The next step in hepatitis testing
Worldwide, hepatitis continues to pose a significant health problem. Early diagnosis and treatment is one way in which its spread can be reduced. At Abbott’s hepatitis symposium, industry and clinical experts presented updates on the latest advances in hepatitis testing, focusing on hepatitis B virus (HBV) and hepatitis C virus (HCV). Here Xchange takes a closer look at a key strand of discussion, antigen testing.
Hepatitis in numbers New HBV infections occur in around 7 out of every 100,000 of the UK population every year1 and worldwide it’s the tenth leading cause of death. Around two billion people globally have been infected with HBV.2 An estimated 400,000 people in the UK have the HCV virus, but only 70,000 have been diagnosed. Treatment of HCV becomes harder the later the diagnosis.3
Testing methods A definitive diagnosis of viral hepatitis can only be achieved by using virus specific hepatitis tests. Clinicians also rely on these results to identify, differentiate, and monitor hepatitis infections. A variety of approaches are available including immunoassay methods such as antibody or antigen testing, or molecular testing for the presence of viral nucleic acid (DNA or RNA).
Abbott has a long history of virology testing and, for ARCHITECT, has developed one of the most comprehensive infectious disease menus available.
Antibody testing detects the patient’s antibodies to the virus. However, for hepatitis C it may take up to 70 days for these antibodies to appear (seroconversion) so antibody tests have limited use in detecting new infections. Also, they do not indicate current viraemia or elimination of virus from the patient. Immunoassays targeting viral antigen(s), however, can be used during the early stages of infection (figure 1), closing the seroconversion window period.
Figure 1. Schematic representation of seroconversion using HCV as an example
Transmission
Hepatitis B
Transmission is via contact with the blood or other body fluids of an infected person, most commonly during young adulthood by sexual activity and injecting drug use.2
Hepatitis C
HCV is spread through contact with infected blood. In the UK, more than 90% of newly diagnosed infections are contracted via sharing needles to inject drugs.4 Almost half of injecting drug users are now infected.5
In the innovative ARCHITECT HCV Ag assay, antigen is detected in the presence of HCV antibodies due to a pre-treatment step which causes lysis of viral particles and dissociation of antigenantibody complexes. Active HCV infection can be ruled out in cases of anti-HCV or HCV Ag/Ab reactivity if the HCV Ag result is negative.
For HBV, a panel of immunoassays is available to detect the presence of HBV (figure 2). Again, antigen testing can detect early infection, in this case using hepatitis B surface antigen (HBsAg).
ARCHITECT HBsAg Qualitative and Quantitative assays are designed to meet laboratories’ needs whether they are performing a quantitative test for therapeutic monitoring or require a high specificity test for screening purposes.
Figure 2. Acute hepatitis B diagnostics profile6
• Hepatitis B surface antigen (HBsAg) – detects acute or chronic
hepatitis B infection
• Antibody to hepatitis B core antigen (Anti-HBc) – detects previous
hepatitis B infection
• Antibody to HBsAg (Anti-HBs) – detects immunity to hepatitis B
• Hepatitis B type E antigen (HBeAg) – detects chronic, contagious hepatitis B
infection or acute infection
References:
1 BBC http://www.bbc.co.uk/health/conditions/hepatitisb1.shtml Accessed 30/06/09
2 WHO Factsheet 204. Hepatitis B. http://www.who.int/mediacentre/factsheets
Accessed 30 Jun 2009
3 BBC News. http://news.bbc.co.uk/go/pr/fr/-/1/hi/health/7827199.stm Accessed 30/06/09
4 Health Protection Agency. Hepatitis C in the UK: HPA Annual Report 2008
5 Health Protection Agency. Shooting Up: Infections among injecting drug users in the United
Kingdom 2007, An update: October 2008
6 Abbott Diagnostics. Hepatitis Learning Guide. www.abbottdiagnostics.co.uk Accessed 30/06/
