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Hepatitis B Surface Antigen General Clinical
Tests
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Test Name
Method |
Hepatitis B Surface Antigen, Total Anti- HBs, HBsAg
|
Specimen
Requirements |
Serum
Stable for 7 d at RT and indefinitely at 4° C or - 20°C. |
Ref. Range
Conventional
International Recommended Units |
Negative
Limits of detection: 0.02-1.0 ng/mL;
Typical positive quantitation 10(4)-10(5) ng/mL
|
Chemical Interfaces
In Vivo Effects |
None Found;
|
| Diagnostic Information |
HBsAg is the surface lipoprotein coat of the Hepatitis B virus. It was
originally discovered by Blumberg and was called Australian anitgen. Hepatitis
B is a retrovirus of the Hepadnavirdae family that can cause persistent
infection leading to cirrhosis and hepatocellular carcinoma. It has a unique
partially double-stranded circular DNA which utilizes the same nucleotide
sequences to code for different proteins by frame-shifting. The virus infects
hepatocytes, which then produce complete viral particles as well as excess
HBsAg. The Hepatitis B virus is not cytopathic. Instead, the host immune
reaction to foreign viral proteins lyses infected hepatocytes and causes
hepatitis. Because of immature host immunity, infected neonates and young
children are much more likely to become chronic carriers of the Hepatitis
B than adults. HBsAg compromises three proteins, (SHBs, encoded by the S
domain of the Hepatitis B genome; MHBs, encoded by S+preS1; and LHBs, encoded
by by S+preS1+preS2). Detection of HBsAg is usually the first detectable
marker of Hepatitis B infection and remains positive in persistent infections.
Therefore, HBsAg should be tested in the clinical settings of both acute
and chronic patients. |
| Remarks |
HBsAg produced by recombinant DNA techniques in yeast is used as a highly
effective vaccine. Original vaccines used purified HBsAg harvested from
chronic Hepatitis B carriers.
Quantitation of HBsAg is possible but not usually performed. With acute
Hepatitis B a 50% drop in HBsAg serum concentrations after one month indicates
resolving infection, whereas an increase implies persistence.
A number of reports have documented chronic Hepatitis B infections without
HBsAg detectable in serum. Although this is rare, the presence of the
virus can be deduced by testing for anti-HBc, anti-HBs, and HBV-DNA.
|
References:
Clinical Guide to Laboratory Tests, third edition.
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