Quantitative hepatitis B surface antigen and hepatitis B e antigen titers in prediction of treatment response to entecavir†
Article first published online: 22 APR 2011
Copyright © 2011 American Association for the Study of Liver Diseases
Volume 53, Issue 5, pages 1486–1493, May 2011
How to Cite
Lee, J. M., Ahn, S. H., Kim, H. S., Park, H., Chang, H. Y., Kim, D. Y., Hwang, S. G., Rim, K. S., Chon, C. Y., Han, K.-H. and Park, J. Y. (2011), Quantitative hepatitis B surface antigen and hepatitis B e antigen titers in prediction of treatment response to entecavir. Hepatology, 53: 1486–1493. doi: 10.1002/hep.24221
Potential conflict of interest: Nothing to report.
- Issue published online: 22 APR 2011
- Article first published online: 22 APR 2011
- Accepted manuscript online: 10 FEB 2011 11:30AM EST
- Manuscript Accepted: 22 JAN 2011
- Manuscript Received: 10 MAY 2010
- Bilateral International Collaborative R&D Program (Ministry of Knowledge Economy, South Korea) and the Good Health R&D Project (Ministry of Health, Welfare, and Family Affairs, South Korea). Grant Number: A050021
Quantitative hepatitis B surface antigen (qHBsAg) and quantitative hepatitis B e antigen (qHBeAg) titers are emerging as useful tools for measuring viral loads and for predicting the virological response (VR) and serological response (SR) to pegylated interferon therapy. However, the clinical utility of these assays in patients taking entecavir (ETV) is largely unknown. Treatment-naive patients with chronic hepatitis B (CHB) who were taking ETV for 2 years were enrolled. The qHBsAg and qHBeAg levels were serially measured with the Architect assay. From 95 patients, 60.0% of whom were hepatitis B e antigen–positive [HBeAg(+)], 475 samples were analyzed. The median baseline log hepatitis B virus (HBV) DNA, log qHBsAg, and log qHBeAg values were 6.73 copies/mL (4.04-9.11 copies/mL), 3.58 IU/mL (1.17-5.10 IU/mL), and 1.71 Paul Ehrlich (PE) IU/mL (−0.64 to 2.63 PE IU/mL), respectively. For the prediction of VR (HBV DNA < 60 copies/mL at 24 months) in HBeAg(+) patients, baseline alanine aminotransferase (P = 0.013), HBV DNA (P = 0.040), and qHBsAg levels (P = 0.033) were significant. For the prediction of VR, the area under the curve for the baseline log qHBsAg level was 0.823 (P < 0.001); a cutoff level of 3.98 IU/mL (9550 IU/mL on a nonlogarithmic scale) yielded the highest predictive value with a sensitivity of 86.8% and a specificity of 78.9%. As for SR (HBeAg loss at 24 months), the reduction of qHBeAg was significantly greater in the SR(+) group versus the SR(−) group. The sensitivity and specificity were 75.0% and 89.8%, respectively, with a decline of 1.00 PE IU/mL at 6 months. With ETV therapy, the correlation between HBV DNA and qHBsAg peaked at 6 months in HBeAg(+) patients. Conclusion: Both qHBsAg and qHBeAg decreased significantly with ETV therapy. The baseline qHBsAg levels and the on-treatment decline of qHBeAg in HBeAg(+) patients were proven to be highly useful in predicting VR and SR, respectively. The determination of qHBsAg and qHBeAg can help us to select the appropriate strategy for the management of patients with CHB. However, the dynamic interplay between qHBsAg, qHBeAg, and HBV DNA during antiviral therapy remains to be elucidated. (Hepatology 2011;)
Chronic infection with hepatitis B virus (HBV) is a worldwide health problem, with more than 400 million people thought to be infected. Moreover, these patients are at increased risk for disease progression to cirrhosis and hepatocellular carcinoma.1 Large cohort studies have shown that elevated levels of HBV DNA are closely associated with the development of cirrhosis and hepatocellular carcinoma, and reducing HBV DNA to undetectable levels is one of the primary goals in patients receiving antiviral therapy.2, 3
The current gold standard in monitoring viral loads is real-time polymerase chain reaction (PCR), which offers high sensitivity and accuracy.4 Data from these assays reflect the disease status and are employed by most clinical studies.2, 3 The shortcomings of PCR, however, are its relatively high cost and unavailability in some areas. Moreover, viral activity can still be monitored in patients with undetectable HBV DNA through the measurement of hepatitis B surface antigen (HBsAg) and/or hepatitis B e antigen (HBeAg) titers.
HBsAg has long served as a qualitative serological marker for the diagnosis of HBV. Recent advances in the development of HBsAg assays with a quantitative, analytical approach have led to the exploration of its potential role in monitoring disease and therapy outcome. Since 2004, when Deguchi et al.5 determined Pearson's correlation coefficient (r) between the quantitative hepatitis B surface antigen (qHBsAg) titer and the serum HBV DNA level to be 0.862, the field of qHBsAg research has been active. Specifically, qHBsAg has shown to be correlated with intrahepatic covalently closed circular DNA (cccDNA),6, 7 and subsequent studies have lent further support to a correlation between qHBsAg and serum HBV DNA levels.8, 9 To date, the potential role of qHBsAg in antiviral therapy monitoring has been studied largely in patients receiving pegylated interferon (PEG-IFN).10-12 Moucari et al.13 reported that an early drop in qHBsAg was highly predictive of a sustained virological response (SVR) in HBeAg(−) patients. This was similar to the results obtained by Brunetto et al.,14 who found that an on-treatment decline of qHBsAg was significantly associated with sustained HBsAg clearance.
In contrast to studies of PEG-IFN, there is a relative paucity of data concerning qHBsAg levels in patients receiving oral nucleos(t)ide analogues. The effects of adefovir and lamivudine (LAM) on qHBsAg have been analyzed in several studies; the potency of these agents in decreasing qHBsAg levels was low.4, 6, 9 Among patients taking entecavir (ETV), which is a potent and preferred first-line agent, little is known about qHBsAg; in two studies, the clinical utility of qHBsAg was not demonstrated.15, 16
The quantitative hepatitis B e antigen (qHBeAg) titer has been introduced and evaluated as a surrogate marker of on-treatment response. In patients receiving conventional interferon, PEG-IFN, or LAM, a decrease in qHBeAg levels during antiviral therapy might have predictive value in determining the clinical course and the occurrence of viral breakthrough.17-21 However, no study exploring qHBeAg changes in patients receiving ETV therapy has yet been conducted.
Recent investigations of qHBsAg have suggested its potential for wider applications encompassing the natural course of HBV.22, 23 These studies have demonstrated significant differences in qHBsAg across the different phases of HBV infection over a long time period. Moreover, Thompson et al.24 reported differences in the correlations between qHBsAg and HBV DNA in HBeAg(+) patients and HBeAg(−) patients in conjunction with qHBeAg. Their results have provided new insights into viral pathogenesis. However, temporal data describing in detail the correlation between qHBsAg/qHBeAg and HBV DNA in patients treated with antivirals have yet to be published.
In this study, we systematically analyzed the profiles of serial qHBsAg as well as qHBeAg in patients receiving ETV, and we investigated the clinical utility of these quantitative serological markers. Here we provide additional temporal information on the correlation between qHBsAg and HBV DNA as part of a broader attempt to elucidate their dynamic relationship during antiviral therapy.
Patients and Methods
Study Design and Patients.
We enrolled all patients with chronic hepatitis B (CHB) at Severance Hospital (Seoul, South Korea) or CHA Bundang Medical Center (Seongnam-Si, South Korea) who were started on ETV (0.5 mg once a day) between January 2007 and June 2008 and for whom stored serum was available. The inclusion criteria were the presence of serum HBsAg for 6 or more months, HBV genotype C, an age greater than 16 years, and a previous lack of treatment with a subsequent ETV treatment period of at least 24 months. ETV was commenced when the HBV DNA level was more than 10,000 copies/mL and when either the alanine aminotransferase (ALT) level was greater than 2 times the upper limit of normal or biopsy showed significant fibrosis/cirrhosis.25 The exclusion criteria were a coinfection with hepatitis C virus or human immunodeficiency virus, a history of organ transplantation, decompensated liver cirrhosis (ascites, varices, encephalopathy, albumin level < 3 mg/dL, total bilirubin level > 2.5 mg/dL, or prothrombin time > 3 seconds longer than normal), and a concurrent use of immunomodulatory drugs or corticosteroids. Written, informed consent was obtained from all participating patients. This study was approved by the local institutional review board and was conducted in accordance with the principles set forth in the Declaration of Helsinki.
Routine biochemical tests, including ALT, albumin, total bilirubin, and creatinine levels, were performed with a sequential multiple autoanalyzer.
The Architect HBsAg QT immunoassay (Abbott Diagnostic, Wiesbaden, Germany) was used to quantify qHBsAg according to the manufacturer's instructions.5, 13 Briefly, the assay was carried out in two steps: HBsAg present in the sample was bound to antibody to hepatitis B surface antigen (anti-HBs)–coated microparticles, and an acridinium-labeled anti-HBs conjugate was added together with pretrigger and trigger solutions. The products of the resulting chemiluminescent reaction were measured in relative light units. The qHBsAg calibration curve ranged from 0.05 to 250 IU/mL, and the samples were diluted with a diluent (1:20 or 1:250) as needed to expand the detection range.
The Architect platform (Abbott Diagnostic) was also used to quantify qHBeAg. Briefly, qHBeAg was measured with an automated microparticle chemiluminescent immunoassay based on a previously described method.18, 21, 24 Although this commercial HBeAg kit is not marketed as a quantitative assay, it produces a signal-to-cutoff ratio that is linear within a restricted range. The HBeAg reference preparation, which had a defined HBeAg activity of 100 Paul Ehrlich (PE) IU/mL, was obtained from the Paul Ehrlich Institute (Langen, Germany). An in-house working HBeAg standard was then prepared from a pool of high-titer HBeAg(+) specimens and was calibrated against the PE reference preparation; dilution was performed as needed. The linear range was approximately 0.13 to 100 PE IU/mL. A standard curve was generated, and linear regression was used to convert the assay results into the appropriate units (PE IU/mL) for each sample. For samples that fell outside the linear range of the assay, serial dilutions were performed with the Architect HBsAg manual diluent.
Serum levels of HBV DNA were quantified with a real-time PCR assay on a Cobas TaqMan 48 analyzer (Roche Molecular Systems, Branchburg, NJ); the lower detection limit was 60 copies/mL. All laboratory assays were performed every 6 months. When genotypic resistance to ETV was suspected, it was analyzed with the method of restriction fragment mass polymorphism.26
Endpoints and Definitions.
The primary endpoint of this study was the serial analysis of qHBsAg and qHBeAg profiles in patients receiving ETV. The secondary endpoints included the evaluation of the clinical utility of these titers in predicting virological response (VR) and serological response (SR) in HBeAg(+) patients. In addition, the temporal relation during ETV therapy between qHBsAg and HBV DNA according to the HBeAg status (in terms of correlation coefficients) was investigated.
VR was defined as an HBV DNA level undetectable by a real-time PCR assay (<60 copies/mL) at 24 months. SR was defined as a loss of HBeAg at 24 months in HBeAg(+) patients. Virological breakthrough was defined as an increase in HBV DNA levels to ≥1 log copies/mL from the treatment nadir after a decline of ≥2 log copies/mL. Primary nonresponse was defined as an HBV DNA decline of <2 log copies/mL after 6 months of therapy.
To summarize the continuous variables, we used medians and ranges or means and standard deviations (SDs). The chi-square test or Fisher's exact test and the Student t test or paired-samples test were used to compare the categorical and continuous variables, respectively. Multivariate analysis was carried out with a stepwise logistic regression model. To determine the best cutoff for maximal accuracy, we applied receiver operating characteristic (ROC) curves and areas under the curve (AUCs). The correlation between variables was analyzed with r. A P value less than 0.05 was considered to be statistically significant. SPSS version 17.0 (SPSS, Inc., Chicago, IL) was the software used for all statistical analyses.
Ninety-five patients were enrolled, and 475 serial samples were analyzed. The baseline characteristics of the patients were as follows: the median age was 48 years (22-72 years), 68 patients (71.6%) were male, and 57 patients (60.0%) were HBeAg(+). The median baseline values of ALT, log HBV DNA, log qHBsAg, and log qHBeAg were 66 IU/L (20-325 IU/L), 6.73 copies/mL (4.04-9.11 copies/mL), 3.58 IU/L (1.17-5.10 IU/L), and 1.71 PE IU/mL (−0.64 to 2.63 PE IU/mL), respectively (Table 1).
|Characteristic||HBeAg(+) (n = 57)||HBeAg(−) (n = 38)|
|Age, years [median (range)]||46 (22-69)||49 (36-72)|
|Male sex [n (%)]||39 (68.4)||29 (76.3)|
|ALT, IU/L [median (range)]*||63 (21-325)||71 (20-311)|
|HBV DNA, log copies/mL [median (range)]||7.15 (4.04-9.11)||6.25 (4.69-8.74)|
|qHBsAg, log IU/mL [median (range)]||3.69 (1.17-5.10)||3.45 (2.28-4.70)|
|qHBeAg, log PE IU/mL [median (range)]||1.71 (−0.64 to 2.63)||—|
Antiviral Response to ETV Therapy.
At 12 and 24 months, VR was achieved in 29 (50.9%) and 38 patients (66.7%) in the HBeAg(+) group and in 33 (86.8%) and 36 patients (94.7%) in the HBeAg(−) group, respectively. Four (7.0%) and five patients (8.8%) achieved HBeAg seroconversion at 12 and 24 months, respectively, and three additional patients (5.3%) achieved HBeAg seroclearance through month 24. ALT normalization was observed in 58 patients (90.6%) at 12 months and in 60 patients (93.8%) at 24 months from a total of 64 patients who had elevated baseline ALT levels. No patient had HBsAg clearance through month 24. One patient (1.1%) was distinguished by primary nonresponse, and no patient had a biochemical or virological breakthrough during the study period.
Serial Values of qHBsAg.
Overall, log qHBsAg decreased significantly from 3.73 ± 0.74 (baseline) to 3.49 ± 0.58 IU/mL (P = 0.002) at 24 months in HBeAg(+) patients and from 3.42 ± 0.49 (baseline) to 3.21 ± 0.51 IU/mL (P = 0.005) at 24 months in HBeAg(−) patients, and there were significant differences between HBeAg(+) and HBeAg(−) patients (P < 0.05). When log qHBsAg was evaluated according to the VR status, it gradually declined among HBeAg(+) patients from 3.48 ± 0.65 to 3.33 ± 0.55 IU/mL (P = 0.097) in the VR(+) group and from 4.22 ± 0.68 to 3.80 ± 0.54 IU/mL (P = 0.005) in the VR(−) group (Fig. 1A). Similarly, among HBeAg(−) patients, log qHBsAg decreased from 3.40 ± 0.48 to 3.20 ± 0.50 IU/mL (P = 0.007) in the VR(+) group and from 3.77 ± 0.73 to 3.60 ± 0.75 IU/mL (P = 0.058) in the VR(−) group (Fig. 1B). Among HBeAg(+) patients, significant differences in qHBsAg levels were seen between the VR(+) and VR(−) groups (P < 0.005).
Serial Values of qHBeAg.
In 57 HBeAg(+) patients, log qHBeAg decreased significantly from 1.45 ± 1.03 (baseline) to 0.42 ± 1.00 PE IU/mL (P < 0.001) at 24 months. When log qHBeAg was evaluated according to the VR status, it declined from 1.11 ± 1.04 to −0.01 ± 0.71 PE IU/mL (P < 0.001) in the VR(+) group and from 2.11 ± 0.65 to 1.26 ± 0.95 PE IU/mL (P < 0.001) in the VR(−) group (Fig. 2A). There were significant differences in qHBeAg reduction between the VR(+) and VR(−) groups (P < 0.001). When log qHBeAg was evaluated according to the SR status, a steeper decrease was noted in the SR(+) group (from 1.44 ± 1.10 to −0.72 ± 0.46 PE IU/mL, P = 0.003) versus the SR(−) group (from 1.45 ± 1.04 to 0.60 ± 0.94 PE IU/mL, P < 0.001; Fig. 2B). Statistical differences were noted from month 6 between the SR(+) and SR(−) groups (P < 0.05).
Predictors for VR and SR.
Predictors for VR were investigated in HBeAg(+) patients. Among the baseline characteristics, multivariate analysis showed that higher ALT levels (P = 0.013), lower HBV DNA levels (P = 0.040), and lower qHBsAg levels (P = 0.033) were significantly associated with VR (Table 2). The predictive value was compared with the area under the receiver operating characteristic curve (AUROC), in which qHBsAg yielded the highest value of 0.823 (Fig. 3A). According to the ROC curve, the accuracy of predicting VR was highest with a sensitivity of 86.8% and a specificity of 78.9% at log qHBsAg = 3.98 IU/mL, which is equivalent to approximately 9550 IU/mL (on a nonlogarithmic scale). The corresponding positive predictive value (PPV) and negative predictive value (NPV) were 89.2% and 75.0%, respectively. Among the on-treatment factors, declines of HBV DNA, qHBsAg, and qHBeAg between the baseline and 6 months were investigated. There was a tendency toward differences in the decline in log qHBeAg with values of 0.72 ± 1.01 and 0.39 ± 0.34 PE IU/mL (P = 0.071) for the VR(+) and VR(−) groups, respectively. Meanwhile, the reductions of log HBV DNA were 4.13 ± 1.27 and 3.98 ± 1.84 copies/mL (P = 0.722) in the VR(+) and VR(−) groups, respectively, and the reductions of log qHBsAg were 0.07 ± 0.53 and 0.21 ± 0.42 IU/mL (P = 0.322), respectively.
|Characteristic||VR(+) (n = 38)||VR(−) (n = 19)||Univariate P Value||Multivariate P Value||AUROC for VR|
|Age, years (mean ± SD)||46.3 ± 9.1||44.7 ± 8.5||0.531||—||—|
|Male sex [n (%)]||25 (65.8)||14 (73.7)||0.572||—||—|
|ALT, IU/L (mean ± SD)||91.5 ± 72.2||61.9 ± 36.0||0.099||0.013||0.619|
|HBV DNA, log copies/mL (mean ± SD)||6.68 ± 1.10||7.92 ± 1.14||<0.001||0.040||0.812|
|qHBsAg, log IU/mL (mean ± SD)||3.48 ± 0.65||4.22 ± 0.68||<0.001||0.033||0.823|
|qHBeAg, log PE IU/mL (mean ± SD)||1.11 ± 1.04||2.11 ± 0.65||<0.001||0.130||—|
In the analysis of SR predictors, no baseline characteristics were significant. As for on-treatment factors, only a decline of log qHBeAg through month 6 was significant, with a reduction of 1.71 ± 0.27 PE IU/mL in the SR(+) group versus 0.43 ± 0.63 PE IU/mL in the SR(−) group (P = 0.001). In the ROC curve, the accuracy of predicting SR was highest with a sensitivity of 75.0% and a specificity of 89.8% with a reduction of log qHBeAg to 1.00 PE IU/mL, which is equivalent to a 10-fold decrease on a nonlogarithmic scale (Fig. 3B). The corresponding PPV and NPV were 54.5% and 95.7%, respectively.
Correlations Among HBV DNA, qHBsAg, and qHBeAg.
Overall, a modest correlation was detected between HBV DNA and qHBsAg in HBeAg(+) patients (n = 285, r = 0.328, P < 0.001), and a very weak correlation was found in HBeAg(−) patients (n = 190, r = 0.175, P = 0.016). A stronger correlation was detected between qHBsAg and qHBeAg (n = 285, r = 0.416, P < 0.001) and between HBV DNA and qHBeAg (n = 285, r = 0.570, P < 0.001). Analyses were further conducted with temporal ETV therapy. A significant correlation between HBV DNA and qHBsAg was observed only in HBeAg(+) patients, with none evident in those with HBeAg(−) disease (Table 3). Although a small increase was observed in the early period, a decreasing tendency was seen for the correlation coefficient in HBeAg(+) patients with maintenance of ETV therapy (Fig. 4).
|0 Months||6 Months||12 Months||18 Months||24 Months|
|r Value||P Value||r Value||P Value||r Value||P Value||r Value||P Value||r Value||P Value|
|HBV DNA versus qHBsAg|
|HBV DNA versus qHBeAg||0.554||<0.001||0.614||<0.001||0.641||<0.001||0.607||<0.001||0.625||<0.001|
|qHBsAg versus qHBeAg||0.407||0.002||0.297||0.025||0.456||<0.001||0.418||0.001||0.438||0.001|
Advances in the quantification of serum qHBsAg have opened a new path for furthering our understanding of HBV.27 qHBsAg is known to reflect cccDNA, which is the viral template for HBV replication in the maintenance of chronic infection, and the correlation between these two factors has been previously addressed.6, 7, 28 In addition, qHBsAg has a clinical role in predicting the response to antiviral therapy in patients undergoing PEG-IFN treatment. A 1 log IU/mL drop in qHBsAg at week 24 of therapy was shown to predict SVR (NPV = 97%, PPV = 92%), and a low qHBsAg level at week 48 with an on-treatment decline > 1 log IU/mL was shown to be associated with sustained HBsAg clearance.13, 14 In contrast, the clinical usefulness of qHBsAg in patients receiving oral nucleos(t)ide analogues remains largely unknown; previous studies have investigated the relevance of qHBsAg in patients treated with LAM or adefovir, which are known to be less potent agents.4, 6, 9 Furthermore, for the most part, the available data were not derived from independent studies but were incorporated into studies in which either a combination was used or a comparison with PEG-IFN was made.7, 10-12, 14, 29 Therefore, the data in this study are valuable because the clinical significance of serial qHBsAg was systematically analyzed in patients treated with ETV as a first-line therapy for CHB.
We report a significant decrease in qHBsAg with ETV therapy. However, the overall decline was modest, with a mean drop of −0.24 log IU/mL in HBeAg(+) patients and a mean drop of −0.21 log IU/mL in HBeAg(−) patients after 2 years of therapy. Although this was greater than the drop achieved with 1 year of LAM (−0.02 log IU/mL), it was less than that reported with PEG-IFN (−0.71 log IU/mL).14 There are several potential explanations for this modest decline of qHBsAg. First, the mechanism of action of oral nucleos(t)ide analogues is the suppression of viral replication through inhibition of HBV polymerase; because HBsAg production proceeds by a pathway distinct from that of HBV DNA, the effect of ETV on qHBsAg is possibly less prominent.24 Second, the HBV genotype seems to play a major role in qHBsAg. In a large series of retrospective data by Gish et al.,16 less HBsAg loss was seen in patients with genotype C (0.5%, 1/201) versus patients with genotype A (7.7%, 15/194) or D (8.1%, 7/79). Our entire cohort was infected with genotype C HBV, and this may also explain the modest decline in qHBsAg.
We have shown that the baseline qHBsAg level has a high predictive value for VR in HBeAg(+) patients (AUC = 0.823, P < 0.001) with a sensitivity of 86.8%, a specificity of 78.9%, a PPV of 89.2%, and an NPV of 75.0%. These values compare favorably to those reported for the prediction of SVR in patients treated with PEG-IFN (86%, 56%, 43%, and 92%, respectively).7 We were unable to further enhance the on-treatment predictive value of changes in qHBsAg; this might be due to the modest decline in the titers. Taken together, these results demonstrate that qHBsAg has clinical utility in the prediction of VR in HBeAg(+) patients and that a single titer at the baseline provides the best predictive value. Meanwhile, because almost all HBeAg(−) patients achieved VR (36/38, 94.7%), VR prediction in this group was neither statistically appropriate nor clinically valuable.
Even though there is less activity in comparison with qHBsAg, studies on qHBeAg have continued to be reported since Perrillo et al.18 suggested its clinical role in patients receiving conventional IFN therapy. Others have also reported associations with qHBeAg and clinical responses or virological breakthrough in patients treated with LAM and PEG-IFN.17, 19-21 Most recently, a thorough investigation that included both qHBsAg and qHBeAg was conducted to identify their relationship with intrahepatic markers of HBV replication, and it suggested potential practical implications for these quantitative serological markers.24 Our study is the first to report serial qHBeAg values in patients on ETV therapy. We have shown that a decline in qHBeAg is highly predictive for SR with sensitivity and specificity values as high as 75.0% and 89.8%, respectively. In other words, if a 10-fold drop in qHBeAg is encountered with 6 months of ETV therapy, there is a good chance of SR in such patients.
Recent investigations have alluded to a potentially interesting aspect of qHBsAg as antigen expression in the natural course of HBV infection. Two independent groups found that the level of qHBsAg was higher in the immune-tolerant and immune-clearance phases than in the low-replicative phase and in patients with HBeAg(−) disease.22, 23 These discrepancies in qHBsAg across different phases of CHB infection and in correlation between qHBsAg and HBV DNA provide evidence that different pathways exist for HBsAg and HBV DNA production as well as that HBV may integrate into the host genome. In addition, similar published results have demonstrated a good correlation in HBeAg(+) patients (r = 0.69, P < 0.001), whereas the association between HBsAg production and HBV replication broke down in HBeAg(−) patients (r = 0.28, P = 0.012); this was assumed to occur when HBsAg was produced from a source other than cccDNA.24 These reports suggest that the correlation between qHBsAg and HBV DNA without antiviral treatment is more significant in the higher HBV replicative phase than in the low-replicative phase. As expected, our study on patients receiving ETV demonstrated a significant correlation between HBV DNA and qHBsAg only in HBeAg(+) patients. This correlation coefficient peaked at 6 months and gradually decreased over time. A possible explanation for this is that the proportion of patients with undetectable or lower HBV DNA levels increased with ETV therapy, and this led to a similar status for the low-replicative phase. Moreover, a modest decline of qHBsAg during ETV therapy could not catch up with the rapid reduction of HBV DNA, and the result was the disproportional status of these two parameters. This explanation, however, warrants further validation because the dynamic relation between qHBsAg and HBV DNA should be understood in the context of overproduction of defective HBsAg particles and the role of integrated HBV DNA.30
Some limitations of this study need consideration. First, only Korean patients with genotype C HBV were included in this study. Although homogeneity in a study population is in some ways favorable, it limits generalization. Second, no cellular experiments were performed in this study; an investigation into intracellular markers and a correlation with them would have been very useful in validating the present data,24 and an analysis of integrated HBV DNA is needed to detect its potential relationship with serum qHBsAg. Finally, qHBsAg and qHBeAg were measured in stored samples, so a falsely low titer might have been seen because the natural decay of viral proteins led to error in the titers.
In conclusion, we report a systematic analysis of 2 years of serial qHBsAg and qHBeAg data for patients treated with ETV. The baseline level of qHBsAg and the on-treatment decline of qHBeAg in HBeAg(+) patients were proved to be highly useful in predicting VR and SR, respectively, and this lends support to the clinical utility of quantitative serological markers. In addition, these inexpensive and simple assays provide insight into the dynamic nature of the association between qHBsAg, qHBeAg, and HBV DNA in patients receiving antiviral therapy; further studies are warranted to validate and explore their potential role.
- 11On-treatment HBsAg decline during peginterferon alfa-2a (40KD) ± lamivudine in patients with HBeAg-positive CHB as a potential predictor of durable off-treatment response [Abstract]. Hepatology 2008; 48: 714A., , , , , , et al.
- 12Correlation between HBV cccDNA and HBsAg levels and their reduction by peginterferon alfa-2a based therapy in patients with chronic hepatitis B [Abstract]. Hepatology 2008; 48: 746A., , , , , , et al.
- 29Efficacy and safety of peginterferon alfa-2a versus adefovir dipivoxil (ADV) in treating lamivudine resistant HBeAg positive CHB: an interim analysis of a prospective randomised study [Abstract]. Hepatology 2008; 43: 745A., , , , , , et al.