OR): 3.14 (1.34-7.69), P = 0.012] and rs3077 polymorphism [OR: 2.78 (1.27-6.11), P = 0.011] were independent predictors of response. Patients carried GG genotype of rs3077 with low baseline HBV (<1000 IU/mL) had high probability of achieving VR (76.5%) and HBsAg clearance (29.4%). None of the patients without decrease in HBsAg combined with <2 log10 HBV DNA decline at week 12 achieved a virological response. In conclusion, the combination therapy lead to greater on-treatment HBV DNA suppression but did not improve virological response and HBsAg clearance/decline over monotherapy. Host and viral factors could help optimize decision-making at baseline and during PEG-IFN-based therapy.

Serum hepatitis B core-related antigen as a treatment predictor of pegylated interferon in patients with HBeAg-positive chronic hepatitis B.

BACKGROUND & AIMS: The role of quantitative serum hepatitis B core-related antigen (HBcrAg) in patients with chronic hepatitis B (CHB) receiving pegylated interferon (PEG-IFN) is unclear. This study was aimed at comparing its usefulness with quantitative HBsAg in patients with HBeAg-positive CHB receiving PEG-IFN therapy. METHODS: A total 46 patients treated with PEG-IFN for 48 weeks were retrospectively analysed. Intrahepatic covalently closed circular DNA (cccDNA) from paired liver biopsies and serial serum HBsAg and HBcrAg during therapy were assessed. RESULTS: Virological response (VR), defined as HBeAg clearance and HBV DNA <2000 IU/ml at 24 weeks post treatment, was achieved in 15 (32.6%) patients. Responders had significantly higher cccDNA decline from baseline compared with non-responders. Baseline HBsAg and HBcrAg were correlated with cccDNA (r = 0.424, P = 0.020 and r = 0.564, P = 0.001, respectively), and changes in the corresponding markers during therapy were correlated with cccDNA reduction (r = 0.579, P = 0.001 and r = 0.503, P = 0.005, respectively). Responders showed more rapid decline of both markers during therapy compared with non-responders. In multivariate analysis, serum HBcrAg at week 12 was identified as a predictor of VR. The optimal cut-off value for HBcrAg (log10 8.0 U/ml) provided negative predictive value (NPV) of achieving VR at weeks 12 and 24 of 94.4 and 100%, respectively, while using HBsAg > 20 000 IU/ml provided NPV of 80 and 100% respectively. CONCLUSIONS: The convenient quantitative HBcrAg represented a reliable marker of intrahepatic cccDNA. Monitoring HBcrAg levels during PEG-IFN therapy may help identify patients with a very low probability of response comparable to, if not better than, quantitative HBsAg.

Hepatitis B surface antigen quantification as a predictor of seroclearance during treatment in HIV-hepatitis B virus coinfected patients from Sub-Saharan Africa.

BACKGROUND AND AIM: In Sub-Saharan Africa, seroclearance of hepatitis B surface antigen (HBsAg) and hepatitis B "e" antigen (HBeAg), including their quantifiable markers, have rarely been evaluated during long-term antiviral treatment among patients coinfected with HIV and hepatitis B virus (HBV). METHODS: In this prospective cohort study from two randomized-control trials in Côte d'Ivoire, 161 antiretroviral-naïve HIV-HBV coinfected patients starting lamivudine (n = 76) or tenofovir/emtricitabine (n = 85) containing antiretroviral therapy were included. HBV DNA was quantified using an in-house assay (detection limit = 12 copies/mL) and HBsAg quantification (qHBsAg) using the Elecsys assay. RESULTS: Overall, 33 (20.5%) patients were HBeAg positive, 121 (75.2%) had detectable HBV DNA, and 92/93 (98.9%) harbored HBV genotype E. Median treatment duration was 35.5 months (interquartile range: 24.3-36.4). Among HBeAg-positive patients, cumulative proportion with HBeAg seroclearance was 46.3% (n = 14). Overall, cumulative proportion of HBsAg seroclearance was 6.6% (n = 10). Lower baseline qHBsAg levels and strong 12-month declines in qHBsAg were significantly associated with HBsAg seroclearance for both HBeAg-negative and HBeAg-positive patients. When taken at certain levels, these determinants provided moderate sensitivity (Se) and specificity (Sp) in predicting HBsAg seroclearance at month 36 (≤ 1000 IU/mL at baseline, Se = 0.80, Sp = 0.80; ≥ 1.0 log10 IU/mL drop at month 12, Se = 0.57, Sp = 1.00). Instead, qHBsAg levels ≤ 100 or ≤ 10 IU/mL at month 12 were optimal (both Se = 0.90 and Sp = 1.00). Detectable HBV-DNA provided fairly high Se and Sp when evaluated at baseline (Se = 1.00, Sp = 0.80), but not at month 12 (Se = 0.80, Sp = 0.40). CONCLUSIONS: HBsAg seroclearance rates are not common in patients from Sub-Saharan Africa treated with anti-HBV containing antiretroviral therapy. qHBsAg levels at 12 months of treatment may accurately predict HBsAg seroclearance.

On-treatment prediction of sustained response to peginterferon alfa-2a for HBeAg-negative chronic hepatitis B patients.

BACKGROUND & AIMS: We assessed predictors of response in HBeAg-negative chronic hepatitis B patients treated with peginterferon alfa-2a in routine clinical practice. METHODS: Ninety-five HBeAg-negative patients received peginterferonalfa-2a for 48 weeks and were followed-up for 48 weeks post-treatment. Serum HBsAg and HBV DNA levels were monitored during and after therapy with valid commercial assays. Sustained response (SR) was defined as HBV DNA <2000 IU/ml at study week 96. RESULTS: Twenty-two patients (23%) achieved SR and nine (9.5%) lost HBsAg. HBsAg decline was more profound in patients with SR. HBsAg decline ≥10% from baseline to week 24 was significantly associated with SR [81% (17/21) vs 37% (21/57); Odds ratio: 7.286 (2.162-24.552), P = 0.001]. The PARC rule (no decrease in HBsAg and <2 log drop in HBV DNA at week 12) was evaluated in a subset of 47 patients. Among eight patients who fulfilled the PARC rule, none achieved SR. Of the 39 patients who did not fulfil the PARC rule, 24 (62%) had HBsAg decline of ≥10% at week 24 (12 achieved SR) and 15 (38%) had HBsAg decline of <10% (1 achieved SR; negative predictive value: 93%). CONCLUSIONS: In HBeAg-negative chronic hepatitis B patients treated with peginterferon alfa-2a, HBsAg decline >10% at 24 weeks is significantly associated with SR. The combination of the PARC rule and week 24 decline in HBsAg can identify almost two-thirds of patients who are unlikely to achieve SR. Clinicaltrials.gov identifier: NCT01283074.

Viral determinants predicting hepatitis B surface antigen (HBsAg) seroclearance in HIV-/HBV-coinfected patients.

The aim of this retrospective study was the identification of clinically useful viral determinants for the prediction of hepatitis B surface antigen (HBsAg) seroclearance and sustained virological response in hepatitis B virus/human immunodeficiency virus (HBV-/HIV)-coinfected patients receiving HBV-active combined antiretroviral therapy (cART). Quantification of HBsAg, HBeAg and HBV DNA before and after initiation of HBV-active cART in a cohort of 59 HIV-/HBV-coinfected patients was performed. Calculations of receiver operating characteristics (ROC) and Kaplan-Meier analysis were used for the identification of predictors of HBsAg seroclearance for HBeAg-positive [HBeAg(+); n = 36] and HBeAg-negative [HBeAg(-);n = 23] patients. HBeAg(+) patients with an HBsAg on-treatment decline ≥ 1 log IU/mL per year achieved higher HBsAg loss rates (P = 0.0294), whereas the quantification of HBeAg had no predictive value for HBsAg seroclearance. Among HBeAg(-) patients, a pretreatment baseline cut-off level of HBsAg ≤ 100 IU/mL was highly predictive for HBsAg seroclearance. No significant influence of the HBV genotype on HBsAg seroclearance was observed among the entire cohort. Quantitative determination of HBsAg provides a clinically useful viral parameter for the prediction of HBsAg seroclearance both in HBeAg(+) and HBeAg(-) HIV-/HBV-coinfected patients receiving HBV-active cART.

Response to peginterferon alfa-2a (40KD) in HBeAg-negative CHB: on-treatment kinetics of HBsAg serum levels vary by HBV genotype.

BACKGROUND & AIMS: We investigated whether HBV genotype influences on-treatment HBsAg kinetics and/or the end-of-treatment HBsAg levels associated with long-term virological response in HBeAg-negative chronic hepatitis B patients treated with peginterferon alfa-2a±lamivudine in the Phase III trial. METHODS: All patients (n=230) who participated in long-term follow-up were included according to the availability of HBsAg level measurements. Long-term virological response was defined as HBV DNA ≤ 10,000cp/ml (1786IU/ml) at 5 years post-treatment. Genotype-specific end-of-treatment HBsAg levels associated with long-term virological response (identified by ROC analysis) were assessed in 199 patients with HBsAg measurements available at baseline and end-of-treatment. HBsAg kinetics according to genotype and long-term virological response were investigated in the 117 patients with additional samples available at weeks 12, 24, and 72. RESULTS: Baseline HBsAg levels were significantly higher for A than B, C, and D genotypes (p<0.05). On-treatment HBsAg kinetics varied according to HBV genotype. The difference between responders and non-responders was greatest for genotype A from weeks 12-24; for genotypes B and D from baseline to week 12; there was no significant difference over any timeframe for genotype C. High positive predictive values for long-term virological response could be obtained by applying end-of-treatment genotype-specific cut-offs: 75%, 47%, 71%, and 75% for genotypes A (<400IU/ml), B (<50IU/ml), C (<75IU/ml), and D (<1000IU/ml), respectively. CONCLUSIONS: On-treatment HBsAg kinetics vary between HBV genotypes. Genotype-specific monitoring timeframes and end-of-treatment thresholds could ameliorate response-guided treatment of HBeAg-negative chronic hepatitis B.

Detection and quantitation of hepatitis B surface antigen (HBsAg) on dried blood spots: a solution for easy access for hepatitis B diagnosis and elimination in remote areas.

Hepatitis B virus (HBV) is generally endemic in resource-limited countries, which are characterized by a deficit of technical facilities that could delay diagnosis and treatment. To facilitate the accessibility to diagnostic and connection to treatment, evaluation, and promotion of alternatives and/or simplified strategies and inexpensive tools such as dried blood specimens need to be investigated and implemented. This study aimed to evaluate dried blood spots (DBS) for the detection and quantification of HBsAg. This study included 100 DBS from subjects tested positive for HBsAg, and 50 DBSs from subjects tested negative for HBsAg by the automate Architect i1000sr (Abbott Diagnostics, Ireland). Hepatitis B surface antigen detection was performed with determine HBsAg Alere® tests (Alere International Limited, Ireland) and Architect® HBsAg Qualitative II Assays (Abbott, Diagnostics, Ireland) after 15 and 30 days (D15, D30). For HBsAg-positive subjects, the quantification of HBsAg was performed at day zero (D0) from plasma and at D15 and D30 from the DBSs. At D15, the sensitivity and specificity were 96% and 100% for the Determine® tests and 100% and 100% for the Architect® tests, respectively. At D30, the sensitivity and specificity were 96% and 100% for the Determine® tests and 100% and 100% for the Architect® tests, respectively. For HBsAg quantification, the agreement rates were 96%, 96% and 100% between D0-D15, D0-D30 and D15-D30, respectively. This work showed that DBSs can be very useful for HBsAg detection and quantification and therefore in the management of HBV infection in resource-limited settings.

Inter-method variability of hepatitis B surface antigen quantification in a cohort of Egyptian patients with chronic hepatitis B virus.

BACKGROUND AND STUDY AIMS: Hepatitis B (HB) surface antigen (HBsAg) levels can predict clinical and treatment outcomes in chronic HB virus (HBV) infection. We aimed to compare the performance of two different assays [Elecsys® (Roche) and Architect™ (Abbott)] for HBsAg quantification and evaluate HBsAg levels in the various immune phases in a cohort of Egyptian patients with chronic HBV. PATIENTS AND METHODS: Quantitative HBsAg by Elecsys® and Architect™ assays, measurement of routine biochemical and serological markers, and transient elastography were performed in 92 patients with chronic HBV. Results of the two assays and other tests were compared. RESULTS: Ninety-two treatment-naive patients with chronic HBV, (70% males; mean age, 36.1 ± 10.5 years) were recruited from Cairo Fatemic Hospital. Patients were categorized as HBeAg positive (n = 22) and HBeAg negative (n = 70). The Architect™ and Elecsys® assays were significantly correlated (intraclass correlation coefficient: 0.913; 95% CI: 0.870-0.943; p < 0.001). However, Deming regression, Passing and Bablok, and Bland-Altman statistical analyses showed discordance among the assays. HBsAg levels by both assays were significantly higher in the HBeAg positive than patients with HBeAg-negative (p = 0.033 and 0.013, respectively). HBsAg levels in the Architect™ and Elecsys® assays were significantly higher in HBeAg-negative chronic hepatitis than in HBeAg-negative chronic infection (p = 0.002 and 0.004, respectively) CONCLUSION: Both assays for qHBsAg were found to be simple and reproducible tests that could classify patients and provide additional evidence on the natural history of HBV.

Performance of HBsAg quantification assays for detection of Hepatitis B virus genotypes and diagnostic escape-variants in clinical samples.

BACKGROUND: The impact of hepatitis B virus (HBV) genomic variability on the measurement of HBsAg level has been poorly evaluated. OBJECTIVE: This study was designed to compare the performance of all the available assays measuring HBsAg level in this setting. STUDY DESIGN: A large selection of wild type HBV genotypes (n=184) and HBsAg strains harboring mutations in the S gene (n=81) from clinical samples was studied with three HBsAg quantification assays: Architect HBsAg (Abbott), LiaisonXL Murex HBsAg Quant (DiaSorin) and the Elecsys HBsAgII (Roche). RESULTS: The overall percentage of positive results was 99.2% for Abbott, 98.9% for DiaSorin and 98.1% for Roche. Abbott and Roche assays provided an excellent concordance in HBsAg quantification (global mean bias of -0.006 logIU/mL). By contrast, DiaSorin underestimated HBsAg level with values 0.112 logIU/ml and 0.103 logIU/ml lower than Abbott and Roche, respectively. By contrast, DiaSorin slightly over quantified gtC (2.5% over the expected value) while Abbott provided values 6.2% lower than expected and 16.2% lower than what observed for the other genotypes. HBsAg quantitative assays were influenced by HBs protein substitutions irrespective to the genotype but no specific protein pattern that would particularly impair the quantification by one technique has been identified. However, Roche seemed to be particularly impacted by substitutions at 145 residue: 75% of under quantified samples carried a substituted 145 residue. CONCLUSION: This head-to-head comparison indicates a good correlation between all current systems used to quantify HBsAg but clearly shows an influence of both the genotype and the presence of "a" determinant variants in the absolute quantification of HBsAg. While these discrepancies may not translate into major clinical consequence, they may explain an absence of detection of weak concentration of HBsAg on some systems.

Coexistence of circulating HBsAg and anti-HBs antibodies in chronic hepatitis B carriers is not a simple analytical artifact and does not influence HBsAg quantification.

BACKGROUND: Presence at the same time of HBsAg and anti-HBs antibodies (HBsAg/Ab) is an entity sometimes encountered in chronic hepatitis B (CHB) carriers. OBJECTIVES: This study was designed to characterize such serological profiles and to assess the reliability of serological marker quantification by three commercially available assays in this setting. STUDY DESIGN: Among 2578 CHB identified patients, 129 (5%) had an HBsAg/Ab profile as determined by Abbott Architect. After exclusion of co-infections (HIV, HCV, HDV), HBV reactivation or HBIg treatment, 101 samples from 62 patients were tested for HBsAg and anti-HBs quantification using Architect, DiaSorin Liaison-XL and Roche Modular-Cobas. Influence of genotype and HBsAg variants was studied in 31 samples with HBV replication. RESULTS: HBsAg detection was confirmed with the 3 techniques for 98% (n = 99) of the samples while the HBsAg/Ab profile was concordant between all techniques for 65% of them. The overall correlation between the 3 HBsAg quantification techniques was good (R(2): 0.94-0.97). The median HBsAg concentration was comparable for the 99 samples whatever the used technique but a bias of -0.11 and 0.02 log IU/mL were noticed for DiaSorin and Roche compared to Abbott, respectively. Anti-HBs quantifications were poorly correlated between techniques with major discrepancies observed. Genotype and substitutions within the "a" determinant showed an impact on HBsAg quantification. CONCLUSIONS: The double HBsAg/Ab profile is not an analytical artifact and is confirmed on all commercially available techniques. While such profile does not influence HBsAg quantification, differences of HBsAg quantification were noticed according to HBV genotype or HBsAg variant.

HBsAg Level as Predictor of Liver Fibrosis in HBeAg Positive Patients With Chronic Hepatitis B Virus Infection.

BACKGROUND AND AIMS: Preliminary data suggests lower serum hepatitis B surface antigen level is associated with more severe liver fibrosis in HBeAg positive patients. We evaluated the association of HBsAg level with biochemical, virological, and histological features in asymptomatic patients with chronic HBV infection. METHODS: HBsAg levels were measured at baseline in 481 asymptomatic, treatment naive patients with chronic HBV infection. Subjects were followed-up prospectively (median, 12; range, 8-36 months). Phases of HBV infection were defined after regular monitoring of HBV-DNA and transaminases. Liver histology was scored using the METAVIR system. RESULTS: HBeAg positive (n, 126) patients were significantly younger than HBeAg negative (n, 355), median age 26 vs 30 years; P < 0.01. HBV genotype could be determined in 350 patients, 240 (68.57%) had genotype D and 100 (28.57%) had genotype A. HBsAg level had modest correlation with serum HBV DNA(r = 0.6 vs 0.4 in eAg positive & negative respectively). HBeAg + ve patients with fibrosis score ≥ F2 showed significantly lower median serum HBsAg levels and serum HBV DNA levels compared with patients with F0-F1 score (median, range; 4.51, 2.99-6.10 vs 5.06, 4.13-5.89, P < 0.01) and (8.39, 3.85-10.60, P < 0.01) respectively. Significant inverse correlation of HBsAg level was found with liver fibrosis in eAg positive group (r = -0.76; P < 0.001). HBsAg level cut off value 4.7 log10 IU/ml predicted moderate to advance fibrosis (F ≥ 2) with 92% sensitivity, 85% specificity & 91% negative predictive value. CONCLUSION: Lower HBsAg level might reflect the status of advanced liver fibrosis in HBeAg positive chronic hepatitis B subjects.

Clinical performance of the novel DiaSorin LIAISON(®) XL murex: HBsAg Quant, HCV-Ab, HIV-Ab/Ag assays.

BACKGROUND: The fully automated and closed LIAISON(®)XL platform was developed for reliable detection of infection markers like hepatitis B virus (HBV) surface antigen (HBsAg), hepatitis C virus (HCV) antibodies (Ab) or human immunodeficiency virus (HIV)-Ag/Ab. To date, less is known about the diagnostic performance of this system in direct comparison to the common Abbott ARCHITECT(®) platform. OBJECTIVES: We compared the diagnostic performance and usability of the DiaSorin LIAISON(®)XL with the commonly used Abbott ARCHITECT(®) system. STUDY DESIGN: The qualitative performance of the above mentioned assays was compared in about 500 sera. Quantitative tests were performed for HBsAg-positive samples from patients under therapy (n=289) and in vitro expressed mutants (n=37). For HCV-Ab, a total number of 155 selected samples from patients chronically infected with different HCV genotypes were tested. RESULTS: The concordance between both systems was 99.4% for HBsAg, 98.81% for HCV-Ab, and 99.6% for HIV-Ab/Ag. The quantitative LIAISON(®)XL murex HBsAg assay detected all mutants in comparable amounts to the HBsAg wild type and yielded highly reliable HBsAg kinetics in patients treated with antiviral drugs. Dilution experiments using the 2nd International Standard for HBsAg (WHO) showed a high accuracy of this test. HCV-Ab from patients infected with genotypes 1-3 were equally detected in both systems. Interestingly, S/CO levels of HCV-Ab from patients infected with genotype 3 seem to be relatively low using both systems. CONCLUSIONS: The LIAISON(®)XL platform proved to be an excellent system for diagnostics of HBV, HCV, and HIV with equal performance compared to the ARCHITECT(®) system.

HBsAg Quantification in Clinical Practice.

Several standardized commercial assays for quantification of hepatitis B surface antigen (qHBsAg) are now available. Studies on HBsAg kinetics from Asia and Europe have demonstrated that HBsAg levels are highest during the immune-tolerant phase, become lower during immune-clearance phase and are the lowest in hepatitis B 'e' antigen (HBeAg)-negative inactive low-replicative phase with a rise during HBeAg-negative chronic hepatitis B (CHB). Combined use of hepatitis B virus-deoxyribonucleic acid (HBV-DNA) and HBsAg levels may help in differentiating true inactive carrier state from HBeAg-negative CHB. Several retrospective studies have demonstrated a role for decline in HBsAg level for predicting response and nonresponse to therapy. In HBeAg-positive patients treated with pegylated-interferon (PEG-IFN), a lack of decline of qHBsAg at week 12 predicts nonresponders while a decline of qHBsAg at week 24 predicts responders to PEG-IFN. In HBeAg-negative patients, if at week 12, there is no decline in qHBsAg and the HBV-DNA decline is < 2 log, the patient is unlikely to respond, then stopping of PEG-IFN should be considered. With nucleos(t)ide analogs, the decline in HBsAg is lower than that with PEG-IFN and more marked in patients with HBeAg-positive chronic hepatitis, with elevated alanine aminotransaminase (ALT), thus suggesting that active immune response against HBV is required to lower HBsAg. In patients with HBeAg-negative chronic hepatitis, fall in HBsAg may help in developing stopping rules to reduce the need for lifelong therapy. Information provided by HBsAg is complementary to HBV-DNA and cannot replace the same. Prospective studies on HBsAg kinetics from all regions of the world are required to define optimum time of testing and cutoff levels before stopping rules can be recommended.