Viral hepatitis has a substantial global prevalence. Hepatitis B and C viruses (HBV and HCV) are one of the top global infections along with HIV, malaria and tuberculosis in terms of mortality. It is interesting to note that although the global mortality rates of HIV, malaria and tuberculosis have plummeted since 2008, the number of deaths owing to chronic HBV and HCV infections has persistently risen, with more than 1.4 million deaths occurring every year. Considering the increasing burden, elimination of viral hepatitis should be a global priority.
Some of the measures to decrease the burden of viral hepatitis include: the implementation of universal hepatitis B immunization and antiviral treatment of highly viremic mothers infected with HBV to prevent vertical transmission during the third trimester; screening blood donors for HBV and HCV; safe injection practices; stringent infection-control programmes; and antiviral treatments for patients with HBV and HCV infection.
Inspite of vaccines for viral hepatitis being available the global prevalence has not substantially declined mainly due to lack of screening. The global rates of diagnosis of hepatitis B and C are very low and averages to 8% and 18%, respectively. Also, in the case of HCV, where there is no vaccine, many studies have suggested that a test-and-screen strategy would be needed to eradicate those that are currently infected with HCV.
Screening for Hepatitis A
Screening for hepatitis A is done by testing for hepatitis A virus (HAV) antibodies. The result of the antibody test shows the current or past infectivity and vaccination status of an individual. Such an individual that tests positive for the HAV antibodies is immune to future HAV infection. A negative test result indicates that the individual has never been infected or vaccinated with HAV and is still susceptible to HAV infection.
Screening for Hepatitis B
HBV has three antigens (surface, core, and e) which are proteins that are found in different parts of the virus and can be detected in the blood. Whenever the HBV finds entry into the host body, the immune system produces antibodies corresponding to each type of these antigens (surface antibody, core antibody, and e antibody, respectively), which can also be detected in the blood. Thus, screening for hepatitis B includes testing for
- Hepatitis B surface antigen (HBsAg), which determines whether there is a current infection
- Hepatitis B core antibody (anti-HBc), which evaluates whether an individual has ever been infected in the past
- Hepatitis B surface antibody (anti-HBs), which finds out whether the virus has been cleared after infection, or if the individual has been vaccinated and is now immune to future infections
HBsAg is detectable in blood 4 to 10 weeks after exposure to hepatitis B virus. Most people will show a negative HBsAg test result within a few months once the blood is cleared of the virus while others continue to test positive and stay infected. If the HBsAg test continues to be positive even after 6 months, the HBV infection is then considered to be chronic in nature. Chronic hepatitis B diagnosis requires a further detailed evaluation.
The anti-HBc appears in the blood within a few weeks of HBV infection. A positive result, however, does not specify whether the virus is currently active, has been cleared, or has led to immunity towards future infections.
The anti-HBs are produced by the immune system to attack theinvading virus. These antibodies appear in individuals who have been either been vaccinated against HBV, or who had been infected in the past and cleared the virus from their bodies. A positive anti-HBs indicates lifetime immunity from hepatitis B. However, one can be safely vaccinated again even if they have been infected previously or have been vaccinated earlier.
Screening for Hepatitis C
HCV antibodies are the most common test for HCV. However, the results may be quite ambiguous and should be interpreted carefully. A positive result is observed in 75 to 85 percent of the population that are a chronic carrier of HCV, 15 to 25 percent in whom the infection has been resolved, and also in a few who have been recently infected (acute infection). After getting infected with HCV, the antibodies can be detected usually after at least 6–8 weeks or even longer especially in individuals with suppressed immune systems (like in HIV patients). An infection that has been present for less than 6 months may not be detected with an antibody test. It takes more than 6 months for the infection to test positive.
Screening for Hepatitis D and E
Hepatitis D virus (HDV) antibodies (anti-HDV IgG and IgM), which appear approximately 4 weeks after exposure to the virus can be used to screen for HDV. On the contrary, specific anti-HEV IgM antibodies are useful in detection of HEV in the blood.
Further Evaluation
People who test positive for the antibody screening tests usually undergo additional tests to get more insights. The most common follow-up tests include qualitative or qualitative viral loads (RNA or DNA tests). The qualitative test determines whether the virus is present while the quantitative test measures the amount of the virus present in the blood.
Conclusively, although elimination of viral hepatitis has been a global priority owning to the increasing burden, insufficient diagnostic work-up remain a major challenge. A substantial scale up in the rates of diagnosis and access to treatment is an immediate requirement to meet the World Health Organization’s global targets of reduction in incidence rate of viral hepatitis.
Agilus Diagnostics, a subsidiary of Fortis Healthcare Limited
