INTERPRETATION OF SEROLOGIC TESTING IN PATIENTS WITH Hepatitis B Virus INFECTION.

 

GLOSSARY OF HEPATITIS B TERMS

        HBV: HBV is a spherical particle with a diameter of 42 nm. Its outer shell (or envelope) is composed of several proteins known collectively as HBs or surface proteins (indicated by “s”). The outer shell, frequently referred to as the surface coat, surrounds an inner protein shell, composed of HBc protein (indicated by “c”). The inner shell is referred to as the core particle or capsid. Finally, the core particle surrounds the viral DNA and the enzyme DNA polymerase.

        HBsAg (Hepatitis B Surface Proteins): The outer surface coat composed of Hepatitis B surface proteins is produced in larger quantities than required for the virus to reproduce. The excess surface proteins clump together into spherical particles of between 17 and 25 nm in diameter but also form rods of variable length. In some cases, these particles encapsulate a core particle and produce a complete and infectious virus particle that enters the bloodstream and can infect other liver cells. The excess spheres, rods, and also complete viral particles enter the bloodstream in large numbers and are easily detectable. Hepatitis B surface protein is detectable in the bloodstream before the patient mounts an antibody response. HBsAg clears from the bloodstream as the infection resolves.

        HBeAg (Hepatitis B e Protein): HBeAg is a peptide and is normally detectable in the bloodstream when HBV is actively reproducing. This, in turn, leads to the person being much more infectious and at a greater risk of progression to liver disease. The exact function of this nonstructural protein is unknown. HBeAg is usually detectable at the same time as HBsAg and disappears before HBsAg disappears. The presence of HBeAg in chronic infection indicates that HBV is actively reproducing and there is a higher probability of liver damage. Hepatitis B e protein levels parallel HBsAg levels and indicate active viral replication.

        HBcAb (Hepatitis B core Antibody): The first detectable antibody to appear around 8 weeks after infection with HBV is antibody to the HBV core protein. HBcAbs persist in serum after an infection with HBV has been defeated, and testing for this antibody has been used to detect previous exposure to the live virus. The presence of both HBcAb IgM and HBcAg in the bloodstream is diagnostic of acute infection.

        HBsAb (Hepatitis B surface Antibody): These are generally the last antibodies to appear. HBsAb can neutralize the Hepatitis B virus and their appearance can be taken as an indicator that an initial infection has been defeated. HBsAb can also be induced to appear by vaccination to provide protection against Hepatitis B.

        HBeAb (Hepatitis B e Antibody): Antibodies to the “e” antigen (HBeAb) normally appear a few weeks after HBeAg is no longer detectable. The presence of HBeAb generally indicates a favorable prognosis.

        Anti-HBc window: The period of time after the appearance of HBcAb IgM and after the disappearance of HBsAg, but prior to the appearance of HBsAb. In this case, the presence of HBcAb IgM is the only serologic marker for acute infection.

 INTERPRETATION OF SEROLOGICAL TESTING IN PATIENTS WITH HBV INFECTION.

HBsAg	HBsAb	HBcAb	HBeAg	HBeAb	Possible interpretation
+	−	IgM	+	−	Acute HBV infection, highly infectious
+	−	IgG	+	−	Chronic HBV infection, highly infectious
+	−	IgG	−	+	Late acute or chronic HBV infection, low infectivity
+	+	IgG/ IgM	+/−	+/−	1. HBsAg of one subtype and heterotypic anti-HBs (common)  or      2. Process of seroconversion from HBsAg to anti-HBs (rare)
−	−	IgM	+/−	+/−	1. Acute HBV infection 2. Anti-HBc window
−	−	IgG	−	+/−	1. Low-level HBsAg carrier 2. Remote past infection 3. False positive
−	+	IgG	−	+/−	Recovery from HBV infection
−	+	−	−	−	1. Immunization 2. Possible remote infection 3. False positive