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Determinants for Spontaneous HBsAg Seroclearance in Persons with Chronic Hepatitis B Virus Infection By Bianca Malcolm Candidate for the Master of Public Health Degree Community-Based Master’s Project Oral Defense May 8, 2006 Faculty Chair: Longjian Liu, M.D., Ph.D., MSc Community Preceptor: Alison Evans, Sc.D.
I would like to take this opportunity to thank Alison Evans, my community preceptor, and Gang Chen of Fox Chase Cancer Center for providing me with the data for my analysis and assisting me with my analysis. I also thank Dr. Longjian Liu, my faculty advisor, of the Department of Epidemiology and Biostatistics at Drexel University School of Public Health who provided me innumerable support and guidance during my Community Based Master’s Project. Finally, I would like to thank all participants in the original study for making this secondary data analyses possible.
Statement of the Problem
Background and Significance
Research Design and Methods
Value to the Community
Background: Spontaneous hepatitis B surface antigen (HBsAg) seroclearance is a rare event in patients with chronic hepatitis B virus (HBV) infections and there is little available literature on it.
Objective: This study intended to identify determinants for HBsAg seroclearance in persons with chronic HBV using a large cohort of Chinese patients with 11 years of follow-up.
Design/Methods: This secondary data analysis used the database of a prospective cohort study of 1863 subjects who had returned 11 years after initial cohort entry (1992-93) to undergo further testing of viral markers and HBsAg-status. Of those 1863 subjects, 341 (18.30%) had apparently cleared HBsAg by 2003. Spontaneous HBsAg seroclearance was investigated in terms of its relationship to age, HBeAg-status, gender, HBV-DNA viral load, and history of clinical hepatitis.
Results: Of the 365 persons who were 50 years and older, 93 (25.47%) spontaneously cleared HBsAg. In contrast, only 248 (16.56%) of the 1498 subjects younger than 50 years of age cleared HBsAg (p<.0001). The incidence of HBsAg seroclearance was also significantly higher in persons who were HBeAg-negative compared to persons who were HBeAg-positive (21.52% vs. 13.17%; p <.0001). And HBsAg seroclearance incidence was higher in persons with a low-positive (21.37%) HBV-DNA viral load than in persons with either a negative (16.77%) or a high-positive (14.13%) viral load (p=.0009).
Conclusions: Results suggest that the age of patients, HBeAg-status, and HBV-DNA viral load are determinants for spontaneous HBsAg seroclearance. However, gender and history of clinical hepatitis did not significantly influence the occurrence of HBsAg seroclearance.
Statement of the Problem
Hepatitis B virus (HBV) infection is a major global public health concern because it is closely associated with serious sequelae, most notably liver cancer and cirrhosis.
Universal childhood hepatitis B vaccination programs have dramatically reduced the incidence, mortality, and morbidity of HBV in the U.S. and Western Europe.
However, HBV is increasingly prevalent worldwide, especially in Asian countries where the disease is endemic.
Chronic HBV infection is when a person remains positive for HBsAg for more than six months. These persons usually remain HBsAg positive indefinitely.
However, a significant portion of chronic carriers (0.1-2%) spontaneously clears serum HBsAg per year.
Previous studies have shown that certain factors (e.g. age, gender, HBeAg-status, HBV-DNA viral load) may influence the incidence of spontaneous clearance of HBsAg in the blood.
This analysis used a large series of Chinese persons to investigate the relationship of baseline factors to the occurrence of spontaneous HBsAg seroclearance.
Background and Significance
Worldwide Hepatitis B statistics:
> 2 billion people (1/3 of the world’s population) have been infected
800 million infected persons
350 million chronic carriers
50 million new cases/year
Accounts for 60-80 percent of liver cancer cases (the leading cause of liver cancer)
Accounts for 500,000 to 1.2 million deaths per year (10th leading cause of death worldwide)
How Hepatitis B Progresses
Previous Studies’ Findings
Liaw, et al. (1991) found that subjects who were HBeAg negative or older than 40 years of age at entry had higher incidences of delayed HBsAg clearance.
Kato, et al. (2000) also found that spontaneous HBsAg seroclearance was dependent on age.
Furusyo, et al. (1999) found that persons older than 50 years of age and/or HBeAg-negative were more likely to clear HBsAg than other subjects.
This study seeks to identify determinants that will increase the incidence of spontaneous HBsAg seroclearance and, subsequently, decrease the occurrence of poor outcomes.
Contribute to current scarce literature on HBsAg seroclearance.
Two main hypotheses are:
Persons infected with chronic HBV who are ≥ 50 years of age at cohort entry are more likely to undergo HBsAg seroclearance than their counterparts who are < 50 years of age at entry.
Persons infected with chronic HBV who are negative for hepatitis B e antigen (HBeAg) at cohort entry are more likely to achieve spontaneous HBsAg seroclearance than those who are HBeAg-positive at cohort entry.
Research Design and Methods
This is a secondary data analysis performed on the database of a prospective cohort study.
In 2003, 1863 randomly selected Chinese chronic HBV carriers (out of an initial 18,000) returned, 11 years after initial entry into the study (1992-93), for further serum testing of viral markers and HBsAg-status.
Of those 1863 patients, 341 (18.3%) had apparently cleared HBsAg by 2003.
Statistical analysis was conducted by the x 2 test, Student’s t test, and logistic regression by SAS v.8 statistical analysis software.
Demographics of the Study Population
Univariate Analysis for Clearance of HBsAg
Significant Factors for Clearance of HBsAg
Non-Significant Factors for Clearance of HBsAg
Multivariate Analysis for Clearance of HBsAg
Odds Ratios of Significant Factors for Clearance of HBsAg
Odds Ratios of Non-Significant Factors for Clearance of HBsAg
Age and HBeAg-status significantly influenced the incidence of spontaneous HBsAg clearance, which is consistent with previous evidence on HBsAg clearance.
Older persons may be more likely to clear HBsAg because they have had the virus longer in their systems.
Clearance of HBeAg means that virus replication has stopped, therefore, HBeAg-negative persons are in a better position to clear HBsAg than HBeAg-positive persons.
Although males have higher incidences of chronic HBV infection and females are more likely to clear HBeAg, sex did not significantly influence HBsAg clearance.
Strengths of the study:
Large series of patients provides lots of power for study results.
11 years of follow-up is a long enough period to sufficiently observe HBsAg clearance in population.
Limitations of the study:
Initial chronic HBV infection is unknown.
Exact time of HBsAg clearance, if applicable, is unknown.
Unable to compare baseline factors of original cohort of chronically infected persons with this sample => decreased validity.
Results suggest that the age of patients and HBeAg-status are determinants for clearance of HBsAg.
Persons older than or 50 years of age and/or HBeAg-negative were more likely to spontaneously clear HBsAg than any other group.
Although the % differences for clearance of HBsAg were significant for HBV-DNA viral load, this variable was found to be not independent of other study variables.
Gender and history of clinical hepatitis did not significantly influence the occurrence of spontaneous HBsAg seroclearance.
Future studies should concentrate on determining the exact time infected persons contract chronic hepatitis B and the exact time they clear the virus, if applicable.
Hepatitis B vaccination is the most efficient method of preventing HBV and HBV-related illnesses (1st anti-cancer vaccine), therefore, future policy should focus on:
Preventing mother-to-infant transmission through the administration of HBV vaccines at birth
Increasing child vaccination coverage; and
Increasing adult vaccination coverage, especially in Asian populations.
Future policy should also focus on improving medical services, detection, and treatment for chronic HBV carriers, especially in Asian populations.
Value to the Community
The Asian and Pacific Islander community (domestic and abroad) have notoriously low rates for HBV vaccination and series completion.
The results from this study can be used by researchers, public health officials, and clinicians to inform future research and interventions for hepatitis B, especially future efforts to vaccinate API children.
Fox Chase Cancer Center can also use this study to further investigate the benefits of HBsAg clearance in persons with chronic hepatitis B infection.
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