The Natural History of Chronic Hepatitis B
Virus Infection
Brian J. McMahon
Chronic hepatitis B virus (HBV) infection has a complicated course. Three phases are
identiﬁed: an immune tolerant phase with high HBV DNA and normal alanine aminotransferase (ALT) levels associated with minimal liver disease; an immune active phase with high
HBV DNA and elevated ALT levels with active liver inﬂammation; and an inactive phase
with HBV DNA levels < 2000 IU/mL and normal ALT levels with minimal inﬂammation
and ﬁbrosis on liver biopsy. Affected persons can move progressively from one phase to the
next and may revert backward. The primary adverse outcomes of chronic HBV infection are
hepatocellular carcinoma (HCC) and cirrhosis. Published natural history studies were reviewed and ranked by the strength of evidence regarding the study design. Factors with the
highest evidence of risk for development of HCC or cirrhosis from population-based prospective cohort studies include male sex, family history of HCC, HBV DNA level above 2000
IU/mL in persons above age 40, HBV genotypes C and F, and basal core promoter mutation.
Those with the next highest level of evidence include aﬂatoxin exposure, and heavy alcohol
and tobacco use. Improved methods to identify persons at highest risk of developing HCC or
cirrhosis are needed to allow intervention earlier with antiviral therapy in appropriate
patients. Future studies should include prospective follow-up of established populationbased cohorts as well as new cohorts recruited from multiple centers stratiﬁed by HBV
genotypes/subgenotypes and clinical phase to determine the incidence of the various HBV
phases, HCC, and cirrhosis. Also, nested case-control studies assessing immunological and
host genetic factors among persons with active and inactive disease phases, HCC, and
cirrhosis could be conducted using these types of cohorts. (HEPATOLOGY 2009;49:S45-S55.)
Introduction
Between 350 million and 400 million persons worldwide are chronically infected with hepatitis B virus
(HBV).1 The two primary adverse outcomes of chronic
Abbreviations: ALT, alanine aminotransferase; anti-HBe, antibody to hepatitis
B e antigen; BCP, basal core promoter; HBeAg, hepatitis B e antigen; HBV,
hepatitis B virus; HCC, hepatocellular carcinoma; HCV, hepatitis C virus; HDV,
hepatitis D virus; HIV, human immunodeﬁciency virus; PC, precore; REVEALHBV, Risk Evaluation of Viral Load Elevation and Associated Liver Disease/
Cancer-Hepatitis B Virus study.
From the Liver Disease and Hepatitis Program, Alaska Native Tribal Health
Consortium, Anchorage, AK, and Arctic Investigations Program, Division of
Emerging Infections and Surveillance Services, National Center for Preparedness,
Detection, and Control of Infectious Diseases, Centers for Disease Control and
Prevention (CDC), Anchorage, AK.
Received October 23, 2008; accepted February 3, 2009.
Supported by the Alaska Native Tribal Health Consortium and the Arctic Investigations Program, Centers for Disease Control and Prevention.
Address reprint requests to: Brian J. McMahon, M.D., Alaska Native Medical
Center, 4315 Diplomacy Drive, Anchorage, AK 99508. E-mail: [email protected];
telephone: 907-729-3419.
Copyright © 2009 by the American Association for the Study of Liver Diseases.
Published online in Wiley InterScience (www.interscience.wiley.com).
DOI 10.1002/hep.22898
Potential conﬂict of interest: Nothing to report.
infection are hepatocellular carcinoma (HCC) and cirrhosis, either of which can lead to a liver-related death.
The natural history of chronic HBV infection in individuals is complex, and infected persons can pass through
several phases. Patients can move from a state of high viral
load and no liver disease to one of active liver disease,
followed by inactive disease, and then revert back to active
liver disease years later. Progression to advanced ﬁbrosis
can be rapid, slow, or sporadic. During the inactive periods, hepatic inﬂammation, ﬁbrosis, and even early cirrhosis can be reversed over time only to reappear again if the
disease reactivates. Thus, chronic hepatitis B is a dynamic
condition and it is difﬁcult to predict what will happen
over time to an individual with this chronic infection.
Understanding the natural history of chronic hepatitis
B is important because it can guide the clinician in deciding on the need and optimal timing for initiating antiviral
therapy. The purpose of this article is to review the published literature on the natural history of chronic HBV
infection to extract the best available evidence in regard to
conclusions on management. In addition, because there
are many gaps in the understanding of the natural history
S45
S46
MCMAHON
Table 1. Proposed Scoring System for Evidenced-Based
Studies on the Natural History of Chronic HBV Infection
Level 1: Strongest evidence
• 1a: Population-based longitudinal cohort study with HBsAg-negative
comparison group
• 1b: Population-based longitudinal cohort study with no comparison group
Level 2: Intermediate evidence
• 2a: Clinic-based longitudinal cohort study
• 2b: Population-based or clinic-based cohort nested case-control study
• 2c: Cross-sectional clinic-based case-control study
Level 3: Weakest evidence
• Case series or observational study
of chronic HBV infection, this article will conclude with
suggestions for future studies that could help resolve some
of these questions.
Evaluating Studies on the Natural History
of Chronic HBV Infection
Many studies pertaining to the natural history of HBV
have been published in the past three decades. However,
these studies vary in quality of design and conduct. Few
are prospective and fewer of those are population-based.
Many are clinic-based case-control studies or case series.
For these reasons, in reviewing the literature on this topic,
a score was assigned to each study ranking the strength of
the evidence that led to the conclusions (Table 1). Because natural history studies involve observation and not
intervention, they are not “randomized” in the same way
as prospective clinical trials which are typically assigned
the highest scores for strength of medical evidence. Therefore, the strongest evidence-based rating score was assigned to longitudinal, prospective, population-based
studies that followed cohorts of both HBV-infected and
HBV-uninfected individuals to determine outcome over
time. Outcomes could include HCC, cirrhosis, liver inﬂammation and/or ﬁbrosis, or even resolution of liver
disease. The weakest evidence scores were attributed to
clinic-based studies involving infected patients evaluated
at one time point, comparing characteristics of those who
had developed an adverse outcome to those who had not.
The level of available evidence, based on the scoring system shown in Table 1, is listed in parentheses after the
association of interest.
Adverse Outcomes of HBV Infection: HCC
and Decompensated Cirrhosis
Longitudinal prospective outcome studies have clearly
shown that patients with chronic HBV infection have a
considerable risk of developing HCC during their lifetime
(1a, 1b). Most compelling was the classical study by Beasley and colleagues conducted in Taiwan in the early
HEPATOLOGY, May 2009
1970s.2 They screened 22,707 male railway workers for
HBV markers, identiﬁed 3454 hepatitis B surface antigen
(HBsAg)-positive carriers, and followed both carriers and
noncarriers for a total of 75,000 person-years. The relative
risk of developing HCC was 223 for carriers versus noncarriers, HCC accounting for 54% of the deaths among
carriers compared to 1.5% among noncarriers. Since
these ﬁndings were published, a high incidence of HCC
has been reported from every country with high rates of
HBsAg, including most recently Greenland. Although
HCC occurs more frequently in HBV-infected men than
HBV-infected women with a ratio of 3:1 to 4:1 (1b),
HBV-infected women have also been shown to have a
higher risk of HCC (1b).3 Other risk factors for HCC
include older age (1a), family history of HCC (2c), presence of cirrhosis (1a, 2a), and hepatitis C virus (HCV)
coinfection (2c).2,4-10
The ideal study to establish the risk of developing cirrhosis would be a longitudinal population-based study
where all participants have serial liver biopsies to determine whether they have cirrhosis as well as to identify the
factors predictive of its development. However, such a
study has not been done, largely because of the discomfort
and invasiveness of liver biopsy and the current lack of
dependable surrogate markers for detecting cirrhosis. Cirrhosis becomes clinically apparent once decompensation
occurs, so that a more clinically measurable outcome for
assessing the natural history of HBV is establishing the
incidence of decompensated cirrhosis. One populationbased study found the incidence of decompensation to be
0.5% per 1000 person-years (1b).4 In clinic-based longitudinal studies, the overall incidence of development of
cirrhosis is 2%-3% per year (2a).11,12 Risk factors for developing cirrhosis include older age, presence of hepatitis
B e antigen (HBeAg), and elevated alanine aminotransferase (ALT) levels (2a). The survival rate for untreated
persons with compensated cirrhosis is 84% and 68% at 5
and 10 years, respectively, but the survival rate is only 14% at
5 years in persons who present with decompensated cirrhosis
(2a). In persons with compensated cirrhosis, long-term survival is negatively associated with HBeAg positivity in that
clearance of HBeAg improves survival and decreases the risk
of liver decompensation (2a).7,12-17
The Phases of Chronic Hepatitis B
Infection
In 2000 and 2006, the National Institutes of Health
(NIH) sponsored two research workshops on the management of chronic hepatitis B. The conference participants
deﬁned three phases of chronic HBV infection that are
now widely accepted: the immune tolerant phase, the immune active phase, and the inactive hepatitis B phase.18,19
HEPATOLOGY, Vol. 49, No. 5, Suppl., 2009
Table 2. Phases of Chronic Hepatitis B Infection
Immune Tolerant Phase
• Occurs primarily after perinatal infection from HBsAg/HBeAg-positive mother
• ALT levels are normal
• HBV DNA ⬎ 200,000 IU/mL (⬎1 million copies), often above 107-8 IU/mL
• Liver biopsy is normal or shows only minimal inﬂammation with no or
minimal ﬁbrosis
• Occurs most frequently in HBV genotype C infection
Immune Active (Clearance) Phase
• HBeAg-positive chronic hepatitis B
E Elevated ALT levels
E HBV DNA ⬎ 20,000 IU/mL
• Anti-HBe–positive chronic hepatitis B
E Elevated ALT
E HBV DNA ⬎ 2000 IU/mL
• Hepatic inﬂammation with or without ﬁbrosis on biopsy often present in
both HBeAg-positive and HBeAg-negative immune active phase
Inactive Phase
• Anti-HBe
• ALT levels normal
• HBV DNA ⬍ 2000 IU/mL
• Hepatic inﬂammation minimal or absent
• Hepatic ﬁbrosis may improve over time
• HBsAg clearance may eventually occur
In addition, a fourth phase, the recovery phase, was proposed (Table 2, Fig. 1).
In persons who develop chronic hepatitis B infection,
HBeAg is initially positive, accompanied by high levels of
HBV DNA and may remain so for a few years to several
Fig. 1. Algorithm to display the
natural history of chronic hepatitis B
virus infection.
MCMAHON
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decades. Most patients eventually lose HBeAg and develop antibody to HBeAg (anti-HBe). The observed rate
of clearance of HBeAg in persons with or without elevated
ALT levels averages between 8% and 12% per year
(1b,2a),4,20,21 but this rate is much lower in persons who
are in the immune tolerant phase.22,23 The rate and average age of seroconversion from HBeAg to anti-HBe varies
by HBV genotype, because persons infected with genotype C remain HBeAg-positive for many years longer
than those infected with genotypes A, B, D, or F (1b).24
The Immune Tolerant Phase. HBV-infected persons in the immune tolerant phase are HBeAg-positive,
have normal ALT levels, and elevated levels of HBV DNA
that are ⬎20,000 IU/mL and commonly well above 1
million IU/mL. The immune tolerant phase is thought to
occur most frequently in persons who are infected via
perinatal transmission from HBeAg-positive mothers.24
HBeAg may act as an immune tolerant protein that aids
the virus in avoiding detection by the immune system. In
immune competent persons, HBV is not cytopathic and
hepatocellular damage is induced by the host immune
system’s efforts to eliminate HBV. The immune tolerant
phase can last for a few years to more than 30 years (2b).25
During this phase, there is either no or minimal liver
inﬂammation or ﬁbrosis. However, because the HBV
polymerase gene has reverse transcriptase properties,
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MCMAHON
HBV integrates randomly into the host’s hepatocyte
DNA and during the immune tolerant phase, persistently
high levels of HBV DNA over many years would likely
mean an accumulation of integration sites, increasing the
risk of HCC over time even in the absence of active liver
inﬂammation and ﬁbrosis.
The Immune Active Phase. The immune active
phase, also sometimes referred to as the “chronic hepatitis
B phase” or the “immune clearance phase”, is characterized by elevated ALT levels and an elevated HBV DNA
level above at least 2000 IU/mL. Active liver inﬂammation is usually present with or without liver ﬁbrosis. Patients may be either HBeAg-positive or HBeAg-negative/
anti-HBe–positive.26 Persons infected after birth who
develop chronic HBV infection may advance to the immune active phase shortly after the time of infection,
whereas those infected via the perinatal route may transition into this phase several years after experiencing the
immune tolerant phase of HBV. In this phase, the host’s
immune system recognizes HBV as being foreign and
initiates an immune response that results in hepatocyte
damage. In persons who are HBeAg-positive, HBV DNA
levels may progressively fall, eventually resulting in seroconversion from HBeAg to anti-HBe. Seroconversion to
anti-HBe can be preceded by a ﬂare of hepatitis.21,27
Clearance of HBeAg that occurs spontaneously or as a
result of antiviral therapy reduces the risk of hepatic decompensation and improves survival.7,12-17,28,29
Anti-HBe–Positive Chronic Hepatitis B. Persons
with anti-HBe–positive chronic hepatitis B can present in
one of two ways. A small proportion, 10%-20%, will
remain in the immune active phase after seroconverting
from HBeAg to anti-HBe.21,30 Others will transition into
the inactive hepatitis B phase only to experience one or
more episodes of reactivation to the immune active
phase.31-35 These patients usually have lower levels of HBV
DNA (2000 IU/mL to 2 million IU/mL) than persons in the
HBeAg-positive immune active phase. There are reports in
some studies that the precore (PC) mutation, a G3 A mutation at codon 1896 that results in the occurrence of a stop
codon that renders the virus unable to encode for HBeAg, is
associated with HBeAg-negative active hepatitis B; however,
because PC mutations are also found in persons in the antiHBe–inactive carrier phase, it is uncertain whether the occurrence of these mutations actually promote or are
surrogate markers for liver inﬂammation.35-40 In most studies, a higher proportion of a double mutation in the HBV
basal core promoter (BCP) are found in persons with antiHBe–positive hepatitis.39,41
Inactive Hepatitis B Phase. The inactive hepatitis B
phase is characterized by the absence of HBeAg and the
presence of anti-HBe, normal ALT levels, HBV DNA
HEPATOLOGY, May 2009
⬍2000 IU/mL, and improvement in liver ﬁbrosis and
inﬂammation over time. Prospective studies conducted
for up to 10 years of persons in the inactive hepatitis B
phase have shown that in most of them, HBeAg remains
negative, ALT levels remain normal, and HBV DNA levels remain ⬍2000 IU/mL or even negative (2a).42-44
Moreover, liver ﬁbrosis is either absent or minimal in
degree and shows no evidence of progression over time in
those who remain in the inactive hepatitis B phase.43,44
However, a few clinic-based cross-sectional studies
have demonstrated that a minority of persons in the inactive HBV phase have had moderate, or occasionally even
severe, ﬁbrosis present on liver biopsy (2c).45 In these
studies, the inactive HBV phase was deﬁned as normal
ALT levels and HBV DNA ⬍2000 IU/mL for 3-12
months only. There are two conceivable explanations for
the ﬁnding of more than mild ﬁbrosis in a proportion of
patients in these studies. First, some patients may have
entered the inactive phase with already moderate to severe
hepatic ﬁbrosis before the observation period began and
liver ﬁbrosis may be in the process of slow regression.
Second, some persons may be having recurrent ﬂares of
anti-HBe–positive hepatitis interspersed with prolonged
periods of having normal ALT levels and may have been
mislabeled as being in the inactive phase. Thus, these
persons must be followed indeﬁnitely to be sure that they
remain in this phase.
Possible Events After Seroconversion from
HBeAg to Anti-HBe
Four possible scenarios can develop in HBV-infected
patients after HBeAg seroconversion (Fig. 1). First, approximately 20% of patients will experience one or more
reversions back to HBeAg positivity.4 These reversion/
seroconversion events are usually associated with ﬂares of
hepatitis. Recently, it was found that the proportion of
patients experiencing HBeAg reversion differs by HBV
genotype, with the highest risk (⬃40%) occurring in persons infected with genotypes C and F (1b).24 Second,
most patients (70%-80%) will go into the inactive hepatitis B phase where most will remain for life (1b,
2a).4,20,21,30,33,46 Third, after HBeAg/anti-HBe seroconversion, 10%-30% of patients will remain in the immune
active phase manifested by the continued presence of elevated ALT values and HBV DNA levels above 2000
IU/mL (2a).21,33,34 Finally, 10%-30% of persons who initially go into the inactive phase will later experience one or
more reactivations of anti-HBe–positive hepatitis, characterized by a rise in HBV DNA to ⬎2000 IU/mL accompanied or followed by a rise in ALT levels.21,33,34,47
Persons in whom HBeAg reversions occur or who have
HEPATOLOGY, Vol. 49, No. 5, Suppl., 2009
reactivation of anti-HBe–positive chronic hepatitis appear to be at higher risk of developing HCC or cirrhosis.4
Spontaneous Clearance of HBsAg
Published studies have found that between 0.5% and
0.8% of chronically infected individuals will clear HBsAg
per year (2a).4,48,49 Predictors of HBsAg clearance are
older age and sustained presence of the inactive hepatitis
stage.4,48 The clinical outcome after clearance of HBsAg is
generally better than in persons who continue to be HBsAg-positive. Liver inﬂammation and ﬁbrosis improve
over time.50-52 In one study of 189 persons without cirrhosis at the time of HBsAg clearance, none developed
cirrhosis and all had normal ALT levels an average of 62
months after seroclearance.53 Persons who clear HBsAg
have been classiﬁed as being in the “recovery phase” of
hepatitis B.18 However, this term may be a misnomer
because several studies have clearly shown that HCC can
develop in some of these individuals years after HBsAg
clearance.4,50-53 In addition, HBV DNA can be found in
the serum of up to 21% of persons as long as 5 years after
HBsAg clearance. A higher proportion has detectable
HBV DNA in liver. Thus, although while the risk of
advancing liver disease and the development of cirrhosis
may have waned, the risk of HCC is still present, albeit
less likely. The ongoing risk of HCC may be due to two
factors. First, the presence of integrated HBV DNA in
hepatocytes that occurred over the years while HBV replication was high could conceivably trigger genomic mistakes during hepatocyte cell division that might result in
HCC. Second, HBV may well be still present in low levels
in chronically infected persons who cleared HBsAg. Thus,
persons who were previously chronically HBsAg-positive
and are later in the so-called “recovery phase” should still
be followed for the development of HCC, as recommended in the current practice guidelines.54
Risk Factors for the Development of HCC
and Liver Fibrosis
Risk factors identiﬁed to be associated with an increased risk of developing HCC, progressive liver disease
and cirrhosis are listed in Table 3. Demographic risk factors have been discussed above. Heavy alcohol use is a risk
factor for more severe liver disease, and aﬂatoxin exposure
has been shown to be a cofactor in increasing the risk of
HCC in HBV-infected persons.
Viral Risk Factors for HCC and Cirrhosis
HBV Genotype. Eight genotypes (A through H) of
HBV have been identiﬁed that differ from each other in
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Table 3. Factors Associated with the Increased Risk of
Progression of Liver Disease and Risk of HCC and Cirrhosis
in Persons with Chronic HBV Infection
Demographic
• Male Sex: Increased risk of HCC (1a)
• Age: Increase risk HCC with advancing age (1a,1b)
Social and Environmental
Alcohol: Increased risk for HCC and cirrhosis (2c)
• NAFLD: insufﬁcient data
• Aﬂatoxin exposure: increased risk of HCC (2c)
Viral
• HBV Genotype/sub-genotype risk for HCC and cirrhosis (1b, 2a, 2b)
• HBV DNA level over age 40 years for HCC and cirrhosis(1b)
• Viral coinfection
E HBV ⫹ HIV
—Increase HBV DNA levels (2c)
—Increased risk of cirrhosis/HCC (3)
E HBV ⫹ HCV: Increase risk of HCC (2a)
E HBV ⫹ HDV: Increase risk of cirrhosis (2c)
whole-genome sequencing by at least 8%.55 In addition,
multiple subgenotypes (1, 2, 3, etc.) have been identiﬁed
within the HBV genotypes, these differing by 4%-8%.56
Genotype A is found in Northern Europe and frequently
among Caucasians in the United States. Genotypes B and
C are common in Asian populations, including immigrants from Asia in the United States as well as ﬁrstgeneration and second-generation Asian Americans.
Genotype D is the most common genotype found in
Southern and Eastern Europe and is also common in the
Middle East. Genotype F is found in native populations
in North and South America. Genotype E, G, and H
infections are uncommon and their epidemiology is not
well characterized (Table 4).
A growing number of published studies have provided
evidence that the natural history of chronic HBV infection differs according to the speciﬁc infecting HBV genotype and subgenotype. Shown in Table 4 are the
geographic areas where speciﬁc HBV genotypes and subgenotypes have been found and includes clinical associations that have been made and the strength of evidence for
these associations. Genotype A1 is associated with HCC
in young men who are usually HBeAg-negative and antiHBe–positive, have low levels of HBV DNA, and rarely
have cirrhosis. Exposure to aﬂatoxin may be an important
cofactor for the occurrence of this outcome. Genotype A2
is associated with HCC in older persons. Compared to
HBV genotype D, genotype A2 is associated with a lower
risk of HCC and a greater likelihood of resolution of
active hepatitis, and clearance of HBV DNA and HBsAg.57
Genotype B is divided into two major groups: Bj found
in Japan and Ba found in the rest of Asia. Bj (B1 and B6)
is a “pure” strain of genotype B, while Ba (B2-5) contains
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MCMAHON
HEPATOLOGY, May 2009
Table 4. Geographic Distribution of Speciﬁc HBV Genotypes/Subgenotypes
Genotype
Geographic Region
A1
A2
A3
B1
B2-6
C1-4
Sub-Saharan Africa
Northern Europe
West Africa
Japan
East Asia
China, Korea, Southeast Asia, Japan,
South Paciﬁc Islands
D1-4
E
F1
F2
G
Russia, Middle East, Mediterranean,
North Africa, Eastern Europe, Indian
Subcontinent
West Africa
Alaska, Central America, South America
Central America, Amazon region
Europe, United States, Australia
H
Central America, Amazon region
Disease Association
HCC in young males often without cirrhosis
HCC and cirrhosis in older persons
Unknown
HCC and cirrhosis in older persons
HCC and cirrhosis occurs at younger age than B1
Higher risk of HCC and cirrhosis compared with genotypes B
HBeAg seroconversion occurs 1-3 decades later than in genotypes A, B,
D, and F1
Anti-HBe chronic hepatitis B, HCC, and cirrhosis in older individuals
Unknown
HCC in children and young adults in Alaska only
Unknown
Almost exclusively found in persons coinfected with other HBV genotypes,
mainly A1. Clinical signiﬁcance unknown.
Unknown
Strength of
Evidence
2c
2c
2c
2c
1b
1b,2a
2c
NA
2b
NA
NA
NA
NA, not available.
a portion of the genome of genotype C recombined into
the core region of genotype B. Ba is associated with older
age at the time of HBeAg seroconversion, a higher risk for
HCC, and a higher frequency of BCP mutations than
genotype Bj.58
Numerous studies have reported the clinical outcome
of chronic hepatitis in patients with HBV genotype C
infection compared to other HBV genotypes, especially
genotype B. There are compelling data (1b, 2a) from multiple population-based and clinic-based prospective trials
which show that HBV genotype C is independently associated with a higher risk of HCC than genotypes A2, Ba
and Bj, and D.59-62 Thus, HBV genotype C may be the
most treacherous of the HBV genotypes. A populationbased study from Alaska that included 1152 Alaska Natives with chronic HBV infection who were followed for
21 years found that 50% of those infected with HBV
genotypes A2, B6, D, and F1 cleared HBeAg before
reaching 20 years of age. In contrast, the average age of
HBeAg seroconversion in persons with genotype C was
47 years.24
HBV genotype D has been associated with HBeAgnegative chronic hepatitis and frequently harbors the PC
variant.40 However, persons infected with genotype D
and found to be in the inactive hepatitis B phase are likely
to remain in this phase without developing complications
of liver disease or HCC; in one study, 97% of those with
minimal or no ﬁbrosis or inﬂammation on liver biopsy
had no progression of histology on repeat liver biopsy
after 4 years of follow-up.44 A possible reason for these
conﬂicting ﬁndings could be that persons infected with
genotype D either go into the inactive hepatitis B phase
and stay there or develop chronic hepatitis (the immune
active phase of HBV) at the time of or shortly after HBV
seroconversion.
Studies are not available to assess the inﬂuence of HBV
genotypes E, G, and H on disease outcome. HBV genotype F1 has recently been shown to be associated with a
high risk of HCC in Alaska compared to HBV genotypes
A2, B1, and D, particularly in children and young adults
⬍30 years of age.62
Level of HBV DNA Associated with Active
Liver Disease
A few cross-section studies that examined the association of active liver inﬂammation and ﬁbrosis and HBV
DNA level found that approximately 90% of those with
active liver disease at the time of liver biopsy who are
HBeAg-negative/anti-HBe–positive and have an elevated
ALT level have an HBV DNA level of ⬎105 genomic
copies/mL (20,000 IU/mL), 10% have levels between 104
and 105 copies/mL (2000-20,000 IU/mL), and 1% have
⬍104 copies/mL.52,63 However, many persons in these
studies with HBV DNA levels above 104 or even 105
copies/mL have minimal or no ﬁbrosis or inﬂammation
on biopsy. Thus, while HBV DNA ⬎2000 IU/mL appears to be a reasonable level at which to evaluate persons
with chronic HBV infection for the extent of liver disease,
a liver biopsy may be necessary to identify those with the
signiﬁcant ﬁndings of moderate or severe inﬂammation
and ﬁbrosis. Thus, not all patients with HBV DNA levels
⬎2000 IU/mL have active liver disease or ﬁbrosis, but
most persons with levels ⬍2000 IU/mL have inactive
disease.
HEPATOLOGY, Vol. 49, No. 5, Suppl., 2009
HBV DNA Level and Risk of Subsequent
Development of HCC and Cirrhosis
In the past few years, several prospective populationbased studies have analyzed outcomes of HBV infection
in relation to the level of HBV DNA at the beginning of
the observation period. These studies have uniformly
shown that HBV DNA levels ⬎104 or 105 copies/mL
(⬃2000 or 20,000 IU/mL) are associated with an increased risk of HCC, and one study has shown that there
is an increased risk of developing cirrhosis.59,64-68 In all of
these studies, the mean age at enrollment was in the mid40s and follow-up was as long as 11 years. In the REVEAL-HBV (Risk Evaluation of Viral Load Elevation
and Associated Liver Disease/Cancer-Hepatitis B Virus)
study, 28,870 persons from 10 towns in Taiwan were
tested for HBV markers; 4155 were HBsAg-positive and
3653 had baseline HBV DNA levels tested. The median
age at enrollment was 46 years and the average age at a
median of 11.4 years follow-up was 57 years. Persons with
HBV DNA levels above 104 copies/mL were again tested
at end of follow-up and those whose levels remained
above 104 copies/mL were at increased risk of developing
HCC and cirrhosis.65,66 Other independent risk factors
identiﬁed besides HBV DNA levels were older age and the
presence of cirrhosis. This and the other prospective studies
provide strong evidence that for persons over age 40, HBV
DNA level above 2000 IU/mL is a risk factor for developing
HCC even in persons with ALT levels between 0.5 and 1.0
times the upper limit of the normal range.
However, there is at this time no evidence that persons
below the age of 40 years with HBV DNA levels above
2000 IU/mL are at increased risk of HCC until they reach
their 40s. One small prospective study of persons in the
immune tolerant phase whose mean age was 30 years
showed that those who remained in this stage (HBeAgpositive with normal ALT levels) had mild disease on
biopsy at entry, and on repeat biopsy 5 years later, had
minimal progression of ﬁbrosis. Those who developed
ALT elevations and remained HBeAg-positive had evidence of progressive ﬁbrosis and a marked increase in the
histologic activity index score.25 Additional prospective
studies of persons less than 40 years of age with elevated
HBV DNA levels are needed to clarify this issue.
Speciﬁc HBV Mutations and the Risk of
HCC and Cirrhosis
Speciﬁc mutations in the HBV genome, especially
those that result in amino acid changes in the viral peptides expressed by HBV, may affect the subsequent risk of
developing HCC or cirrhosis. Many studies have been
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reported on the consequences of a double substitution:
A1762T and G1764A in the (BCP) region of
HBV.39,41,62,69 The overwhelming evidence from both
cross-sectional and prospective studies is that BCP is an
independent risk factor for the development of active liver
disease and HCC. Even after adjusting for HBV genotype, BCP has been found to be an independent risk factor for HCC in persons infected with genotypes A2, B, C,
and D but not in genotype F1.62 Another mutation, the
precore mutant, has been associated with liver inﬂammation, especially anti-HBe–positive immune active HBV,
and the development of HCC in some but not all studies.39,40,62 Recently, the presence of the PC mutation was
associated with a lower risk of developing HCC independent of HBV genotype and BCP mutation.61 Other small
studies examining both the HBV core and the X regions,
and the pre-S region of the HBV envelope, have shown
that mutations in these areas might be important predictors of risk, but more deﬁnitive studies are needed before
any conclusions can be made.70,71
HBV Coinfections with HCV, Human
Immunodeﬁciency Virus or Hepatitis B
Delta Virus
Between 6% and 13% of persons infected with human
immunodeﬁciency virus (HIV) are also chronically infected with HBV, with the highest prevalence of coinfection found in sub-Saharan Africa.72 Coinfection with
HBV and HIV is associated with higher levels of HBV
DNA, lower rates of spontaneous HBeAg seroconversion,
and higher rates of liver-related mortality than monoinfection with HBV.73,74 Severe ﬂares of hepatitis have been
reported in patients coinfected with HBV/HIV with low
CD4⫹ T cell counts who experience immune reconstitution after initiation of highly active antiretroviral therapy.73 In addition, some coinfected patients with high
levels of HBV DNA and hepatic necroinﬂammation
may be HBsAg-negative but anti-HBc–positive (latent
HBV).73
In the United States and elsewhere, up to 15% of
HBV-infected persons are also infected with HCV, the
highest risk being found among injection drug users.75 In
developing countries, HCV coinfection is usually due to
use of poor sterile technique during vaccination and medical procedures.1 Acute HCV infection in persons with
chronic HBV infection can increase the risk of developing
severe, even fulminant, hepatitis.76 In HBV/HCV coinfected patients, HCV can become the dominant virus and
suppress HBV DNA levels.77 Patients with HBV/HCV
coinfection are at a much higher risk of developing
HCC.78,79
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MCMAHON
Hepatitis B delta virus (HDV) is a satellite virus dependent on HBV for production of its envelope protein.
Chronic HBV/HDV coinfection is primarily a result of
an HDV superinfection occurring in an individual chronically infected with HBV.80 Coinfection with both viruses
increases the risk of cirrhosis and hepatic decompensation.81
Combining Risk Factors to Better
Characterize Those at the Highest Risk of
Developing HCC and Decompensated
Cirrhosis
Recently, the authors of the REVEAL study used their
cohort to detect other viral-related risk factors for HCC
(Table 5). Independent risk factors identiﬁed in testing
the samples obtained at study entry included an HBV
DNA level of ⬎104 copies/mL (approximately 2000 IU/
mL), HBV genotype C (compared with genotype B), the
presence of BCP mutations, and surprisingly, the absence
of PC mutation. In those who had all three of these factors, the incidence of HCC was 2254 per 100,000 personyears of follow-up compared to those who were infected
with HBV genotype B, who did not have BCP but did
have PC mutation (174 per 100,000 person-years).61 To
put this into perspective, the risk of developing HCC over
the 11-year period of this study was almost 25% in those
who had all three independent risk factors, versus less than
2% in those who had none. This type of information
derived from well-designed natural history studies can be
of great help to clinicians in making decisions regarding
who should receive therapy for chronic HBV infection.
Conclusions
Natural history studies are crucial to understand not
only the outcome of chronic HBV infection, but also
what risk factors promote progression of disease and when
the best time is to intervene with antiviral therapy to
prevent the development of HCC and cirrhosis. To date,
the strongest risk factors for the development of HCC
and/or cirrhosis are male sex (1a), increasing age (1b),
HBV DNA ⬎2000 in persons over age 40, but not under
40 (1b), genotypes C and F1 (1b), family history of HCC
(1b), BCP mutation (1b), and presence of cirrhosis (1b).
Risk factors with lesser evidence include heavy alcohol or
tobacco use and aﬂatoxin exposure (2c). Factors for which
there is either insufﬁcient evidence to determine risk or
conﬂicting evidence include nonalcoholic fatty liver disease, HBV DNA ⬎ 2000 IU/mL in persons under 40
years, and the presence of PC mutation.
HEPATOLOGY, May 2009
Table 5. Stratifying Independent Risk Factors for
Development of Hepatocellular Carcinoma in a PopulationBased Prospective Cohort Study (REVEAL-HBV) in Persons
with HBV DNA > 104 copies/mL (2000 IU/mL)*
Risk Factor
Genotype
Genotype
BCP
No BCP
PC
No PC
Genotype
Genotype
C
B
C ⫹ BCP ⫹ No PC
B ⫹ PC ⫹ No BCP
Incidence of HCC per
100,000 Person
Years
% Who Would
Develop HCC Over
10 Years
786/100,000
237/100,000
1149/100,000
359/100,00
996/100,000
269/100,000
2254/100,000
174/100,000
8%
2%
11%
4%
10%
3%
23%
2%
*Modiﬁed from the REVEAL-HBV study.61
Needs for Future Research
At least 50%-60% of patients with chronic HBV infection will go through life without developing the lifethreatening complications of HCC or decompensated
cirrhosis. The goals of future natural history studies
should include the identiﬁcation of demographic, viral,
immunologic, host genetic, and social and environmental
factors that inﬂuence the outcome of HBV infection.
This information could then be used to develop monitoring strategies, including how often and what tests to use to
follow patients based on their risk proﬁle. For example,
from what is known from the REVEAL and other natural
history studies, persons over the age of 40, with HBV
DNA levels ⬎2000 IU/mL infected with HBV genotype
C, and who have BCP mutations, should undergo more
rigorous surveillance for HCC than those without such
risk factors. These patients might be recommended to
have serum markers and imaging tests performed every 3
rather than every 6 months and to start antiviral therapy
sooner. In contrast, persons over the age of 40 who are in
the inactive phase of hepatitis B might be advised to undergo surveillance less frequently, perhaps every 12
months, and they may not need antiviral therapy.
Two types of natural history studies would be useful.
First, established prospective population-based cohorts,
such as from the REVEAL or the Alaska cohort studies,
could be recruited to conduct nested case-control studies
examining viral, immunologic, and host genetic factors
associated with the three different phases of HBV infection, HCC, and cirrhosis. Secondly, additional prospective cohort studies could be established. These studies
would best be either multicentered national or international in scope. Because population-based studies are expensive, and because large numbers of persons need to be
screened to identify those who are infected with HBV,
future studies might have to be clinic-based. Medical cen-
HEPATOLOGY, Vol. 49, No. 5, Suppl., 2009
ters participating in these studies would be encouraged to
recruit patients in all three phases of HBV infection.
The ideal future prospective cohort natural history
study might include persons infected with each of the
major HBV genotypes/subgenotypes that occur most
commonly in the world. Those to date would include
genotypes A1, A2, A3, B1, B2-5, B6, C, D, F1, and possibly E and H. Genotype G appears to be uncommon.
Approximately 200-300 persons from each relevant genotype/subgenotype category could be recruited for a total
of between 2000 and 3000 participants, and then stratiﬁed by HBV phase of infection at enrollment. At enrollment, a history would be taken to include the use of
alcohol and tobacco, a physical examination would be
conducted, and laboratory tests would be performed that
include a complete liver panel; complete blood counts;
routine serum chemistries; lipid panel; fasting glucose and
insulin levels; HBV genotype; BCP and PC mutation
testing; HIV, HCV, and HDV antibodies; and HBV
DNA level. Sera would be stored and peripheral blood
mononuclear cells collected and stored for immunological studies. Participants would be evaluated and blood
drawn at least twice yearly for at least 5 years and liver
biopsies performed if HBV DNA levels were ⬎2000
IU/mL and ALT values were elevated, or regardless of the
ALT value, if HBV DNA levels were ⬎2000 IU/mL and
age ⬎40 years. The cohort would be observed for the
incidence of developing the immune active phase as well
as developing HCC and cirrhosis. It would be expected
that the incidence of subsequently developing HCC and
cirrhosis would be reduced, because patients in the study
would be offered antiviral therapy if indicated by existing
practice guidelines. The most important endpoint might
be the incidence of developing the immune active phase,
especially in those who have already undergone HBeAg
seroconversion, because this would be a potential time to
treat to prevent the risk of cirrhosis and HCC.
The questions asked of these prospective, as well as the
established cohort studies, would include the following:
(1) Are there any speciﬁc single or multiply occurring
mutations besides BCP that independently increase the
risk of developing the immune active phase, HCC, or
cirrhosis?
(2) What is the inﬂuence of alcohol, metabolic syndrome, and tobacco on progression of chronic hepatitis B
and the development of HCC and cirrhosis?
(3) What are the differences in the immunological response to HBV infection that underlie each of the three
phases?
(4) How might host genetics inﬂuence outcome?
Investigations using these cohorts might consist of a
nested case-control design comparing age-matched, sex-
MCMAHON
S53
matched, and HBV genotype–matched persons with an
adverse event (HCC, cirrhosis, or the immune active
phase) and persons in the immune tolerant and inactive
phases:
(1) Full-genome sequencing of HBV isolates to search
for signiﬁcant mutations or patterns of mutations that are
associated with each phase and outcome.
(2) Identiﬁcation by HBV genotype–speciﬁc peptides
that might elicit cytotoxic T cell responses to determine
which viral peptides and speciﬁc T cell epitopes are responsible for hepatocyte damage in chronic hepatitis B.
(3) Using gene chip analysis, identiﬁcation of genes
that are over-expressed and under-expressed in each phase
of HBV infection as well as in persons with HCC or
cirrhosis.
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