CDC HBV recommendations updated.

Discovery of the hepatitis B virus (HBV) earned Baruch Blumberg, MD, PhD, the Nobel Prize in 1976 and opened an exciting era of research that yielded breakthrough tests for HBV that are widely used today in blood-donor screening and patient diagnosis and management. Through the years, as knowledge about the virus increased, scientists identified several distinct diagnostic markers for HBV that allow clinicians to diagnose and stage the infection and assess immunity.

Although immunization programs have significantly reduced the incidence of HBV in the United States, the prevalence of chronic HBV infection remains high. Estimates for the number of chronically infected individuals in the United States are as high as 1.4 million to 2 million. (1), (2) Worldwide, 350 million people are chronically infected with HBV, and about a third of the world's population has a current or past infection. (3)

Recently, the U.S. Centers for Disease Control and Prevention (CDC) and the European Association for the Study of the Liver (EASL) convened expert panels to update and expand their respective previous recommendations for identification and public-health management of persons with chronic hepatitis B infection. (1) (3) The factors prompting these revisions included the changing epidemiology of chronic HBV; the potential for serious liver disease among chronically infected persons from endemic areas who were infected as infants or children; and the availability of improved antiviral therapies. Coinciding with World Hepatitis Day earlier this year, the new CDC recommendations were discussed by Dr. John Ward, director of the Division of Viral Hepatitis at the CDC, and co-author of the CDC recommendations published in MMWR. (4)

In his remarks. Dr. Ward explained that a significant epidemiological influence in the United States has been increasing immigration of individuals from areas of the world with intermediate-to-high prevalence of HBV infection. In a high-prevalence area, 8% or more of the population is positive for HBV and intermediate prevalence is defined as 2% to 7% positivity. (1) Between one-third and two-thirds of chronically infected people are unaware of their infection. (4)

Testing these individuals and other risk groups identified by the CDC is critical to diagnose active disease, prevent ongoing transmission of HBV, offer vaccination to close contacts, provide antiviral therapy, and prevent later onset of cirrhosis or liver cancer. Some 15% to 25% of persons with chronic HBV die from HBV-related cirrhosis and liver cancer. (1)

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In addition to individuals from regions of high-and-intermediate endemicity, the CDC also added new recommendations for HBV testing in unvaccinated persons born in the United States whose parents are from areas of high HBV endemicity, injection-drug users, men who have sex with men (MSM), and persons taking immunosuppressive drugs for treatment of cancer and other diseases or to prevent rejection of transplanted organs. (1)

As in previous recommendations, the CDC advises using tests for hepatitis B surface antigen (HBsAg), antibody to HBsAg (anti-HBs), and antibody to hepatitis B core antigen (anti-HBc) to evaluate persons for current or past HBV infection. Combinations of these tests are recommended for use in various at-risk populations. These assays are widely available in laboratories nationwide on automated immunoassay systems.

HBsAg is the outer envelope protein of the virus and is a marker of acute or chronic infection. Anti-HBs indicates recovery and immunity from a resolved infection or immunity through vaccination, and anti-HBc is a marker of current or past infection. In persons with resolved infection, HBsAg becomes undetectable while anti-HBs and anti-HBc remain for life. In some resolved infections, however, anti-HBs levels may wane over time, leaving anti-HBc as the only indicator of past infection. Anti-HBc may also be the only detectable serologic marker in some chronic infections in which the level of HBsAg is too low to be detected by current commercially available assays.

An intriguing facet of HBV is its potential to persist in the liver for many years after apparent recovery from infection. (5) Anti-HBc is an important marker in these cases and might be the only detectable serologic indicator of past infection. The expanded CDC recommendations note there is a risk of reactivation in persons with resolved HBV infection who receive immunosuppressive therapy for other medical conditions. They also recommend that persons who are anti-HBc positive should be monitored closely for signs of liver disease. This patient group includes persons receiving chemotherapy, immunosuppression related to organ transplantation, and immunosuppression for rheumatologic or gastroenterologic disorders.

Armed with these recommendations, public-health organizations and healthcare professionals can direct their outreach efforts to educate and motivate the expanded at-risk populations to get tested for HBV and help reduce the consequences of this serious disease.

References

(1.) Weinbaum CM, Williams I, Mast EE, et al. Recommendations for identification and public health management of persons with chronic hepatitis B virus infection. MMWR. 2008;57(RR08):1-20.

(2.) Gish RG, Gadano AC. Chronic hepatitis B: current epidemiology in the Americas and implications for management. JViral Hepatitis. 2006;13:787-798.

(3.) European Association for the Study of the Liver. EASL clinical practice guidelines: management of chronic hepatitis B. JHepato. 2009;50:227-242.

(4.) Ward J. "Improving Diagnosis of Chronic Hepatitis B: Updated CDC Guidelines on Populations Recommended for Testing and Specific Testing Considerations," educational webcast sponsored by Abbott Diagnostics. May 19, 2009.

(5.) Marusawa H, Uemoto S, Hijikata M, et al. Latent hepatitis B virus infection in healthy individuals with antibodies to hepatitis B core antigen. Hepatology. 2000;31 (2):488-495.

Mary C. Kuhns, PhD, RM(NRCM), M(ASCP) (CM), is a Volwiler Research Fellow and manager of infectious diseases in the global scientific affairs group at Abbott Diagnostics in Abbott Park, IL Dr. Kuhns received her doctorate in microbiology and developmental biology from Ohio State University and completed her postdoctoral training in genetics at Yale University School of Medicine. She has published extensively on immunoassays and nucleic-acid testing in hepatitis diagnostics.